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Assessing the potential for reductions in Irish local authority residential energy consumption: A case study of the efficacy of thermal envelope upgrades in a sample of Wicklow County Council’s housing stock.

Robert Wyse

MSc Climate Change and Sustainable Development

Institute of Energy and Sustainable Development De Montfort University September 2012


Abstract It is recognised that the energy performance of the Irish housing stock is poor, with ambitious retrofitting targets seen as essential to achieving legally binding energy consumption and CO2 emissions reductions targets. Local authorities are retrofitting their housing stocks, and are not only subject to stringent energy reduction targets, but are expected to play the role of market maker and encourage the uptake of retrofitting measures in their area.

This research focuses on Wicklow County Council. Based on the analysis of a sample of 718 dwellings from their stock, it is evident that the energy performance of an average Wicklow County Council dwelling is considerably worse than the average dwelling in Co. Wicklow or Ireland. In the absence of an overarching strategy for retrofitting, the retrofitting interventions employed by Wicklow County Council are considered on a per-dwelling basis and are driven by external energy assessors. An analysis of the efficacy of the thermal envelope in Wicklow County Council dwellings, coupled with an analysis of recommended retrofit interventions, reveals a failure to address significant areas of heat loss, and hence energy consumption.

Using a purpose built Excel based model, the impact of upgrading the thermal envelope to differing thermal standards on energy consumption and CO2 emissions in the sample of dwellings was investigated. Reductions in primary energy consumption of between 23% and 50% and in CO2 emissions of between 24% and 52% are deemed achievable, with potential Government funding of between â‚Ź2.3 million and â‚Ź7.8 million available depending on the thermal standard adopted.

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Acknowledgements And now, after so many months of working on a piece that must be structured ‘just so’, I shall write freely of my thanks to those who have helped me complete this body of work. From De Montfort University, I thank my supervisor, Dr. Andrew Wright. What I have produced I’m sure is quite different to what you had originally envisaged when you suggested retrofitting as a research topic for one of your students (Lessons learned from Retrofitting, anyone?), and I thank you for granting me free reign to craft this dissertation as I saw fit. Your advice over the last year or so has been of immense benefit to me. I’m not quite sure it is the norm for someone to command over an hour of your time on the phone, yet I did on several occasions, and it was most helpful. Your understanding and swift actions when I requested a short extension were most appreciated for the peace of mind they afforded me. From Wicklow County Council, I thank Breege Kilkenny for agreeing to let me carry out this research in the first place, and Alan Martin for providing the plethora of source materials that enabled it. Al, it is staggering to think that this work stemmed from our chance meeting on the Long Hill waiting for a bike race! Our frequent discussions gave me the insight I needed to complete this report, and I truly hope it is of some benefit to you. I’m fairly sure the next cuppa is on me. The fulfilment of this dissertation has coincided with a most difficult time in my personal life. Step forward Mam and Dad, and my sisters Cathy, Emma, Jenny and Fiona. I may never be able to adequately express how invaluable your support has been to me over the past few months. The effort in trying to complete this work given my circumstances quite literally nearly broke me, but with your help, it did not. Thank you. William Power; you inspired me to undertake this Masters in the first place. There have been times over the years when I couldn’t quite say I was thankful to you for that, but now that it's at a close, I can honestly say that I am a more complete person for having done this. And for that, I am in your debt. Auntie Carmel; I have never forgotten your words on how, in order to complete this course, I would draw upon the same mental and physical strength I drew upon when cycling competitively. Prescient is not the word. And Auntie Rioghnach; when I bemoan the time and effort this course has demanded of me, your advice on how the years would have passed anyway gives me much needed perspective and dare I say, makes me smile. Thank you both for your encouragement over the years.

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Paul Price; would you believe that in the end, I never got to use WUFI or Therm in anger!! Not to worry. I truly enjoy our 'sustainability rants' which have played no small part in shaping this work. The best of luck over the next month or so as you work towards completing your own dissertation and please, call on me to review as I called on you. And last, but absolutely by no means least; Mike Clarke. You are a Gent. Please take a bow, Sir. I cannot thank you enough for your patience and guidance as I endured the painstaking process of constructing the model used in this study (which, absurdly, was never even included in my original plan!). I hope you'll agree it was worth it. Forgive me, but I simply cannot resist; Dim NumPintsOwed As Integer NumPintsOwed = 1

And now to rest And now to heal And get my life Back to even keel

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Table of Contents Table of Figures ...................................................................................................................................... ix Table of Tables ....................................................................................................................................... xi Abbreviations ........................................................................................................................................ xii Section 1. Introduction ........................................................................................................................ 1 1.1

Context .................................................................................................................................... 1

1.2

Background ............................................................................................................................. 2

1.2.1

Energy Performance of Buildings Directive .................................................................... 2

1.2.2

The Fabric First Approach ............................................................................................... 4

1.2.3

Wicklow County Council ................................................................................................. 5

1.3

Aims and Objectives................................................................................................................ 7

1.4

Research Questions ................................................................................................................ 7

1.5

Methodology........................................................................................................................... 8

1.6

Dissertation Structure ............................................................................................................. 8

Section 2. Literature Survey ................................................................................................................. 9 2.1

Introduction ............................................................................................................................ 9

2.2

Drivers for retrofitting in the Irish context ............................................................................. 9

2.2.1

Contributions to energy consumption and CO2 emissions ............................................. 9

2.2.2

Legally binding emission reductions targets ................................................................. 11

2.2.3

Import Dependency ...................................................................................................... 13

2.2.4

Employment .................................................................................................................. 13

2.2.5

Fuel Poverty .................................................................................................................. 13

2.3

Energy performance of the Irish housing stock .................................................................... 14

2.3.1

Regulatory non-compliance .......................................................................................... 14

2.4

Typical Retrofit Interventions in Ireland ............................................................................... 17

2.5

Principles of the Fabric First Approach ................................................................................. 19

2.5.1

Insulated building envelope .......................................................................................... 19

2.5.2

Minimal Thermal Bridging............................................................................................. 19 vi


2.5.3

Highly air-tight thermal envelope ................................................................................. 21

2.5.4

Ventilation..................................................................................................................... 22

2.5.5

Moisture management ................................................................................................. 22

2.6

Workmanship ........................................................................................................................ 23

2.7

Key Findings .......................................................................................................................... 24

Section 3. Methodology ..................................................................................................................... 25 3.1

Research Strategy ................................................................................................................. 25

3.2

Data Sources ......................................................................................................................... 25

3.2.1

Wicklow County Council ............................................................................................... 25

3.2.2

Sustainable Energy Authority of Ireland ....................................................................... 25

3.3

Research Model .................................................................................................................... 26

3.3.1

DEAP Calculations ......................................................................................................... 26

3.3.2

Profiling Energy Performance and Thermal Envelope Efficacy ..................................... 27

3.3.3

Modelling retrofit interventions ................................................................................... 28

3.3.4

Model Simplifications and Limitations .......................................................................... 31

3.3.5

Model Accuracy – Individual Dwelling .......................................................................... 32

3.3.6

Model Accuracy – All Dwellings .................................................................................... 33

3.4

Data Quality .......................................................................................................................... 34

3.5

Research Limitations ............................................................................................................. 35

Section 4. Model Output & Data Analysis ......................................................................................... 37 4.1

Physical Profile ...................................................................................................................... 37

4.1.1

Sample Size ................................................................................................................... 37

4.1.2

Dwelling Age ................................................................................................................. 37

4.1.3

Dwelling Type ................................................................................................................ 38

4.1.4

Number of Storeys ........................................................................................................ 38

4.1.5

Structure Type............................................................................................................... 38

4.2

WCC Dwelling Energy Performance Overview...................................................................... 39

4.2.1

Average Energy Consumption and CO2 emissions ........................................................ 39 vii


4.2.2

BER Profile ..................................................................................................................... 40

4.2.3

Key findings ................................................................................................................... 42

4.3

Detailed Energy Consumption Analysis ................................................................................ 43

4.3.1

Thermal Envelope Performance ................................................................................... 45

4.3.2

Key Findings .................................................................................................................. 58

4.4

Recommended Interventions Analysis ................................................................................. 59

4.4.1

Sample Creation ............................................................................................................ 59

4.4.2

Sample Analysis............................................................................................................. 59

4.4.3

Payback and Energy reductions .................................................................................... 61

4.4.4

Key Findings .................................................................................................................. 62

Section 5. Scenario Analysis............................................................................................................... 63 5.1

Scenario Definition................................................................................................................ 63

5.1.1

Ventilation..................................................................................................................... 63

5.1.2

Element Thermal Transmittance................................................................................... 64

5.1.3

Thermal Bridging ........................................................................................................... 65

5.2

Scenario Output .................................................................................................................... 66

5.2.1

Primary Energy Consumption ....................................................................................... 66

5.2.2

Thermal Envelope Performance ................................................................................... 67

5.2.3

CO2 Emissions Reductions ............................................................................................. 73

5.2.4

BER Profiles ................................................................................................................... 74

5.2.5

Funding Achievable ....................................................................................................... 75

5.2.6

Key Findings .................................................................................................................. 77

Section 6. Conclusions ....................................................................................................................... 79 6.1

Further Research................................................................................................................... 81

References ........................................................................................................................................... 82 Appendix A – Data Quality .................................................................................................................... 89 Appendix B – Thermal Bridging ‘Y-Factors’ ........................................................................................... 91

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Table of Figures Figure 1 A sample Building Energy Rating (BER) Certificate (SEAI, 2007) ............................................... 3 Figure 2 Energy Flow in Ireland, 2010................................................................................................... 10 Figure 3 Ireland's GHG Abatement Cost Curve, 2030 ........................................................................... 11 Figure 4 Purchased Heat Energy and Home Energy Rating over time .................................................. 16 Figure 5 Reductions in thermal transmittance at ground floor / external wall junction where external insulation stopped at ground level (left) and continued underground (right) (Little a, 2009)............. 20 Figure 6 Mould risk associated with differing approaches to wall insulation ...................................... 23 Figure 7 The 5 steps of a DEAP Assessment ......................................................................................... 26 Figure 8 Extract from the Master Spreadsheet .................................................................................... 29 Figure 9 The use of Attribute Controls to update energy related planar element attributes .............. 30 Figure 10 Revised Wall related Heat Loss Calculation .......................................................................... 31 Figure 11 Dwelling Age Profile .............................................................................................................. 37 Figure 12 Dwelling Type Profile ............................................................................................................ 38 Figure 13 Average Primary Energy Consumption (left) and CO2 Emissions (right) ............................... 39 Figure 14 BER Profile for dwellings in Ireland, Co. Wicklow and WCC ................................................. 40 Figure 15 Distribution of Assessed and Expected Energy Ratings ........................................................ 41 Figure 16 Primary Energy Consumption (left) and CO2 Emissions (right) breakdowns ........................ 43 Figure 17 Primary Energy Consumption per age band ......................................................................... 44 Figure 18 Primary Energy Consumption (kWh/yr) per BER .................................................................. 44 Figure 19 Total Assessed Heat Loss Breakdown ................................................................................... 45 Figure 20 Air Change rates for average dwellings in Ireland, Co. Wicklow and WCC........................... 46 Figure 21 Average Ventilation Heat Loss per Dwelling Type ................................................................ 47 Figure 22 Contributions to Total Fabric Area, Total Planar and Total Fabric Heat Loss ....................... 48 Figure 23 Assessed contributions to Fabric Heat Loss .......................................................................... 48 Figure 24 Floor Type and Heat Loss profile........................................................................................... 49 Figure 25 Roof Type and Heat Loss profile ........................................................................................... 50 Figure 26 Roof Insulation Profile........................................................................................................... 50 Figure 27 Wall Type and Heat Loss profile............................................................................................ 51 Figure 28 Window Type and Heat Loss profile ..................................................................................... 52 Figure 29 Frame Type profile ................................................................................................................ 53 Figure 30 Elemental U-value comparisons (W/m2K) ............................................................................ 54 Figure 31 Thermal Bridging contribution to Fabric Heat Loss .............................................................. 55 Figure 32 Average Heat Loss Parameter per dwelling type .................................................................. 56 Figure 33 Average Net Space Heat Demand per dwelling type ............................................................ 57 ix


Figure 34 Breakdown of recommended interventions ......................................................................... 60 Figure 35 Recommended Interventions per BER .................................................................................. 60 Figure 36 Reductions in Total Space Heating Consumption and Primary Energy Consumption .......... 66 Figure 37 Disaggregated reductions in thermal envelope heat loss .................................................... 67 Figure 38 Reductions in ventilation heat loss ....................................................................................... 68 Figure 39 Disaggregated reductions in planar heat loss ....................................................................... 69 Figure 40 Reductions in Thermal Bridging heat loss ............................................................................. 70 Figure 41 Reductions in Heat Loss Parameter for each scenario ......................................................... 71 Figure 42 Reductions in NSHD for each scenario.................................................................................. 72 Figure 43 Reductions in CO2 emissions in each scenario ...................................................................... 73 Figure 44 Assumed BER profiles for each scenario ............................................................................... 74 Figure 45 Number of dwellings per funding bracket per scenario ....................................................... 75

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Table of Tables Table 1 Typical Irish Retrofitting Interventions..................................................................................... 18 Table 2 Air permeability values from various Irish sources .................................................................. 21 Table 3 DEAP Dwelling Report contents ............................................................................................... 27 Table 4 Energy related quantities considered in this study .................................................................. 28 Table 5 Retrofit Interventions and Modelled Attributes ...................................................................... 29 Table 6 Interventions assumed during Model testing .......................................................................... 32 Table 7 Model Test Results ................................................................................................................... 33 Table 8 Model Accuracy ........................................................................................................................ 34 Table 9 Inconsistent Age Bands ............................................................................................................ 35 Table 10 Expected Energy Ratings ........................................................................................................ 41 Table 11 Sample Recommended Interventions .................................................................................... 59 Table 12 Recommended Thermal Envelope Interventions per BER ..................................................... 61 Table 13 Average energy savings, costs and payback times for recommended interventions ............ 62 Table 14 Ventilation related limiting factors ........................................................................................ 63 Table 15 Assumed values of thermal transmittance ............................................................................ 64 Table 16 Assumed Thermal Bridging Factors ........................................................................................ 65 Table 17 Allocation of funding according to energy reductions achieved ........................................... 75 Table 18 Funding available for each scenario ....................................................................................... 76 Table 19 Overview of reductions achieved for all scenarios ................................................................ 77

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Abbreviations ac/h

Air changes per hour

BEH

Better Energy Homes

BER

Building Energy Rating

CO2

Carbon Dioxide

DEAP

Dwelling Energy Assessment Procedure

DECLG

Department of the Environment, Community and Local Government

DCENR

Department of Communications, Energy and Natural Resources

EC

European Commission

EP

European Parliament

EPA

Environmental Protection Agency

EPBD

Energy Performance of Buildings Directive

ETS

Emissions Trading Scheme

EU

European Union

GDP

Gross Domestic Product

GHG

Greenhouse Gas

GWh

Giga-Watt hour

kgCO2

Kilo-gram

kWh

Kilo-Watt hour

LZC

Low to Zero Carbon

m2

Meters squared (area)

m3

Meters cubed (volume)

MPEPC

Maximum Permitted Energy Performance Coefficient

MPCPC

Maximum Permitted Carbon Performance Coefficient

MtCO2eq

Mega tonnes of Carbon Dioxide equivalent

MVHR

Mechanical Ventilation and Heat Recovery

NBERRT

National BER Research Tool

NERP

National Energy Retrofit Program

Pa

Pascals

RET

Renewable Technologies xii


SAP

Standard Assessment Procedure

SEAI

Sustainable Energy Authority of Ireland

SEI

Sustainable Energy Ireland

sqm

Square Meter (area)

TGD

Technical Guidance Document

WCC

Wicklow County Council

yr

Year

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Section 1. Introduction 1.1 Context In 2010, the Irish residential sector was responsible for 27% of total final energy consumption and 12.7% of greenhouse gas (GHG) emissions. Given these sizeable contributions, the residential sector is seen as an important contributor towards the achievement of Irish obligations regarding GHG emissions under the Kyoto protocol and European Climate and Energy packages. The stated goal of the National Energy Retrofit Program (NERP) is to reduce the energy consumption of dwellings in Ireland by an average of 42% by 2020. The NERP is essential to the success of the National Energy Efficiency Action Plan (NEEAP), itself devised to achieve Ireland’s obligations under the European Climate and Energy Package. As part of the NEEAP, local authorities are obliged to increase energy efficiency by 33% by 2020, far in excess of the 20% required for the nation as a whole (DCENR, 2009, p. 8). As custodians of 6% the national housing stock, Irish local authorities are undertaking widespread residential retrofits in an effort to meet such targets. Studies such as that carried out by Wardell & Shanks (2005) suggest that the efficacy of the thermal envelope in Irish dwellings is poor, with high levels of ventilation heat loss and widespread deficiencies in insulation. Poor workmanship and regulatory non-compliance are deemed contributing factors to this situation which has resulted in the energy consumption of Irish dwellings exceeding European norms. It is understood that reductions in CO2 emissions in the region of 90% are achievable in the Irish residential sector, however retrofitting measures employed to date in Ireland are insufficient to deliver such reductions. Taking Wicklow County Council (WCC) as a case study, this research investigates the reductions in energy consumption and CO2 emissions achievable across a sample of dwellings should the principles of the fabric first approach be implemented, and a focus be placed solely on the thermal envelope whilst retrofitting.

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1.2 Background 1.2.1

Energy Performance of Buildings Directive

The EU Directive on the Energy Performance of Buildings (EPBD) was adopted into Irish law in 2006. Two principle aims of this directive are to provide a common methodology for calculating the energy performance of a building and to provide a system of certification that makes the energy consumption of a building readily available to the public (EC, 2003). Based on IS EN 13790, and drawing heavily on the UK Standard Assessment Procedure (SAP), the Dwelling Energy Assessment Procedure (DEAP) is the official Irish procedure for calculating and assessing the energy performance of a dwelling and is fully compliant with the methodology framework set out in the EPBD (SEAI a, 2008). The main steps carried out as part of a DEAP survey are described in section 3.3.1.

A DEAP assessment results in the issuance of a Building Energy Rating (BER) certificate, which indicates the annual primary energy consumption and CO2 emissions of the building. As shown in Figure 1 (below), ‘A’ rated dwellings (consuming less than 75 kWh/m2/yr) are the most energy efficient, with ‘G’ rated ones (consuming more than 450 kWh/m2/yr ) the least;

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Figure 1 A sample Building Energy Rating (BER) Certificate (SEAI, 2007)

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1.2.2

The Fabric First Approach

Energy consumption in houses is complex, depending on building geometry, the thermal characteristics of the building envelope and therefore by extension, the external climate. The ultimate aim of retrofitting dwellings in Ireland must be to create a housing stock which provides a healthy and comfortable environment for occupants and whose energy consumption is greatly reduced relative to present levels and largely independent of the vagaries of the Irish climate. A distinction is made between the thermal and building envelopes; the physical components of the building envelope – the planar elements such as doors, floors, roof, walls and windows - combine to form the thermal envelope, which is the enclosure that holds warm or cold air in a structure (Energy Vortex, n.d.). The fabric first approach emphasises reducing space heating demand to the minimum possible level by optimising the thermal envelope in terms of air-tightness and heat retention. The principles underlying this approach are discussed further in section 2.5 The fabric first approach clearly underlies Irish building regulations for new dwellings (DECLG, 2011), is championed by the Energy Savings Trust in the UK (EST a, 2010) and is the foundation for both Code for Sustainable Homes (BRE Trust, 2010) and Passivhaus (Schnieders & Hermelink, 2006) standards. The fabric first approach is equally applicable to retrofits, with Davies & Osmani (2011, p. 1694) noting its widespread adoption in the UK. In recognition of the fact that achieving the Passivhaus standard whilst retrofitting is extremely challenging primarily owing to the difficulties in achieving low levels of thermal bridging heat loss and high levels of air-tightness with an existing structure (Hearne, 2012), the Passivhaus Institute have devised the EnerPHit standard for retrofits, the central tenet of which is a fabric first approach (Feist, 2010). For several reasons, the fabric first approach should be of interest to local authorities in general and WCC in particular.

Wardell & Shanks (2005, p. VI) note how local authority tenants have the highest occupancy ratio, and therefore the highest energy consumption of all tenure types, thus reductions in space heating demand achieved through retrofitting will be most fully exploited by this occupant type. As outlined in section 2.5, optimising the thermal envelope should minimise space heating demand, tackle fuel poverty, ensure good indoor air quality is maintained and eliminate issues relating to mould growth arising from thermal bridging and surface condensation, where present. Upgrading heating systems as part of a retrofit will reduce space heating demand and CO2 emissions (particularly where a solid fuel system or inefficient boiler is replaced) and may alleviate instances of fuel poverty. However, 4


replacing heating systems at the expense of optimising the thermal envelope means current and future heating loads are not minimised, and health benefits accruing from envelope optimisation are not realised; an approach not strictly aligned with WCC’s aim to improve the quality of life of its tenants (Sheehy, 2004, p. 17).

A failure to capitalise on the benefits afforded by the fabric first approach necessitates that the building fabric be revisited at a later date to upgrade its performance. Given the potentially long lead time in revisiting dwellings for a second retrofit, health issues and unnecessarily high space heating related energy consumption and CO2 emissions may persist for some time to come, as noted in (EST b, 2010, p. 4). This approach is not aligned with Irish government policy to maximise energy savings to clients and avoid the necessity of undertaking further costly energy upgrade works at a later stage (DEHLG a, 2010, p. 2). The expectation has been set that local authorities should lead by example, and act as market makers and exemplars in the promotion of the energy performance of buildings (Neary, n.d.). In Wicklow, a county where the average dwelling energy consumption is 14.8% above the national average (see section 4.2.1 for further details) and that ranks 20th out of 26 counties for retrofitting grant applications (SEAI a, 2012, p. 1), this is a vital role for WCC to fulfil. Finally, the approved re-cast of the EPBD (EP, 2012) states that by 2018, all new buildings owned or occupied by local authorities will need to consume ‘nearly zero’ energy, with extant energy consumption met via renewable sources. Though no target is explicitly set for existing buildings becoming ‘near zero’, there is a clear indication that this may occur in the future, with local authority buildings likely leading the way. An optimised thermal envelope provides the ideal platform for renewable energies and hence the adoption of the fabric first approach puts in place a strong foundation for such an eventuality. 1.2.3

Wicklow County Council

Wicklow County Council is one of 4 local authority housing providers in the administrative area of County Wicklow, which is located on the east coast of Ireland. Perhaps reflective of the level of construction activity in Ireland in the opening decade of the 21st century, WCC’s housing stock grew from 1,740 units in 2004 (Sheehy, 2004, p. 10) to between 2,297 (WCC, 2008) and 2,334 (WCC a, 2011) units by 2008, with 90% of dwellings deemed to be in ‘Good’ or ‘Reasonable’ condition (Sheehy, 2004, p. 24). This however refers to the general, maintained condition of the stock and bears no relation to its energy performance.

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In response to government directives, WCC are now placing a strong emphasis on energy efficiency, and commenced a widespread retrofitting effort in 2010. The first phase of this was to establish the baseline energy performance of their stock, with Building Energy Rating (BER) Assessors invited to carry out dwelling energy assessments (WCC b, 2011). A total of 15 assessors were chosen for the first tranche of assessments which considered 1,973 dwellings, with each assessor being assigned circa 131 dwellings (WCC c, 2011). Like other Irish local authorities, WCC receive partial funding for retrofitting work from central government as part of the Social Housing Investment Program (SHIP), with the amount allocated per dwelling based on reductions in energy consumption achieved (DEHLG b, 2010). Sheehy (2004, p. 36) notes that where retrofitting work is carried out, it must meet the standard defined by the building regulations currently in force.

As per government guidance, the retrofitting interventions

implemented by WCC are not confined to the building fabric, and can relate to space and water heating systems also (WCC d, 2011). Crucially, and unlike other local authorities such as Tipperary or Carlow/Kilkenny County Councils for example, WCC do not enjoy the support of a local energy agency with which they can devise an overall retrofitting strategy. From private communications with Mr. Alan Martin, a representative of the Housing department in WCC, it is further understood that; •

There is a lack of understanding of how energy is consumed across the stock

There is an shortage of knowledge and expertise regarding building physics and thermal envelope optimisation

Techniques such as thermal bridging analysis, condensation analysis, thermal imagery and air-tightness testing are not routinely used during retrofits

In the absence of an overall retrofitting specification, the interventions implemented for any of the dwellings vary based on recommendations provided by BER Assessors

With specific reference to the thermal envelope, it is unclear to WCC how effective recommended interventions are at mitigating heat loss, and hence energy consumption, across the stock

There is a preference for internal insulation over external insulation, primarily as this can be undertaken by internal staff

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1.3 Aims and Objectives Given the acknowledged absence of assistance from any external agency, and the general lack of knowledge of energy consumption across the stock, this research aims to profile the energy performance of WCC’s dwellings, highlight the impact that the adoption of the fabric first approach could have on energy consumption and CO2 emissions, and ultimately, contribute to the development of an overarching retrofitting strategy. To achieve these aims, several objectives have been identified; 1. Profile the physical characteristics, energy performance and thermal envelope efficacy of a sample of WCC’s housing stock 2. Analyse a sample of the retrofitting interventions performed by WCC 3. Model the impact of various thermal envelope retrofit strategies on the primary energy requirement and CO2 emissions of the sample 4. Extrapolate the impact on stock-wide primary energy requirement and CO2 emissions

1.4 Research Questions To meet the aims and objectives, several research questions have been compiled; 1. What are the physical attributes of dwellings in WCC’s housing stock? 2. In terms of energy consumption and CO2 emissions, how does the average WCC dwelling compare to the average dwelling in Co. Wicklow or Ireland? 3. How well does the thermal envelope of WCC dwellings perform – what are the areas of significant heat loss? 4. Are the retrofit interventions being suggested to WCC addressing these areas of significant heat loss? 5. If the fabric first approach was fully embraced, what is the scale of reductions in energy consumption and CO2 emissions achievable?

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1.5 Methodology This will be a desk based study taking as input a sample of Dwelling Energy Assessment Procedure Survey reports supplied by Wicklow County Council.

1.6 Dissertation Structure This report is divided as follows; Literature Survey; an overview of the drivers for and status of retrofitting in Ireland is presented, alongside an overview of the state of the Irish housing stock. The principles underlying the fabric first approach are discussed. Methodology; an outline of the methodology employed for this research is presented, along with a description of the model used to facilitate scenario analysis. Model Output & Data Analysis; a detailed analysis of the energy performance of the sample and recommended retrofitting interventions is presented. Scenario Analysis; the impacts of upgrading the thermal envelope in dwellings across the sample to differing standards are discussed. Conclusions: concluding remarks are presented along with suggested topics for further research.

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Section 2. Literature Survey 2.1 Introduction This section discusses the drivers for retrofitting in an Irish context and describes retrofitting Interventions typical to Ireland. The principles of the fabric first approach, and its relevance to retrofitting, are discussed. Irish and European policy is drawn upon, with statistics on energy consumption and CO2 emissions obtained from authoritative sources such as the Sustainable Energy Authority of Ireland (SEAI) and the Environmental Protection Agency (EPA). Detailed reports on the energy performance of the Irish housing stock are used to provide further context.

2.2 Drivers for retrofitting in the Irish context When considering the drivers for retrofitting in an Irish context, it is useful to begin with the contribution of the residential sector to overall Irish energy consumption and GHG emissions. 2.2.1

Contributions to energy consumption and CO2 emissions

As illustrated in Figure 2 (below), the residential sector is a major energy consumer, second only to the transport sector, and in 2010 was responsible for 22% of total primary energy requirement and 27% of total final consumption (SEAI a, 2011, p. 15);

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Figure 2 Energy Flow in Ireland, 2010

The sector’s contribution to GHG emissions is less significant at 12.7% (7.42 MtCO2eq), with only the waste sector contributing less (EPA a, 2012, p. 2). Overall Irish GHG emissions were 0.7% lower in 2010 than in 2009, an artefact of the on-going economic recession (ibid, p. 1). The harsh winter of 2010 led to an increase in residential related GHG emissions of 5.3% (ibid, p. 8) and an increase in residential related energy use of 5.9% (SEAI a, 2011, p. 4). However, climate corrected residential energy consumption reduced 2.9% on 2009 figures (ibid, p. 4), something which serves to highlight the impact of climate on Irish residential energy consumption. Historically, through the retrofitting of dwellings and other measures, the residential sector “strongly influenced” (Odyssee, 2011, p. 1) a 9% improvement in the Irish energy efficiency index between 2000 and 2008. Alongside a growing stock of more efficient new dwellings, these measures partially contributed to a decline of 24.4% in overall climate corrected energy consumption per dwelling during the period 1990 – 2010 (SEAI a, 2011, p. 69), however this reduction occurred against the backdrop of an increase in total dwelling numbers from 1,019,723 in 1991 (CSO, 1997, p. 40) to 2,004,175 in 2011 (CSO, 2011, p. 17), resulting in a long term climate corrected increase of 21.1% in residential energy consumption (SEAI a, 2011, p. 67), and a 12.1% increase in GHG emissions (ibid, p.68).

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Through sustained retrofitting, the increased implementation of Low to Zero Carbon (LZC) technology and the decarbonisation of the electricity grid, 90% reductions in CO2 emissions are deemed achievable in the residential sector by 2050 (SEAI, 2010, p. 5). Curtain (2009, p. 24) and Dineen et al. (2010, p. 2) note how retrofitting building fabric is one of the most effective and cost efficient ways to achieve energy savings in the Irish economy, a view reinforced by Motherway & Walker (2009, p. 4) in Figure 3 (below), which illustrates how this abatement opportunity incurs a negative societal cost;

Figure 3 Ireland's GHG Abatement Cost Curve, 2030

2.2.2

Legally binding emission reductions targets

Given its potentially significant contribution and evident cost effectiveness, residential retrofitting is seen as a key contributor in achieving compliance with legally binding obligations to reduce overall GHG emissions under the Kyoto protocol and the European Climate and Energy Package. Irish obligations under the Kyoto protocol are to limit GHG emissions to no more than 13% above 1990 levels by 2012 (DEHLG, 2007, p. 7). The National Climate Change Strategy illustrates how increased penetration of renewable heating, enhanced building regulations and energy efficiency

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improvements in local authority housing are the primary contributors from the residential sector towards Kyoto compliance (ibid, p. 9).

Emissions reductions owing to the economic recession, the permitted inclusion of the impact of forest sinks and governmental purchase of credits under the European Union Emissions Trading Scheme (EU-ETS) (EPA b, 2012, p. 3), mean this target, once seen as “extremely challenging” (DEHLG, 2006, p. 8), and first breached in 1998 (SEAI a, 2011, p. 29), now appears likely to be met. EC (2010) notes three legally binding targets central to the Climate and Energy Package agreed by the European Parliament and Council in December 2008; 1. A reduction in EU GHG emissions to at least 20% below 1990 levels 2. 20% of EU energy consumption to come from renewable resources 3. A 20% reduction in primary energy use compared with projected levels, to be achieved by improving energy efficiency Ireland’s obligations under the Effort Sharing Decision implemented to achieve agreed GHG reductions is for emissions in sectors of the economies not covered by the EU-ETS to be reduced to 20% below 2005 levels by 2020 (EP, 2009). Crucially however, the contribution of forest sinks is not permitted (EPA b, 2012, p. 12), thus the proportional reductions required from other participating sectors, including the residential sector, are increased. It should be noted that Irish local authorities manage 6% of the national housing stock (DECLG a, 2012). The National Energy Efficiency Action Programme (NEEAP) (DCENR, 2009) outlines Ireland’s plan of action to fulfill the agreed 20% reduction in primary energy use. From a requirement of 32GWh, this plan identifies savings of circa 24GWh, with circa 10.4GWh (44%) of these being identified in the residential sector alone. Long term trends indicate that as a result of the NEEAP, energy consumption in the residential sector could be 22.5% lower than projected levels in 2020 (SEAI b, 2011, p. 30). The 8GWh shortfall in energy savings is expected to be filled by way of the National Energy Retrofit Program (NERP), a central aim of which is to deliver energy efficiency upgrades to 1 million residential, public and commercial buildings by 2020 (DCENR, n.d., p. 8). It is anticipated that residential related GHG emissions will decrease by 33.8% between 2010 and 2020 as a result of NEEAP & NERP activity (EPA b, 2012, p. 17), yet overall compliance with EU 2020

12


emissions targets for non-ETS sectors is nonetheless expected to be missed by 4.1 – 7.8 MTCO2eq (ibid, p.4). Residential retrofitting is also seen as a way to tackle issues other than energy consumption and GHG emissions. 2.2.3

Import Dependency

Irelands energy import dependency was 86% in 2010 (SEAI a, 2011, p. 4), with imports costing the exchequer approximately â‚Ź6 billion in 2008 (DCENR, 2009, p. 8). SEAI (2010) highlights how retrofitting can contribute greatly to our energy independence and reduce Irish exposure to oil price volatility. 2.2.4

Employment

The construction sector once generated 24% of Irish GDP (Curtain, 2009, p. 14) and provided 20% of all jobs in the economy (DKMEC, 2010, p. iii). The recent economic contraction has seen employment in the sector return to 1998 levels (ibid). A sustained retrofitting programme could sustain 10,000 jobs over a 10 year period (SEAI, 2010, p. 5). 2.2.5

Fuel Poverty

Clinch & Healy (2001, p. 114) define fuel poverty to be an inability to heat the home to an adequate (safe and comfortable) temperature, owing to low household income and poor household energy efficiency. This is a widespread issue in Ireland, with over 20% of Irish households affected in 2009 (DCENR, 2011). Fuel poverty is associated with serious respiratory illnesses, with research suggesting that for every euro invested in energy poverty measures, 42 cents are returned in savings from health expenditure on all householders (ibid p. 32). Clinch & Healy (2001, p. 114) note how Ireland suffers from one of the highest rates of excess winter mortality in northern Europe, and link this with the poor thermal efficiency of the housing stock.

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2.3 Energy performance of the Irish housing stock Based on an analysis of 286,793 DEAP surveys, made accessible through the National BER Research Tool (NBERRT) (SEAI b, 2012), the average primary energy consumption for an Irish dwelling is 262.9 kWh/m2/yr., yielding a D2 rating. Thus, on average, the energy consumption of Irish dwellings must decrease 42% to achieve a C1 energy rating, the target rating for NERP and local authority related retrofitting work (Armstrong & Dowling, 2012, p. 1). Average CO2 emissions for an Irish dwelling are estimated to be 62.6 kgCO2/m2/yr. By way of international comparison, Irish dwellings in 2006 consumed 27% and 36% more energy than the average UK and European counterparts respectively. Similarly, the average Irish dwelling emitted 47% more CO2 than the average UK dwelling and 104% more than the average dwelling in the EU27 block of nations (SEAI b, 2008, p. 2). Several reasons are proffered for this poor performance; •

Larger dwelling size

Fuel use mix for space heating

Losses in the electricity grid

Both Scheer et al. (2012, p. 2) and DEHLG (c, 2010, p. 4) note rising expectations of internal temperatures as a factor while regulatory non-compliance has recently been identified as a significant driver in Irish dwelling energy consumption.

2.3.1

Regulatory non-compliance

Building regulations were first considered in Ireland in 1972 (Curtain, 2009, p. 20). It was only after the enactment in 1991 of the Building Control Act 1990 that mandatory regulations incorporating thermal standards came into effect. The Irish building regulations comprise a set of Technical Guidance Documents, each concerned with a different aspect of building control, with TGD Part LConservation of Fuel and Energy, the most relevant here. TGD Part L has been revised several times. Changes made in 2002 included reductions in the permitted thermal transmittance (U-value) of the building fabric planar elements (doors, floors, roofs, walls and windows) while more radical amendments in the 2008 and 2011 revisions mean dwellings built to standard should consume between 40% and 60% less energy than their 2005 counterpart, respectively.

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Headline revisions to Part L of the 2011 Building Regulations (DECLG, 2011) include;

Acceptable air permeability reduced from 10m³/h/m² to 7m³/h/m²

Required efficiency for Biomass boilers set at 77%, all other boilers increased to 90%

The Maximum Permitted Energy Performance Coefficient (MPEPC) set at 0.4

The Maximum Permitted Carbon Performance Coefficient (MPCPC) set at 0.46

It is understood that merely complying with minimum values of air permeability and meeting default U-values will not be sufficient to achieve required MPEPC and MPCPC values, thus at least some of the ‘backstop values’ will need to be exceeded to ensure regulatory compliance (Antonelli & Colley a, 2012).

In 2011, the national housing stock numbered 2,004,175 dwellings (CSO, 2011, p. 17), with 52.9% of these constructed prior to 1991 (DECLG b, 2012). Daly (2007) asserts that the large proportion of dwellings built in a non-regulated context is a significant factor in the poor performance of the Irish residential sector and in doing so, infers that the presence of building regulations will guarantee more efficient housing. Indeed, as much is assumed in (EPA, 2010, p. 12), which suggests enhanced building regulations will contribute a 20% reduction in residential sector GHG emissions by 2020.

However, the efficacy of building regulations is clearly linked with their enforcement, which in Ireland, falls under the remit of the City and County Councils. Inspections are only required for 12% – 15% of commencement notices, i.e. 85% of newly constructed homes are not required to be inspected under the issued guidelines (NCA, 2008, p. 3). Local government statistics indicate average nationwide rates of inspection varied from 23% to 33% over the period 2004 to 2010 (Power, 2012, p. 27).

Based on data from the NBERRT, Antonelli & Colley (b, 2012) claim that 21% of homes built under the 2005 regulations failed to meet its main requirements, while 67.7% of homes built under the 2008 regulations fail to meet all of its main requirements, indicating widespread non-compliance with regulations.

In a study of 150 residential units representative of national trends of dwelling age, built form and tenure of occupancy, Wardell & Shanks (2005) calculated a 41% reduction in theoretical energy rating for dwellings constructed between 1997 – 2002 compared with those constructed between

15


1961 and 1980 (pre-regulation era), a reduction attributable to successive improvements to Irish Building Regulations since 1979. However the study notes this theoretical reduction is not met with a corresponding reduction in actual energy consumption, which reduced by only 13%.

Figure 4 (below) illustrates how, for the sample as a whole, an increasing difference between Purchased Heat Energy (actual energy consumption) & Home Energy Rating (theoretical energy consumption) was noted amongst newer dwellings (ibid, p. 14);

Figure 4 Purchased Heat Energy and Home Energy Rating over time

While this phenomenon is partially attributed to occupant behaviour, it is further noted that, of the 52 dwellings in the study constructed between 1997 – 2002, no dwelling was fully compliant with Part L (Conservation of Fuel and Energy), Part F (Ventilation) and Part J (Heat Producing Appliances) of the Irish building regulations. Only 1 dwelling was fully compliant with Part L in every respect, 29 dwellings fully complied with Part F in every respect (ibid, p. 61) and 27 complied fully with Part J (ibid, p. 63).

2.3.1.1 Thermal envelope performance With specific reference to the efficacy of the building fabric, the report notes that based on a visual inspection, 87% of dwellings are compliant with insulation levels, with non-compliance usually attributed to inadequate attic insulation (ibid, p. 57). The report notes that: 16


“It was possible to measure wall insulation type and thickness accurately in the majority of dwellings, through unsealed openings for plumbing and electrical services, such as waste pipe openings and around the electricity meter box.” (ibid, p. VI).

The presence of unsealed openings as mentioned, along with poor on-site practice in failing to seal the void between dry lining and masonry walls at edges of openings such as doors, for example, contributes to the low level (15%) of infiltration compliance (ibid, p. 57). Low levels of compliance were also noted for pipe work insulation, with only 10% of dwellings in compliance (ibid, p. 57).

Infra-red thermography and air tightness tests were performed on a subset of 20 dwellings constructed predominately in the period 1997-2002 to supplement the findings of the visual inspection. This highlighted significant deficiencies (ibid, p. VII);

55% of dwellings had some insulation (typically roof or wall) missing

15% of the dwellings had extensive insulation missing

Local thermal bridging at window sills and lintels etc. was found in 66% of dwellings

Condensation risk mainly due to missing insulation was found in 33% of living rooms, bedrooms and wet rooms.

Average air permeability was recorded as being 11.8m3/hr/m2@50pa, 69% higher than good practice value of 7.0m3/hr/m2@50pa (ibid, p.39)

Excessive air leakage (ac/h > 0.5) was found in 37% of dwellings.

2.4 Typical Retrofit Interventions in Ireland The findings presented thus far suggest a significant improvement in the overall energy performance of the Irish housing stock is achievable through retrofitting. The NERP is being administered by the Sustainable Energy Authority of Ireland (SEAI), with grant assistance for residential energy efficiency interventions available through the Better Energy Homes (BEH) scheme. Statistics relating to energy efficiency interventions undertaken as part of the BEH scheme between March 2009 and July 2012 (SEAI c, 2012) are presented in Table 1 (below), alongside those reported as part of a survey of housing quality undertaken during 2001 – 2002 (Watson & Williams, 2003);

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Measure Roof Insulation Cavity Insulation Dry Lining (internal) Insulation External Insulation Replacement Windows External Doors High efficiency Boiler with heating controls upgrade Heating controls upgrade only Solar Heating Before / After BER Integral BER

SEAI (2012)

Watson & Williams (2003)

29% 24% 3% 3%

7%

2-3% 22% 19%

10% 3% 1% 4% 23%

Table 1 Typical Irish Retrofitting Interventions

Dineen et al. (2010, p. 8) distinguish between ‘shallow’ measures such as roof and cavity insulation and ‘deep’ measures such as heating controls upgrades and external insulation. SEAI (2010, p. 4) expand upon this by citing internal and external insulation, high efficiency windows and Mechanical Ventilation Heat Recovery (MVHR) as deep interventions. Though both sets of data in Table 1 (above) are not directly comparable (for example, double glazing is excluded from BEH on cost effectiveness grounds (Curtain, 2009, p. 19)), there is a clear bias towards shallow retrofit measures that are unlikely to achieve the 90% reductions in GHG emissions envisioned by SEAI (2010), a finding in keeping with Dineen et al. ( 2010, p. 8). A similar situation is noted in the UK by Davies & Osmani (2011, p. 1691). Despite administering the NERP, a scheme with an “easily achievable” (Curtain, 2009, p. 32) target BER of C1, SEAI (2010, p. 3) conclude there is a need to encourage ‘deep retrofits’, something for which there appears to be no single definition. Struabe offers a generic definition, holding a deep retrofit to be one which “extends the viability of the building 50 to 100 years into the future” (BSC, 2010, p. 6). Others define deep retrofits in terms of energy consumption reductions, with qualifying levels ranging from to 50% to 90% (Scania, 2010). Reductions in operating costs is also a commonly used measure, with Bloom & Wheelock (2010, p. 4) and Curtain & Maguire (2011, p. 4) assuming deep retrofits to achieve 60% and 40% reductions, respectively.

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2.5 Principles of the Fabric First Approach The fabric first approach is central to regulations governing the construction of new dwellings in Ireland and to the EnerPHit standard for deep retrofits, and as such, can be said be central to the achievement of the significant emissions reductions deemed possible in the Irish residential sector. Several interrelated principles underlie the fabric first approach; •

The building envelope should be highly and continuously insulated

Thermal bridging should be minimal

The thermal envelope should exhibit low levels of infiltration, yet be well ventilated

Moisture should be well managed

Given the constraints inherent in an existing structure, the achievement of these principles in a retrofit scenario can be challenging, particularly aspects relating to thermal bridging and infiltration. 2.5.1

Insulated building envelope

In creating highly insulated building envelope, the objective is to maximise reductions in the transmittance of heat through building envelope planar elements. The thermal transmittance of any such planar element is defined by its ‘U-value’, and is measured in W/m2K. Davies & Osmani (2011, p. 1692) note how, in the UK, improving thermal retention through thermal insulation of planar elements is the preferred retrofitting approach, possibly reflective of claims that the energy related attributes of a dwelling’s fabric have the greatest influence on space heating energy demand and define the extent of fabric and ventilation heat loss in a dwelling (Wardell & Shanks, 2005, p. 25). 2.5.2

Minimal Thermal Bridging

A principle consideration of the thermal envelope is that insulation levels should be as continuous as possible, with breaks in the continuity of the level of insulation giving rise to a thermal bridge; a localised area of reduced insulation, resulting in increased levels of thermal transmittance, hence a lower surface temperature which can facilitate mould growth (Little & Arregi, 2011). Aside from the health implications associated with mould growth, thermal bridge related heat loss can contribute significantly to overall dwelling heat loss. As thermal transmittance through planar elements decreases as a result of increasing levels of insulation, the proportion of overall heat loss attributable to thermal bridging increases. Further to this, (Little a, 2009) graphically demonstrates how the ill-management of thermal bridges can serve to increase the absolute thermal transmittance through them. Furthermore, it is demonstrated that significant reductions in thermal 19


transmittance through common thermal bridges as found at the eaves, window sills and jambs can be achieved given sufficient attention to detail. For example, where external insulation is dropped below ground level, thermal transmittance along the thermal bridge at the junction of ground floor and external wall (as indicated by Ψ in Figure 5 (below)1) can be reduced over 60%;

Figure 5 Reductions in thermal transmittance at ground floor / external wall junction where external insulation stopped at ground level (left) and continued underground (right) (Little a, 2009)

Through the use of thermal imagery, Wardell & Shanks (2005) determined that 13 dwellings from a sample of 20 contained thermal bridging in contravention of Irish building regulations, with 11 and 13 dwellings missing wall and roof insulation respectively. A brief discussion of how thermal bridging heat loss is accounted for by DEAP and the model used in this study is provided in Appendix B.

1

See Appendix B for further information on Ψ

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2.5.3

Highly air-tight thermal envelope

Wardell & Shanks (2005, p. 39) note that infiltration is air exchange that occurs through cracks and small gaps in the external fabric that are not designed in, such as spaces between window frames and external walls and small gaps around penetrations through the external envelope. A measure of infiltration is air permeability, which represents the volume of air passing through each square meter of building envelope (Sinnott & Dyer, 2012, p. 270). For new dwellings in Ireland, the limiting value of air permeability is 7m3/h/m2 (DECLG, 2011), a value far in exceedance of other European countries (EST a, 2010, p. 44). Table 2 (below) presents sample air permeability values for Irish dwellings derived from various sources;

Number of Tests Avg. m3/hr/m2 Max. m3/hr/m2 Min. m3/hr/m2

(Sedlak & Sheward, 2008) 32 8.1 20.8 2.1

(Sinnott & Dyer, 2012) 28 9.1 14.4 5.1

(O'Se, 2011) circa 120 5.0 23.0 0.3

Table 2 Air permeability values from various Irish sources

The maximum values noted here are far in excess of Irish best practice values, with the average values noted by Sedlak & Sheward (2008) and Sinnott & Dyer (2012) also failing to meet current regulations. O'Se (2011) notes the lower average and minimum values of air permeability result from air-tightness being ‘designed in’ to the dwellings being tested. Values of air permeability of 0.82 m3/hr/m2 have been recorded for dwellings retrofitted to the EnerPHit standard (EST, 2011, p. 31), a figure which highlights the significant scope for reductions in infiltration related heat loss in Irish dwellings. In terms of reducing heat losses via infiltration during retrofits, O'Se (2011) notes that renovated dwellings did not necessarily see significant improvements in air-tightness, though he does not mention what interventions were undertaken during renovations. Sedlak & Sheward (2008) note that older, renovated dwellings showed the worst performance, even with new windows installed, a problem attributed to problems with joints between new and old constructions. Both findings are at odds with Sinnott & Dyer (2012, p. 272), who note that values of air-tightness in dwellings which had undergone a retrofit to be on average 35% better than for dwellings which had not, and note that cavity wall insulation and double glazing installation have the largest effect, reducing air permeability by 28% and 39% respectively.

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2.5.4

Ventilation

Whereas infiltration is uncontrolled air movement through the building envelope, ventilation is controlled air movement, and is required to ensure good indoor air quality is provided for occupants. Both Little (b, 2009) and Dimitroulopoulou (2012, p. 110) note the health impacts of poor ventilation, including the onset of respiratory problems such as asthma. The provision of adequate ventilation in low energy dwellings is a delicate act, balancing the need to maintain air quality and keep ventilation related heat losses to a minimum. For this reason, mechanical ventilation with heat recovery is mandatory for low energy standards such as EnerPHit (Feist, 2010, p. 8). 2.5.5

Moisture management

The need for adequate ventilation is furthered by Little & Arregi (2011) who note that humidity in Irish dwellings is higher than European norms, something which can lead to two types of condensation; surface and interstitial.

Wardell & Shanks (2005, p. 37) note that surface moisture condensation and mould growth can occur when the surface temperature is lower than the dew point temperature of the air in the room. Thus, surface condensation leading to mould growth can occur where relative humidity reaches 100% around a thermal bridge in an area where ventilation is poor. The possibility of such condensation problem arising was noted in approximately 33% of sample of 20 dwellings (ibid).

In discussing interstitial condensation, Little (a, 2010) focuses on walls, claiming them to be the planar element most supportive of mould growth. Mould growth can occur at 80% humidity, less than the 100% required for surface condensation (Little b, 2009). In an earlier age of high infiltration, little or no insulation and internal heat sources such as open fires, walls could dry out over time with little mould growth. When a wall is internally insulated, the wall structure cannot dry out, leading to the potential failure of the insulation system and internal mould growth on the wall (Little a, 2010). This situation can be avoided through the use of a suitable vapour control layer to limit the moisture reaching the internal faรงade of the wall behind the insulation (Little b, 2009) and the suitable impregnation of the external faรงade of the wall to prevent rain ingress (Little b, 2010).

Little & Arregi (2011) note how internal insulation at the party wall can lead to cold spots and potential mould growth in adjacent properties, as shown in Figure 6 (below);

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Figure 6 Mould risk associated with differing approaches to wall insulation

Note how in Figure 6 (left), the use of external insulation means the wall in House A remains warm, with the temperature in the corner of House B raised locally. Note the temperature factor (fRsi), which must be maintained above 0.75 to remove the risk of mould growth. In Figure 6 (right) internal insulation has been used in House A, which lowers the temperature in the corner of House B and brings the temperature factor below 0.75, introducing the risk of mould growth. External insulation keeps materials within the thermal envelope warm and dry, preventing condensation and mould problems (Little & Arregi, 2011). Instances of thermal bridging are also lower with external insulation, which is mandatory for the EnerPHit standard, with Internal insulation only permitted for 25% of wall area where external insulation is not practical or permitted (Feist, 2010, p. 6).

2.6 Workmanship EST (2011) and makes clear the level of detail required to achieve EnerPHit levels of air permeability. Little (a, 2009) and EST (b, 2010) clearly emphasise the need for high levels of design and workmanship in order to significantly reduce thermal bridging heat loss during a retrofit. Taking a more holistic view, Sinnott & Dyer (2012, p. 273) conclude that quality workmanship, design, detailing and construction practice are all essential to successful retrofitting, while (EST b, 2010) highlights the importance of each team recognising the centrality of their work to the achievement of a low energy retrofit.

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2.7 Key Findings The residential sector is a major contributor to overall Irish energy consumption and CO2 emissions. Regulatory non-compliance and poor enforcement have combined to create the legacy of a housing stock where the average performance is considerably poorer than European norms. Evidence presented in this section suggests it would be unwise to assume newer dwellings do not require energy efficiency interventions. Although retrofitting to date has yielded results, the widespread uptake of deep retrofits is deemed necessary not only to achieve the magnitude of reductions in energy consumption and CO2 emissions deemed possible in the residential sector, but to the achievement of Ireland’s obligations under internationally binding emissions agreements. The fabric first approach has been shown to provide a suitable foundation for deep retrofits. The need for quality workmanship across all disciplines has been identified as a requirement to the successful achievement of low energy retrofits.

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Section 3. Methodology 3.1 Research Strategy Taking WCC as a case study, the strategy is to perform a desk based analysis of a sample of DEAP survey results. A custom built excel based model will be used to analyse the input files and perform scenario analysis.

3.2 Data Sources Two significant sources of primary data are Wicklow County Council and the Sustainable Energy Authority of Ireland. 3.2.1

Wicklow County Council

External, accredited assessors perform DEAP surveys for WCC, and as per WCC (b, 2011), must provide the following documents for each survey performed; 1. A copy of the BER certificate issued 2. A detailed report of the assessment exported from DEAP, in both Excel and XML format (the ‘Dwelling Report’) 3. An Excel file containing recommendations made by the assessor on energy efficiency interventions which could be implemented to achieve the target C1 energy rating for the dwelling (the ‘Energy Efficiency Report’) In total, 718 Dwelling Reports and 68 Energy Efficiency Reports provided by WCC are considered in this study. 3.2.2

Sustainable Energy Authority of Ireland

The SEAI is responsible for the administration of the Building Energy Rating (BER) scheme in Ireland and maintain the NBERRT, which contains the results of DEAP surveys carried out nationwide to date. Given that the inputs to this research and the data contained in the NBERRT were collected in an identical fashion (i.e. a standardised DEAP survey), use of this information facilitates a direct comparison between dwellings in WCC and those in Ireland and Co. Wicklow. At the time of use (July, 2012), this database contained 289,593 results, representing approximately 14.4% of the national stock. For comparative purposes, this study assumes the 286,793 non-

25


provisional2 entries to represent the average dwelling in Ireland, while the 8,465 non-provisional entries for dwellings in Co. Wicklow are deemed to represent the average dwelling in Co. Wicklow.

3.3 Research Model Key objectives of this research are to; 1) Profile the energy performance and thermal envelope efficacy of a sample of WCC dwellings 2) Model the impact on energy consumption of various thermal envelope retrofit strategies A custom model, based on the DEAP application used to perform dwelling assessments, has been created for this purpose. 3.3.1

DEAP Calculations

A DEAP survey is performed using the ‘DEAP’ software application, which is developed and maintained by the SEAI3. The calculations used by the DEAP application to determine primary energy consumption and CO2 emissions for a dwelling are fully accessible in (SEI, 2007). The DEAP process can be broken into several steps, as outlined in Figure 7 (below); Step 5. Determine total primary energy consumption (kWh/y) and CO2 emissions (kg/y) Space heating system(s) efficiency (%) and fuel type Water heating system(s) efficiency (%) and fuel type Renewable contributions Step 4. Determine Annual Space Heating Demand (kWh/y) Heating system controls Heating system responsiveness Presence and location of heating system(s) pumps and fans Step 3. Determine Net Space Heat Demand (kWh/y) Heat Capacity (thermal mass) of Dwelling (MJ/K) Average Internal Temperature (°C) Average Monthly External Temperature (°C) Step 1. Determine Overall Heat Loss Coefficient (W/K) Step 2. Determine Overall Heat Gains (W) Fabric Heat Loss (W/K) Ventilation Heat Loss (W/K) Internal Gains(W) Solar Gains (W) Thermal Bridging Factor (W/m2K) Number of openings (m3/h) Occupants (W) Window Orientation Heat Loss - Heat Loss - Heat Loss - Heat Loss - Heat Loss - Structural Infiltration (ac/h) Hot Water Glazing Transmittance Doors Floors Roofs Walls Windows Ventilation Method (ac/h) System (W) Frame Factor Area Area Area Area Area Number of sheltered sides Appliances (W) Standardised values U-value U-value U-value U-value Adjusted Lighting (W) of Monthly Insolation U-value

Figure 7 The 5 steps of a DEAP Assessment

Step 1: Determine the Overall Heat Loss Coefficient, which represents total dwelling heat loss by way of ventilation heat loss, planar heat loss and thermal bridging heat loss. Key inputs here relate

2

There are 3 BER types (SEAI d, 2012, p. 5); Provisional (required for a dwelling that is not yet built but is offered for sale “off the plans”), Final (required for a newly-built dwelling before it is occupied) and Existing (required for any existing dwelling that is offered for sale or to let). 3 This study assumes all dwelling assessments were performed using DEAP V3.1.0, the latest version available at the time WCC undertook their assessments.

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to the number of openings in the dwelling, building envelope element U-values and areas and a thermal bridging factor. Step 2: Determine Overall heat gains. Key inputs here relate to the number of lights in the dwelling. Step 3: Based on standardised assumptions of internal and external temperature, the thermal mass of the dwellings and solar gains, determine the Net Space Heat Demand (NSHD). Step 4: Accounting for the responsiveness of any heating system(s) and the presence of controls, pumps and fans, determine the Annual Space Heating Energy Requirement. Step 5: Accounting for space and water heating system efficiencies, fuel types used and the presence of any renewable technologies, determine the primary energy requirements and CO2 emissions for the dwelling. The effect of retrofit interventions on overall energy usage can also be modelled for individual dwellings through the DEAP application. The results of a DEAP survey can be exported to an Excel file (the ‘Dwelling Report’) containing the following information on separate tabs;

1) Dwelling overview information 2) Dwelling dimensions 3) Ventilation details 4) Planar element details 5) Heat Loss details 6) Water heating details 7) Solar water heating details

8) Lighting and internal gains 9) Annual Heat Use 10) Annual Space Heat Req. 11) Distribution system losses and gains 12) Heating system energy requirements 13) Summer internal gains 14) Dwelling energy requirements and CO2 emissions

Table 3 DEAP Dwelling Report contents

3.3.2

Profiling Energy Performance and Thermal Envelope Efficacy

In the context of this study, that DEAP can only analyse a single dwelling at a time is a key limitation, as this this research aims to analyse the performance of 718 dwellings.

To circumvent this

limitation, the 718 separate ‘Dwelling Reports’ provided by WCC were parsed using a custom built Excel Macro and collated into a single Excel ‘Master Spreadsheet’, which forms the basis of the model used to perform energy profiling and retrofit analysis. 27


Information central to determining the energy consumption and CO2 emissions for each dwelling in the sample is distilled to a single row in the master spreadsheet, thus facilitating data analysis. Table 4 (below) highlights specific energy related quantities central to profiling the energy performance of the sample; Assessed Quantity Ventilation Heat Loss Planar Element Heat Loss Thermal Bridging Heat Loss Fabric Heat Loss Overall Heat Loss Net Space Heat Demand Total Space Heating Primary Energy Demand Dwelling Primary Energy Demand Dwelling CO2 Emissions Table 4 Energy related quantities considered in this study

The analysis of these quantities is presented in section 4.

3.3.3

Modelling retrofit interventions

Upon creation, the data contained within the master spreadsheet is static, that is to say information contained in one cell is not linked in any way with information in any other cell. To model the impact on primary energy consumption and CO2 emissions arising from the implementation of various retrofit interventions, the calculations performed by the DEAP application must be incorporated into the master spreadsheet. The results of these calculations are represented by ‘modelled quantities’ which are implemented as columns in the master spreadsheet adjacent to the corresponding ‘assessed quantity’. Figure 8 (below) shows an extract of the master spreadsheet, with the assessed and modelled values of Fabric heat loss (FabricHeatLoss [W/K] and MFabricHeatLoss [W/K], respectively) clearly visible;

28


Figure 8 Extract from the Master Spreadsheet

As can be seen, this approach easily facilitates a comparison of ‘before and after’ values for a quantity, and allows reductions achieved to be determined for a quantity. The retrofit interventions the model aims to accommodate are listed in Table 5 (below). It is clear that the implementation of any of the listed interventions will alter the inputs to specific DEAP calculations. This is managed in the model by associating each retrofit intervention with a ‘modelled attribute’, also noted in Table 5 (below). The value associated with each modelled attribute can be manually defined via an ‘attribute control’, which is implemented as a dropdown containing values relevant to the intervention the modelled attribute represents. The values of modelled attributes are taken as input to the DEAP calculations embedded within the master spreadsheet. For Floors, Roofs, Walls and Windows, an attribute control is provided per element type to account for the fact that there may be several element types per dwelling. Intervention

Modelled Attribute

Alter the number of Chimneys Alter the number of Flues Alter the number of extract fans / open vents Alter the number of mobile gas appliances Improve draught-stripping measures Improve Door thermal performance Improve Floor thermal performance Improve Roof thermal performance Improve Wall thermal performance Improve Window thermal performance Reduce heat loss via Thermal Bridging

M#Chimneys M#OpenFlues M#Fans/Vents M#FluelessGas M%Draughtstripped MDoorUValue MFloorUValue MRoofUValue MWallUValue MFrameType, MGlazingType MBridgingFactor

Table 5 Retrofit Interventions and Modelled Attributes

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3.3.3.1 Example By way of example, consider the thermal upgrade of walls. Several types of wall are present in the sample; 300mm Cavity, 225mm Solid Brick etc. To be able to model the effect of upgrading the thermal transmittance of 300mm cavity wall to U-value = 0.27 W/m2K by way of external insulation for example, it must be possible to identify all instances of 300mm Cavity wall and then alter the U-value associated with each. Figure 9 (below) shows an extract of the data captured for Walls in the master spreadsheet, and the attribute control used to update Wall specific energy related attributes;

WallType 1 300mm Filled Cavity 300mm Cavity Timber Frame 300mm Cavity 300mm Cavity Stone 300mm Cavity

WallArea 1 WallUValue 1 MWallUValue 1 82.8 75.1 85.63 44.51 10.02 77.05 82.19

0.6 1.1 0.55 0.55 0.6 0.6 0.47

0.6 0.27 0.55 0.27 0.27 0.6 0.27

Figure 9 The use of Attribute Controls to update energy related planar element attributes

The master spreadsheet extract is interpreted as follows; •

WallType contains the varying types of wall as recorded during the DEAP assessment

WallArea contains the area associated with the wall type

WallUValue contains the U-Value of the wall type as recorded during the DEAP assessment

MWallUValue contains the value of the modelled attribute as selected in the ‘Walls’ attribute control (Figure 9, above, right). This control, located on a separate ‘Interventions’ worksheet in the master spreadsheet, allows a revised U-value be selected for each wall type present in the sample. By way of the Excel VLOOKUP function, the revised value for the modelled attribute is applied to all instances of the wall type associated with the modelled attribute. Note how if the attribute control selection is ‘No Change’ for a particular wall type, the value of the modelled attribute remains unchanged for that wall type (for example, see values of WallUValue and MWallUValue for the wall type ‘Stone’, above).

The suffix ‘1’ indicates that all values relate to the first wall type for the dwelling in question.

30


Note how in Figure 10 (below) the model has calculated a revised value of heat loss attributable to the wall type (MWallHeatLoss) as a result of the reduced U-value;

WallType 1

WallArea 1 WallUValue 1 MWallUValue 1 WallHeatLoss 1 MWallHeatLoss 1

300mm Filled Cavity 300mm Cavity Timber Frame 300mm Cavity 300mm Cavity Stone 300mm Cavity

82.8 75.1 85.63 44.51 10.02 77.05 82.19

0.6 1.1 0.55 0.55 0.6 0.6 0.47

0.6 0.27 0.55 0.27 0.27 0.6 0.27

49.68 82.61 47.0965 24.4805 6.012 46.23 38.6293

49.68 20.277 47.0965 12.0177 2.7054 46.23 22.1913

Figure 10 Revised Wall related Heat Loss Calculation

The method described above is used throughout the model to calculate reductions in heat loss attributable to ventilation, planar elements or thermal bridging. To better accommodate trouble shooting, calculations for planar elements are performed on dedicated worksheets in the master spreadsheet. 3.3.4

Model Simplifications and Limitations

Several simplifications are made in the model; •

DEAP default values are assumed consistent across all assessments

For ease of analysis, Ground Floor Apartments (45 dwellings), Maisonettes (7 dwellings) and Top Floor Apartments (36 dwellings) are modelled collectively as ‘Apartments’.

It is assumed that internal gains remain constant in all houses post-retrofit.

The model does not account for semi-exposed walls4.

The model does not account for roof windows, introducing a small error in the estimation of window related heat loss. See Appendix A for further details.

It is assumed that chimneys will only ever be blocked up, so the number of chimneys will only ever reduce.

Owing to the way in which retrofit interventions are modelled It is not possible to model the effect of retrofitting some incidences of an element; for any particular element build up, the model assumes all incidences to be upgraded.

4

An analysis shows that only 0.61% of total walled area is semi-exposed; heat loss through this walled area will be slightly overestimated in the model, though the error introduced will be insignificant overall.

31


Depending on the insulation strategy employed for walls, the thermal mass category of a dwelling may be altered during a retrofit (SEAI a, 2008, p. 90). Any such effects are not catered for in the model.

The model does not account for the use of mechanical ventilation systems which are mandatory in the EnerPHit standard (Feist, 2010, p. 8). This has two noticeable affects; firstly, reductions in ventilation heat loss will likely be underestimated by the model owing to the assumed presence of open vents for ventilation and secondly, energy consumption related to pumps and fans will remain unchanged and hence be underestimated.

Efficiency gains from replacing open fires with stoves are not accounted for, thus the model will slightly overestimate space heating energy consumption and associated CO2 emissions in some scenarios.

3.3.5

Model Accuracy – Individual Dwelling

The accuracy of the model at the individual dwelling level was validated by comparing its output to that of DEAP for a package of retrofit interventions as applied to a mid-terraced dwelling built during the 1980’s. The interventions assumed are outlined in Table 6 (below); Element Chimneys Doors Floors Roofs Walls Windows

Intervention Reduce from 2 to 1 Upgrade to U-value=1.5 No Change Double Insulation depth to 300mm Externally insulate, revised UValue=0.3 Upgrade to Triple-glazed, argon filled

Table 6 Interventions assumed during Model testing

32


Model test results are outlined in Table 7 (below); Quantity

Ventilation Heat Loss (W/K) Total Plane Heat Loss (W/K) Total Thermal Bridging Heat Loss (W/mK) Total Fabric Heat loss (W/K) Total Heat Loss (W/K) Net Space Heat Demand (kWh/y) Total Space Heat Primary Energy Req. (kWh/y) Total Primary Energy Req. (kWh/y) Total CO2 Emissions (kg/y)

DEAP As Assessed

Modelled ‘No Changes’

Difference

DEAP ‘With Changes’

Modelled ‘With Changes’

Difference

60

60

0.0%

51

51

0.0%

100

100

0.0%

63

62

-1.6%

20.7

20.7

0.0%

20.7

20.7

0.0%

120

121

0.8%

83

83

0.0%

180 5593

181 5580

0.6% -0.2%

134 3631

134 3654

0.0% 0.6%

9406

9288

-1.3%

6579

6367

-3.2%

16799

16682

-0.7%

14590

13761

-5.7%

3527

3502

-0.7%

3143

2868

-8.7%

Table 7 Model Test Results

For the ‘No Change’ scenario, variances are insignificant throughout. Small inaccuracies become exaggerated in the Interventions scenario, resulting in total primary energy requirement and total CO2 emissions being under-estimated by 5.7% and 8.8% respectively.

3.3.6

Model Accuracy – All Dwellings

The difference between the assessed value (as recorded during the DEAP assessment) and modelled values (as calculated by the model) for any quantity may vary per dwelling. Owing to simplifications in the model and rounding errors in Excel, quantities may be overestimated for some dwellings and underestimated in others. Cumulatively, these differences will introduce an error across the sample. To provide confidence in the model, it is required to know the scale of this error. Table 8 (below) outlines the accuracy with which the model replicates assessed values of each quantity assuming no retrofit interventions (i.e. the ‘No Changes’ scenario);

33


Quantity

Ventilation Heat Loss (W/K) Total Plane Heat Loss (W/K) Total Thermal Bridging Heat Loss (W/mK) Total Fabric Heat Loss (W/K) Total Heat Loss (W/K) Net Space Heat Demand (kWh/y) Total Space Heat Primary Energy Req. (kWh/y) Total Primary Energy Req. (kWh/y) Total CO2 Emissions (kg/y)

Average Modelled Value (AMV) 50 129 25

Root Mean Square (RMS) 0.4 0.7 0.0

RMS as % AMV

154 204 6703 13066

0.8 0.9 56.0 553.7

0.5% 0.4% 0.8% 4.2%

22444 5752

553.8 180.2

2.5% 3.1%

0.8% 0.5% 0.0%

Table 8 Model Accuracy

Average Modelled Value: The average value for each quantity, as derived by the model. Root Mean Square: The Root Mean Square of the difference between assessed and modelled values of the quantity for each dwelling. This accounts for the fact that the difference between assessed and modelled values may be positive or negative for any particular dwelling. RMS as a % of AMV: This provides context on the scale of inaccuracy inherent in the model. Overall, it can be seen that the model is quite accurate in replicating the assessed values of quantities, with total primary energy requirement and CO2 emissions being overestimated by 2.5% and 3.1% respectively.

3.4 Data Quality In terms of completeness and consistency, the data provided as input to this study was of very good quality. Several noteworthy items are discussed in Appendix A.

34


3.5 Research Limitations There are several limitations to this research; 1) Owing to time constraints and to reduce the likelihood of co-ordinating a large body of data from disparate sources, WCC is the only local authority considered in this study. The methods used are nonetheless equally applicable to other local authorities.

2) It was intended that a suitable scaling factor be used to extrapolate primary energy and CO2 emissions reductions across the stock, based on those achieved for the sample. This requires the identification of a dwelling attribute which is captured for each dwelling in the sample and accurately recorded for each dwelling in WCCâ&#x20AC;&#x2122;s housing stock. Energy related attributes such as dwelling age or type are immediately identified as being suitable. However, dwelling type is not captured for every dwelling in the stock, and while a year of construction could be ascribed to each dwelling based on internal WCC methodology, this methodology is not consistent with that used in DEAP (see Table 9, below), meaning comparison is impossible. DEAP Age Band (SEAI, 2008) A <1900 B 1900 - 1929 C 1930 -1949 D 1950 - 1966 E 1967 - 1977 F 1978 - 1982 G 1983 - 1993 H 1994 - 1999 I 2000 - 2004 J >2005

WCC Age Band (Sheehy, 2004) <1960 1960 - 1964 1965 - 1969 1970 - 1974 1975 - 1979 1980 - 1984 1985 - 1989 1990 - 1995 1995 - 1999 >2000

Table 9 Inconsistent Age Bands

3) An in-depth analysis of the reductions in heat loss through thermal bridging, and an analysis of potential issues with surface or interstitial condensation arising from the implementation of retrofitting interventions, was to have been performed. However, the scale and quality of the data set received from WCC meant a more detailed analysis of energy consumption and heat loss could be performed than was originally planned, something deemed to be of greater initial value to WCC.

35


4) A lack of indicative ‘Y-Factors’ mean estimates of reductions in heat loss arising from thermal bridges may vary greatly to what can be achieved in practice.

5) The format in which data was received made it difficult to compile a more comprehensive sample for ‘Recommended Interventions’ analysis.

36


Section 4. Model Output & Data Analysis This section is based on the output of the model described in section 3.3, and aims to provide an overview of the energy performance of WCCâ&#x20AC;&#x2122;s housing stock. Physical attributes of the dwellings, such as age, construction type and number of storeys are considered first. Headline indicators of dwelling energy performance, such as energy consumption, CO2 emissions and BER are then considered, before a detailed analysis of thermal envelope performance is presented. An analysis of recommended energy efficiency interventions completes the section.

4.1 Physical Profile 4.1.1

Sample Size

As noted earlier, WCCâ&#x20AC;&#x2122;s stock is estimated to number between 2,297 and 2,334 dwellings. Assuming the median value of 2,316, the sample of 718 dwellings represents 31% of the stock. 4.1.2

Dwelling Age

Using the standard DEAP age bands to facilitate consistent data analysis, the age profile of the sample is shown in Figure 11 (below); 30%

25%

20%

15%

10%

5%

0%

Total

A-D ('00'66)

E ('67-'77)

F ('78-'82)

G ('83-'93)

H ('94-'99)

I ('00-'04)

J ('05+)

1.4%

16.6%

9.2%

26.5%

18.8%

12.8%

14.8%

Figure 11 Dwelling Age Profile

37


In keeping with national trends as noted in DECLG (b, 2012), circa 53% of dwellings pre-date the introduction of the 1991 building regulations, which were the first to formally consider dwelling thermal performance, and are expected to have poorer energy performance than those built under more stringent regulations. 4.1.3

Dwelling Type

Figure 12 (below) illustrates how the largest category of dwelling is semi-detached, with mid-terrace and end of terrace dwellings also contributing heavily to the sample. As would be anticipated for a local authority, detached dwellings contribute least. 40% 35% 30% 25% 20% 15% 10% 5% 0% Total

Semi-detached

Mid-terrace

End of terrace

Apartment

Detached

37.9%

26.6%

19.4%

12.3%

3.9%

Figure 12 Dwelling Type Profile

4.1.4

Number of Storeys

The majority of dwellings (74%) are 2 storey, while 24% are 1 storey units. 2% of dwellings have converted attics, and are classified as 3 story dwellings. 4.1.5

Structure Type

The sample is predominantly of masonry structure, with timber frame dwellings comprising only 4.6% of the sample. All timber frame units were constructed post 2000. 6.4% of the 285,583 dwellings recorded in the NBERRT at the time of writing were of timber frame construction.

38


4.2 WCC Dwelling Energy Performance Overview This section provides an overview of the energy performance of dwellings in the sample in terms of average primary energy consumption, average CO2 emissions and overall BER rating. For WCC dwellings, this information is obtained from the model described in section 3.3. To provide context, the average energy performance of dwellings in Co. Wicklow (8,465 dwellings) and Ireland (286,793 dwellings) is drawn from the NBERRT. 4.2.1

Average Energy Consumption and CO2 emissions

As shown in Figure 13 (below, left), average primary energy consumption for Irish dwellings stands at 262.9 kWh/m2/yr, placing them towards the upper end of the D2 energy band. Average primary energy consumption for dwellings in Co. Wicklow is 7.2% more (281.7 kWh/m2/yr), placing them firmly in the centre of the D2 energy band. Dwellings in the WCC sample consume on average 301.7 kWh/m2/yr, placing them in the E1 energy band. Thus, WCC dwellings consume 7.1% more than the average dwelling in Co. Wicklow, and 14.8% more than the average Irish dwelling. 310 300 290 280 270 260 250 240

kWh/m²/yr

100 80 60 40 20 0

Ireland

Co. Wicklow

WCC

262.9

281.7

301.7

kgCO2/m²/yr

Ireland

Co. Wicklow

WCC

62.6

67.7

77.7

Figure 13 Average Primary Energy Consumption (left) and CO2 Emissions (right)

Figure 13 (above, right) shows the national average CO2 emissions for a dwelling to be 62.6 kgCO2/m2/yr, with the average dwelling in Co. Wicklow emitting 8.2% more (67.7 kgCO2/m2/yr). The average WCC dwelling emits 77.7 kgCO2/m2/yr, 14.8% more than the average dwelling in Co. Wicklow, and 24.2% more than the national average.

39


4.2.2

BER Profile

The BER profile for dwellings in Ireland, Co. Wicklow and WCC is shown in Figure 14 (below); 25%

20%

15%

10%

5%

0% Ireland

A1

A2

A3

B1

B2

B3

C1

C2

C3

D1

D2

E1

E2

F

G

0.0% 0.0% 0.4% 1.8% 4.2% 8.4% 11.1% 12.4% 13.0% 13.1% 11.8% 6.7% 5.2% 5.1% 6.7%

Co. Wicklow 0.0% 0.0% 0.8% 1.7% 3.2% 6.8% 9.3% 11.0% 12.7% 13.4% 11.9% 7.5% 6.4% 6.4% 9.0% WCC

0.0% 0.0% 0.0% 0.0% 0.0% 1.8% 3.8% 7.7% 14.3% 20.1% 14.8% 11.4% 7.2% 7.7% 11.3% Figure 14 BER Profile for dwellings in Ireland, Co. Wicklow and WCC

There are proportionately more WCC dwellings in lower energy bands (C3 to G), with proportionately fewer in higher bands (C2 to A1), indicating the performance of WCC dwellings is comparatively poor across all bands. Overall, 94% of dwellings considered in this study are currently below the NERP target energy rating of C1. Contributing factors to this situation are discussed further in section 4.4. To further illustrate the energy performance of the sample, a methodology similar to that used by Curtain (2009, p. 38), can be used to derive expected energy ratings for dwellings in the sample based on the builing regulations in place at the time of construction. The expected BER for dwellings built under successive regulatory regimes are listed in Table 10 (below);

40


DEAP Age Band A-D ('00-'66) E ('67-'77) F ('78-'82) G ('83-'93) H ('94-'99) I ('00-'04) J ('05+)

Applicable Building Regulations NA 1972 1976 1982 1992 2002 2005

% Sample constructed in age band

Expected BER

18% 9% 26% 19% 13% 15%

E2 D2 D1 C2 C1 B3

Table 10 Expected Energy Ratings

Figure 15 (below) presents the distribution of expected and assessed energy ratings for the sample; 30% 25% 20% 15% 10% 5% 0%

B3 C1 C2 (2005) (2002) (1992)

Assessed BER

2%

4%

8%

Expected BER

15%

13%

19%

C3 13%

D1 D2 (1982) (1976) 20%

15%

26%

9%

E1 11%

E2 (1972)

F

G

7%

8%

11%

18%

Figure 15 Distribution of Assessed and Expected Energy Ratings

Considerably fewer dwellings than anticipated built post-1992 achieve the energy rating expected of them, with 47% of dwellings expected to meet or exceed a C2 rating, and only 14% of dwellings doing so. A degree of movement around expected ratings is anticipated over time as dwellings undergo retrofits, making it difficult to form a view of how this trend persists for older dwellings, though it does seem apparent. Issues highlighted in Wardell & Shanks (2005) and Antonelli & Colley (2012) relating to regulatory non-compliance can be considered contributory factors here. The accepted practice of building dwellings to the preceding standard for some time following the introduction of revised building regulations (SEAI a, 2008, p. 83) may be another driver for this trend.

41


4.2.3

Key findings

From the analysis presented above, it is clear the energy performance of the average WCC dwelling is below that of the average dwelling in Co. Wicklow, which in turn is below that of the average Irish dwelling. The low level of retrofitting grant applications in Co. Wicklow, as noted in SEAI (c, 2012), may be indicative of a low level of retrofitting work in general across the county, indicating WCC could influence behaviour by playing the role of market maker. The poor performance of WCC dwellings may be partly attributable to comparatively poor thermal envelope performance, something discussed further in section 4.3.1. The significant difference in assessed and expected energy ratings for more recently constructed WCC dwellings is in line with findings of widespread non-compliance highlighted by Antonelli & Colley (2012). Assuming the sample to be representative of WCCâ&#x20AC;&#x2122;s entire stock, the scale of the retrofitting challenge facing WCC becomes clear when it is considered that 94% of dwellings in the sample have an energy rating below the C1 target rating.

42


4.3 Detailed Energy Consumption Analysis An aim of this study is to quantify the impact that the implementation of fabric first approach can have on energy consumption across the sample of WCC dwellings. The performance of the thermal envelope is only one of many factors that determine a dwellingâ&#x20AC;&#x2122;s BER. It is expected, though not necessarily guaranteed, that where a BER is poor, the performance of the thermal envelope is also poor. Thus, it is of interest to profile energy consumption in the sample to determine the proportion of consumption attributable to the performance of the thermal envelope. Primary energy consumption is the focus of this analysis, as a dwellingâ&#x20AC;&#x2122;s BER is based on this quantity. Based on information output from the model, Figure 16 (below) demonstrates that the majority (59%) of energy consumed across the sample relates to space heating, something directly related to the performance of the thermal envelope5;

3%

3%

Space Heating

7%

Space Heating

7%

Water Heating

Water Heating 31% 59%

Lighting

30% 60%

Pumps and Fans

Lighting Pumps & Fans

Figure 16 Primary Energy Consumption (left) and CO2 Emissions (right) breakdowns

Water heating is also shown to be a significant contributor to energy consumption at 31%. Pumps and fans, which, given that 100% of the sample is naturally ventilated, can reasonably be assumed to be related to heating systems and kitchen hood appliances, contribute only 3% of the consumption, with lighting contributing 7%. CO2 emissions are shown to be similarly distributed across the sample.

5

The fuel used to provide heat and occupant behaviour are noted as drivers for space heating energy consumption, though both are excluded from this research.

43


Figures 17 and 18 (below) illustrate how the dominant contribution of space heating to overall energy consumption holds regardless of dwelling age or BER rating; 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

A-D ('00'66)

E ('67'77)

F ('78'82)

G ('83'93)

H ('94'99)

I ('00-'04)

J ('05+)

Pumps & Fans (kWh/y)

6,831

71,847

41,374

120,374

83,201

61,242

64,011

Lighting (kWh/y)

17,491

215,873

117,665

267,429

222,546

168,182

182,122

Water Heating (kWh/y)

57,838

1,211,980 550,307 1,495,570 820,512

518,497

438,126

Space Heating (kWh/y)

301,064 2,444,737 937,398 1,878,732 1,801,213 1,131,154 944,449

Figure 17 Primary Energy Consumption per age band

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

B3

C1

C2

C3

D1

D2

E1

E2

F

G

Pumps & Fans

6,339

13,202

35,798

77,400

98,099

75,903

56,278

31,850

25,764

28,247

Lighting

27,987

49,009

97,680

180,448 231,704 170,004 129,498

83,849

90,370

130,759

Water Heating

50,616

100,807 240,884 538,098 761,039 618,663 547,835 396,147 597,602 1,241,139

Space Heating

105,136 224,335 498,390 1,008,081 1,504,526 1,248,360 1,194,646 907,244 958,560 1,789,469 Figure 18 Primary Energy Consumption (kWh/yr) per BER

44


No instances of renewable technologies were noted during the dwelling assessments, thus space heating is, by virtue of its exclusive dependence on fossil fuels, the primary driver of CO2 emissions. CO2 emissions are shown to have a similar distribution across dwelling types and age bands as primary energy consumption. 4.3.1

Thermal Envelope Performance

The retrofit interventions considered in this study relate solely to the thermal envelope, a valid and justified approach given the centrality of the thermal envelope to space heating demand, and the centrality of this demand to overall energy consumption and CO2 emissions, as demonstrated above. This section aims to highlight the efficacy of the thermal envelope in the dwellings comprising the sample by analysing trends in heat loss. 4.3.1.1 Total Heat Loss Heat escapes the thermal envelope in several ways, most notably via ventilation (both controlled ventilation and uncontrolled infiltration), via conduction through planar elements and via thermal bridging. Based on an analysis of the data provided as performed by the model, the relative contributions of each type of heat loss to total assessed heat loss across the sample are as follows;

12% 25%

Ventilation Heat Loss Planar Heat Loss

63%

Quantity Ventilation Heat Loss (W/K) Planar Heat Loss (W/K) Thermal Bridging Loss (W/mK)

Thermal Bridging Loss

Assessed Value 35,885 92,689 17,983

Figure 19 Total Assessed Heat Loss Breakdown

As expected, and in line with Wardell & Shanks (2005), heat loss through the planar elements dominates, with ventilation related losses accounting for a quarter of all heat lost. Thermal bridging contributes 12%.

45


4.3.1.2 Ventilation Heat Loss The data suggests that infiltration arising from the physical characteristics of the dwellings such as the number of storeys and structure type is responsible for approximately 55% of ventilation related heat loss in the sample, with approximately 45% owing to the presence of openings, such as chimneys. Based on data from the NBERRT, average air change rates for dwellings in Ireland (7,221 dwellings considered), Co. Wicklow (166 dwellings considered) and WCC dwellings are shown in Figure 20 (below); 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 ac/h

Ireland

Co. Wicklow

WCC

0.30

0.33

0.79

Figure 20 Air Change rates for average dwellings in Ireland, Co. Wicklow and WCC

Several contributing factors for this comparatively poor performance of WCC dwellings are suggested; •

Figures for dwellings in Ireland and Co. Wicklow include results of air permeability tests, which are inherently more accurate than the DEAP algorithm upon which the WCC values are exclusively based (no air-tightness test values were noted in the sample).

The average number of chimneys (for which DEAP applies the largest penalty of all openings) for dwellings in Ireland (0.35) and Co. Wicklow (0.2) is significantly lower than for dwellings in WCC (1.0)

There are proportionally more timber frame dwellings (deemed more air-tight then masonry structures in DEAP) in Ireland (10%) and Co. Wicklow (12%) than WCC (5%)

46


Figure 21 (below) illustrates how average ventilation heat loss (W/K) varies per dwelling type in the sample of WCC dwellings; 60 50 40 30 20 10 0

W/K

End of terrace

Mid-terrace

Semidetached

Detached

Apartment

56

53

52

49

30

Figure 21 Average Ventilation Heat Loss per Dwelling Type

An examination of underlying data reveals that ventilation heat loss correlates strongly with dwelling volume, with End of Terrace dwellings having the largest volume (209m3), and hence heat loss, followed by Semi-detached (204m3), with Apartments having the smallest volume (116m3) and heat loss.

47


4.3.1.3 Fabric Heat Loss Fabric heat loss consists of heat loss by way of planar elements combined with that lost via thermal bridging. The contribution of each planar element to total element area, total planar and total fabric heat loss across the sample is shown in Figure 22 (below). The contribution of thermal bridging to fabric heat loss is also shown. Note how each planar elementâ&#x20AC;&#x2122;s contribution to fabric heat loss is less than that to planar heat loss as a result of the inclusion of thermal bridging. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Contribution to Total Fabric Area

Contribution to Total Planar Heat Loss

Thermal Bridging

Contribution to Total Fabric Heat Loss 16.2%

Windows

7.3%

23.0%

19.3%

Walls

38.3%

40.8%

34.2%

Roofs

26.7%

13.8%

11.5%

Floors

26.2%

16.7%

14.0%

Doors

1.5%

5.6%

4.7%

Figure 22 Contributions to Total Fabric Area, Total Planar and Total Fabric Heat Loss

The assessed contributions to fabric heat loss are as follows; Heat Loss Type Door Heat Loss (W/K) Floor Heat Loss (W/K) Roof Heat Loss (W/K) Wall Heat Loss (W/K) Window Heat Loss (W/K) Thermal Bridging Heat Loss (W/mK)

Assessed Value 5,216 15,519 12,765 37,833 21,346 17,983

Figure 23 Assessed contributions to Fabric Heat Loss

An interpretation of this data along with a detailed analysis of contributing factors is now presented.

48


4.3.1.3.1 Doors By contributing 1.5% of total building fabric area across the sample and 4.7% of fabric heat loss, doors are, per unit area, the worst performing planar element in terms of heat retention. Their small cumulative area however ensures absolute heat loss is less than any other element6. 4.3.1.3.2 Floors Floors account for 26% of building fabric area but only 14% of fabric heat loss. As illustrated in Figure 24 (below), the data suggests approximately 96% of this heat loss is attributable to the floor type ‘Ground Floor – Solid’. 120%

100%

80%

60%

40%

20%

0%

Ground Floor Solid

Exposed / Semi Exposed

Ground Floor Suspended

Partially Heated Below

Area

96.6%

0.5%

2.8%

0.1%

Heat Loss

96.0%

0.7%

3.0%

0.3%

Figure 24 Floor Type and Heat Loss profile

4.3.1.3.3 Roofs Roofs account for 27% of total fabric area and 11.5% of fabric heat loss. Somewhat un-intuitively, more heat is lost across the sample through floors than roofs, a phenomenon likely due to a greater presence of attic insulation than the presence of floor insulation. Similar to floors and as noted in Figure 25 (below), a high degree of uniformity is seen in the roof type profile, with 94% of roof heat loss attributable to the roof type ‘Pitched Roof, Insulated on Ceiling’; 6

As noted in Appendix A, there are 126 instances where area and heat loss information is not recorded for doors, thus heat loss attributable to doors is under-reported in the sample.

49


100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Pitched Roof – Insulated on Ceiling

Pitched Roof – Insulated on Rafter

Room in Roof – Insulated on side

Flat Roof

Area

92.9%

2.2%

3.7%

1.1%

Heat Loss

94.0%

1.7%

2.6%

1.7%

Figure 25 Roof Type and Heat Loss profile

The profile of roof insulation across the sample as noted during dwelling assessments is illustrated in Figure 26 (below). Insulation thickness was recorded for 646 dwellings and 1,097 roofed areas in the sample. Only 27% of roofed areas meet or exceed current regulations (~300mm), approximately 7% of areas have less than 100mm of insulation present, while the insulation in a considerable proportion of areas is ‘Not Listed’. 30% 25% 20% 15% 10% 5% 0% 0mm Contribution 0.64%

25mm 50mm 75mm 100mm 150mm 200mm 250mm 0.36%

4.38%

1.55% 24.34% 11.67% 8.66%

>=300 mm

Not Listed

2.92% 27.16% 18.32%

Figure 26 Roof Insulation Profile

50


4.3.1.3.4 Walls Walls are the largest contributor to total fabric area and fabric heat loss, contributing 38% and 34% respectively. As illustrated in Figure 27 (below), several wall types are present in the sample; 70%

60%

50%

40%

30%

20%

10%

0% 300mm Cavity

300mm Filled Cavity

Concrete Solid 225mm 325mm Hollow Mass Solid Brick Solid Brick Block Concrete

Area

60.3%

8.5%

14.4%

2.3%

0.3%

Heat Loss

51.5%

4.4%

28.5%

2.7%

0.5%

Stone

Timber Frame

0.2%

8.4%

5.6%

0.6%

8.3%

3.5%

Figure 27 Wall Type and Heat Loss profile

Several items are noteworthy; •

That 60% of wall area and 51.5% of wall related heat loss is attributable to easily treatable 300mm Cavity construction indicates that significant reductions in wall related heat loss can be readily achieved.

A significant portion of wall related heat loss is attributable to concrete hollow block construction, which contributes 14% and 28% of total wall area and wall related heat loss respectively. An examination of the data reveals this construction type to be most prevalent in age bands E (1967 – 1977) and G (1983 – 1993), though some use is noted in band I (2000 – 2004) also, possibly the result of dwellings being extended.

The proportion of area and heat loss attributable to single leaf, ‘hard to treat’ wall types is small.

51


4.3.1.3.5 Windows Windows contribute only 7.3% planar area for the entire sample, yet account for 19% of total planar heat loss, making them the second worst performing planar element, per unit area. As Figure 28 (below) illustrates, several glazing types are present in the sample, however Double Glazed Air and Argon filled units predominate. Interestingly, 10% of all window related heat loss is attributable to single-glazed units, the majority of which are found in age bands G (1983 â&#x20AC;&#x201C; 1993) and H (1994 â&#x20AC;&#x201C; 1999). 80% 70% 60% 50% 40% 30% 20% 10% 0% Single-glazed

Double-glazed, air filled

Double-glazed, argon filled

Triple-glazed, air filled

Area

6.20%

75.46%

18.10%

0.23%

Heat Loss

10.38%

73.27%

16.35%

0.22%

Figure 28 Window Type and Heat Loss profile

Window frames must be considered when assessing window related heat loss, with Figure 29 (below) illustrating that over 6% of frames are of thermally inferior metal construction;

52


100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

% Contribution

Wood/PVC

Metal no thermal Break

93.28%

4.75%

Metal 4mm Metal 12mm Metal 20mm thermal thermal thermal Break Break Break 1.87%

0.00%

0.10%

Figure 29 Frame Type profile

4.3.1.3.6 U-Value comparison Having formed a view of the make-up of various planar elements and their contribution to heat loss across the sample, it is useful to determine how the thermal performance of WCC planar elements compares with those at county and national level. Average thermal transmittance values for planar elements in WCC dwellings are obtained from assessed data. Values representing Ireland (286,793 dwellings) and Co. Wicklow (8,465 dwellings) are derived from the NBERRT.

53


3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

Avg. Wall U-value

Avg. Roof U-value

Avg. Floor U-value

Avg. Window U-value

Avg. Door U-value

Ireland

0.65

0.35

0.44

2.77

2.53

Co. Wicklow

0.76

0.44

0.47

2.80

2.41

WCC

0.90

0.41

0.54

2.80

2.87

2

Figure 30 Elemental U-value comparisons (W/m K)

Several items are noteworthy in Figure 30 (above); •

The average WCC wall U-value is significantly higher than the county and national average.

The average WCC roof U-value outperforms the county average but is considerably higher than the national average.

The average WCC floor U-value is higher than both county and national averages.

Average window U-values for WCC and Co. Wicklow dwellings match, with negligible difference to the national average.

The average WCC door U-value is higher than both county and national averages.

54


4.3.1.4 Thermal Bridging Heat Loss To examine heat loss through planar elements in isolation ignores heat loss through thermal bridges which, as noted earlier, contributes 12% to total heat loss and 16% to fabric heat loss across the sample, a contribution larger than heat loss through roofs and doors combined. As shown in Figure 31 (below), the contribution of thermal bridging to fabric heat loss increases over time; a reflection of increasing dwelling size and also of a decreasing contribution of planar heat loss to fabric heat loss as a result of increasing insulation standards. Note how the contribution to fabric heat loss for newer dwellings reaches over 23%, highlighting it as a significant issue to be addressed; 25%

20%

15%

10%

5%

0%

% Contribution

A-D ('00E ('67-'77) F ('78-'82) '66) 9.7%

10.0%

15.4%

G ('83'93)

H ('94'99)

I ('00-'04)

J ('05+)

17.4%

19.3%

19.6%

23.2%

Figure 31 Thermal Bridging contribution to Fabric Heat Loss

A thermal bridging factor of Y=0.157 was recorded for all dwellings in the sample. The average thermal bridging factor as derived from the NBERRT for dwellings both in Ireland (286,793 dwellings) and County Wicklow (8,465 dwellings) is Y=0.147, with values as low as Y=0.001 noted.

7

A discussion of Y-Factors is presented in Appendix B.

55


4.3.1.5 Heat Loss Parameter As noted previously, total dwelling heat loss (referred to in DEAP as the ‘Heat Loss Coefficient’) is the combination of ventilation, planar and thermal bridging heat losses. To facilitate comparison across dwellings of different types and sizes, this can be normalised per unit of floor area. This quantity (the ‘Heat Loss Parameter’) is an indicator of the efficacy of the thermal envelope. An analysis of the data reveals that the Heat Loss Parameter decreases for newer dwellings, with a value of 5.5 W/K/m2 for dwellings in age bands A-D (1900 - 1966), and 2.4 W/K/m2 for dwellings in age band I (2005+). Average Heat Loss Parameter values per dwelling type in the sample are illustrated in Figure 32 (below); 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 W/K/m²

Detached

End of terrace

Semi-detached

Mid-terrace

Apartment

3.47

3.05

2.67

2.49

2.49

Figure 32 Average Heat Loss Parameter per dwelling type

Several trends are noticeable; •

Having a total planar area 24% greater than any other dwelling type, detached units have the largest heat loss parameter.

Larger ventilation heat loss, a slightly greater average planar area and a greater total area of concrete hollow block construction are contributing factors in end of terrace units performing worse than semi-detached units.

Apartments and mid-terrace dwellings have the lowest heat loss parameter, possibly on account of their small planar area and low ventilation heat loss. 56


4.3.1.6 Net Space Heat Demand The Heat Loss Parameter provides the ability to compare the rate of heat loss per unit floor area across dwelling types. An aim of this study is to determine reductions in energy consumption achievable through the implementation of various thermal envelope retrofit strategies, assuming all other energy related variables, including heating system and fuel type to remain unchanged. Net Space Heat Demand (NSHD) is the quantity which best relates rates of heat loss with rates of energy consumption, and is defined as â&#x20AC;&#x153;the heat to be delivered to the heated space by an ideal heating system to maintain the set-point temperature during a given period of timeâ&#x20AC;? (SEAI a, 2008, p. 26). NSHD is derived by balancing total envelope heat loss with standardised internal and solar gains for an assumed internal-external temperature difference. The heat capacity (thermal mass) of the dwelling is accounted for. Notably, NSHD is independent of heating system type and fuel type, thus, monitoring changes in NSHD as a result of thermal envelope retrofit interventions allows the truest theoretical impact of thermal envelope related measures on energy consumption to be determined, ceteris paribus. 140 120 100 80 60 40 20 0

kWh/m²/yr

Detached

End of terrace

Semidetached

Mid-terrace

Apartment

120

100

89

76

76

Figure 33 Average Net Space Heat Demand per dwelling type

An anticipated, and as highlighted in Figure 33 (above), average NSHD per dwelling type reflects trends in Heat Loss Parameter.

57


4.3.2

Key Findings

Section 4.2 illustrated how the energy performance of WCC dwellings in terms of overall energy consumption, CO2 emissions and hence BER, is below that of average dwellings in Co. Wicklow and Ireland. A thorough disaggregation of information provided by Wicklow County Council and as collated by the model has provided several reasons for this poor performance; •

Ventilation rates are prime facie considerably higher than for average Co. Wicklow and Irish dwellings; this may be related to a higher average number of chimneys per dwelling in WCC and lower proportion of timber framed units in WCC.

Significant deficiencies were noted in attic insulation levels, despite the roof type profile suggesting a high proportion of roofed areas capable of accommodating 300mm of insulation.

The majority of windows across the sample are relatively poorly performing double-glazed units.

Average U-values for critical planar elements such as walls and floors fare poorly in comparison with average values for dwellings in Ireland and Co. Wicklow

The corollary of the above is that there exists significant scope for improvement in the efficacy of the thermal envelope of dwellings included in the sample. Certainly the significant degree of uniformity in roof and floor types suggests that any suitable retrofit interventions may have widespread applicability, while large reductions in heat loss through walls should be readily achievable given the high proportion of cavity construction in the sample. It is noted that differences in the relative proportions of dwelling types and their age distribution in the sample analysed in this study and that present in the NBERRT may play a role in performances differences noted here, though this is not explored further in this study. There now follows an analysis of retrofit interventions being recommended to Wicklow County Council by energy assessors.

58


4.4 Recommended Interventions Analysis It is clear from sections 4.2 and 4.3 that the thermal envelope in WCC dwellings is poorly performing, with the output of the model identifying principle areas of heat loss. When performing a dwelling assessment and recommending interventions to be undertaken, assessors are operating in a vacuum, unaware of the overall energy performance of WCC’s stock. It is likely, therefore, that although the interventions they recommend will address the energy consumption of the dwelling in question, large areas of heat loss at the stock level may remain unaddressed. Gaining an understanding of the suitability of the interventions being recommended to WCC by assessors in mitigating heat loss at the stock level is a key research question. An analysis of such interventions serves not only to highlight the emphasis being placed on the thermal envelope, but also facilitates the creation of a ‘business as usual’ scenario which can be used to model the impact of thermal envelope related interventions on heat loss across the sample. 4.4.1

Sample Creation

‘Energy Efficiency’ reports containing assessors recommended retrofit interventions were not available to the author for every dwelling included in this study, however, a random sample of reports representing 10% of dwellings below the C1 energy rating (68 in total) was compiled for analysis. This sample; •

Includes 10% of dwellings from each band below C1 (i.e. C2 – G)

Includes dwellings of all types included in the sample (Detached, Semi-detached, etc.)

Covers a broad spectrum of assessors

4.4.2

Sample Analysis

In total, 312 individual retrofit interventions were contained in this sample, which can be categorised as follows; Type Sample Interventions Space and Water Replacement boiler Heating Installation of time and temperature controls Installation of thermostatic valves Thermal Wall Insulation Envelope Replacement Windows Increase Attic Insulation Lighting Installation of low energy bulbs Renewable Technology (RET)

Installation of DHW systems

Table 11 Sample Recommended Interventions

59


The breakdown of interventions is shown in Figure 34 (below); 160 140 120 100 80 60 40 20 0

Space and Water Heating

Thermal Envelope

Lighting

RET

143

120

39

10

Total

Figure 34 Breakdown of recommended interventions

As would be expected, an emphasis is placed on heating (both space and water) and thermal envelope related interventions, with heating related measures dominant in all but the E2 & C2 energy bands, as shown in Figure 35 (below); 30 25 20 15 10 5 0

C2

C3

D1

D2

E1

E2

F

G

Space and Water Heating

4

17

27

28

18

12

14

23

Thermal Envelope

6

12

25

18

14

14

11

20

Lighting

2

4

12

6

5

2

3

5

2

3

RET

3

2

Figure 35 Recommended Interventions per BER

60


4.4.2.1 Thermal Envelope Interventions A disaggregation of thermal envelope related interventions per BER reveals the following;

Attic Doors Floor Walls - Cavity Walls - External Walls - Internal Walls - Not Specified Windows Ventilation Total

C2 5

C3 6

D1 11

D2 7

E1 8

1

2 1

4 1

1

3

3 1 2 3

5

3 2

12

5 25

1 18

14

E2 5

F 5

G 6 2

1

3 1 1 3 3 1 20

1

6

1 1 3 2 1 14

1 3 1 11

Total 53 2 1 15 5 8 22 6 8 120

Table 12 Recommended Thermal Envelope Interventions per BER

There are several key items to be noted; •

Attic insulation is the most frequently recommended intervention for all energy bands, perhaps reflective of its low cost and ease of installation.

Replacement doors are infrequently considered, with the only instances occurring in the lowest energy band.

Interventions aimed at improving the thermal performance of floors are least frequently included, and appear at a low energy band (E2), potentially reflecting their costly and disruptive nature.

Cavity fill insulation is the most frequently cited approach to reducing heat loss through walled areas. In a significant number of cases, a target U-value is specified, with no insulation strategy proposed.

The replacement of Windows is considered only at lower energy bands.

Ventilation related interventions primarily refer to draught-stripping and the blocking of disused chimneys, something perhaps indicative of low implementation costs.

4.4.3

Payback and Energy reductions

Where provided in ‘Energy Efficiency’ reports, the data reveals that heating related interventions often have superior payback times and offer larger primary energy reductions than thermal envelope related interventions, possibly due to the significant efficiency increases for boilers and the switching of fuel types from coal to gas or oil;

61


Average Annual energy saving (kWh/yr)

Average Cost (â&#x201A;Ź)

Average Payback (years)

2,917 (112 interventions)

1,977 (44 interventions)

23.1 (44 interventions

Space and Water 4,474 (112 Heating interventions)

1,186 (55 interventions)

9.35 (55 interventions)

Thermal Envelope

Table 13 Average energy savings, costs and payback times for recommended interventions

4.4.4

Key Findings

In light of the analysis in sections 4.2 and 4.3 on heat loss across the sample of dwellings, this section has highlighted several noteworthy points. Firstly, a fundamental tenet of the fabric first approach â&#x20AC;&#x201C; that insulation must be continuous around the thermal envelope â&#x20AC;&#x201C; is not being obeyed. The evidence analysed suggests that no assessor has recommended interventions addressing heat loss through every planar element in any dwelling in any energy band. However, this is to be expected when assessors are operating in a paradigm where the aim is to achieve a particular energy rating, as opposed ensuring the thermal envelope is optimised. Secondly, significant areas of heat loss remain unaddressed. Heat loss through floors accounts for 14% of fabric heat loss, yet measures to combat it are listed only once, and in that instance, no target U-value is specified. Windows contribute 19% of total fabric heat loss, yet their replacement or upgrade is considered only in lower energy bands, perhaps in an effort to replace single glazed units. Thirdly, when the sample of interventions is reviewed with a knowledge of comparative planar element U-value performance (section 4.3.1.3.6), it is clear that recommended interventions are somewhat focussed on elements where WCC performance is already comparatively good (roof), are ignored where performance is comparatively bad (floors) and in the most significant case where performance is particularly poor (walls), internal insulation is proposed more frequently than external insulation, an arguably more effective solution in light of its lower condensation risk and more effective treatment of thermal bridges.

62


Section 5. Scenario Analysis Scenarios are used to demonstrate the effects on overall heat loss, energy consumption and CO2 emissions of upgrading the thermal envelope to each of the following standards; 1. Better Energy Homes (BEH): this scenario assumes the thermal envelope of all dwellings to be upgraded using only measures funded under the BEH scheme (SEAI c, 2011). 2. Part L: this scenario assumes the thermal envelope of all dwellings to be upgraded to the standard defined in the latest iteration of the Irish Building Regulations (DECLG, 2011). 3. Wicklow County Council (WCC): this scenario assumes the thermal envelope of all dwellings to be upgraded using a composite of thermal envelope related interventions noted in section 4.4.2 4. EnerPHit: this scenario assumes the thermal envelope of all dwellings to be upgraded as defined in Feist (2010).

5.1 Scenario Definition Limiting values for ventilation rates, the thermal transmittance of planar elements of the thermal envelope and thermal bridging factors for each of these scenarios is discussed below. 5.1.1

Ventilation

Limiting factors for air-tightness for each of the standards considered are presented below;

Air Change Rate (achadj)8 No. Chimneys No. Flues

% Draught-stripping in place

BEH Scenario No Change No Change No Change

Part L Scenario 0.35

WCC Scenario 0.25

EnerPHit Scenario 0.03

Max 1

0

0

No Change

0

100%

100%

+1 where number of chimneys was >0 100%

100%

Table 14 Ventilation related limiting factors

The following assumptions are made; â&#x20AC;˘

All scenarios assume 100% draught-stripping measures in place

â&#x20AC;˘

The Part L scenario assumes max 1 chimney per dwelling.

8

Values for different standards have been standardised to air change rate (as required by DEAP) by dividing permeability values by 20, in accordance with (SEAI a, 2008, p. 13)

63


WCC scenario assumes not more than 1 chimney, which is converted to a flue for use with a solid fuel stove. This flue is not room sealed, so is considered to contribute to ventilation heat loss (SEAI a, 2008, p. 14).

EnerPHit assumes all chimneys are permanently blocked, all non room sealed flues are converted to be room sealed and solid fuel stoves with room sealed flues are installed in place of open fires. Room sealed flues are not considered to contribute to ventilation heat loss (ibid).

5.1.2

Element Thermal Transmittance

The thermal transmittance values assumed for each planar element in each scenario are presented in Table 15 below;

Walls

Roofs

Windows

Doors Floors

BEH Scenario Cavity U = 0.27 W/m2K External U ≤ 0.27 W/m2K Internal U ≤ 0.27 W/m2K Ceiling U = 0.16 W/m2K Rafter U = 0.20 W/m2K Flat U ≤ 0.27 W/m2K Not Specified

Not Specified Not Specified

Part L Scenario U ≤ 0.55 W/m2K U ≤ 0.35 W/m2K U ≤ 0.35 W/m2K U ≤ 0.16 W/m2K U ≤ 0.25 W/m2K U ≤ 0.25 W/m2K U ≤ 1.6 W/m2K Triple-glazed, air filled (low-E, εn = 0.15, hard coat), 16mm spacing U ≤ 1.6 W/m2K U ≤ 0.45 W/m2K

WCC Scenario U = 0.27 W/m2K U = 0.15 W/m2K U = 0.35 W/m2K U = 0.13 W/m2K Not Specified Not Specified U = 1.4 W/m2K Triple-glazed, argon filled (lowE, εn = 0.1, soft coat), 16mm spacing U = 1.3 W/m2K Not Specified

EnerPHit Scenario U ≤ 0.15 W/m2K U ≤ 0.15 W/m2K U ≤ 0.30 W/m2K U ≤ 0.12 W/m2K U ≤ 0.12 W/m2K U ≤ 0.12 W/m2K U ≤ 0.85 W/m2K Triple-glazed, argon filled (low-E, εn = 0.05, soft coat), user defined U-value U ≤ 0.8 W/m2K U ≤ 0.15 W/m2K

Table 15 Assumed values of thermal transmittance

The following assumptions are made; •

Window types have been selected on the basis of their match to the U-value required by the scenario. For EnerPHit, the use of a user-defined U-value is assumed, as no window type available in DEAP matches the required U-value.

All window frames are assumed to be of type ‘Wood/PVC’.

EnerPHit assumes all external insulation.

64


No preference for internal or external insulation is assumed for Part L or BEH scenarios, given they use identical U-values for each.

External insulation is assumed for all non-cavity walls in all scenarios except the WCC scenario where internal insulation is assumed to dominate, reflecting a preference for this method.

Where a target value for thermal transmittance is ‘Not Specified’, no interventions are modelled.

5.1.3

Thermal Bridging

As discussed in Appendix B, DEAP accounts for thermal bridging heat loss by applying a Y-Factor to the entire building envelope area. All assessments provided as input to this study assumed the default value of Y=0.15. A value of Y=0.08 can be used where evidence that bridges have been designed according to Accredited Construction Details have been used (SEAI a, 2008, p. 67); this value is assumed for all scenarios except EnerPHit to reflect that fact that thermal bridging is assumed to be addressed to a significant degree during retrofits. The criteria for thermal bridging is more stringent in the EnerPHit scenario, thus a custom Y-factor per dwelling type has been derived for this scenario9. The thermal bridging factors assumed in each scenario are presented in Table 16 (below);

Thermal Bridging Factor

BEH Y=0.08

Part L Y=0.08

WCC Y=0.08

EnerPHit Apartment Detached End Of Terrace Mid-Terrace Semi-Detached

(Y=0.0027) (Y=0.0033) (Y=0.0034) (Y=0.0032) (Y=0.0035)

Table 16 Assumed Thermal Bridging Factors

9

The derivation of these values is described in Appendix B.

65


5.2 Scenario Output The approach outlined above maintains the ability to model changes in primary energy consumption and CO2 emissions assuming heating systems to remain unchanged, at least in terms of fuel used. Given the limitations of the model used as outlined in section 3.3.4, and recognising its accuracy as noted in section 3.3.6, the following sections discuss the scenario output10. 5.2.1

Primary Energy Consumption

The Primary energy consumption profile for the four scenarios is as follows; 18,000,000 16,000,000 14,000,000 12,000,000 10,000,000 8,000,000 6,000,000 4,000,000 2,000,000 0 Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

448,880

448,880

448,880

448,880

448,880

Lighting (kWh/y)

1,191,308

1,191,308

1,191,308

1,191,308

1,191,308

Water Heating (kWh/y)

5,092,830

5,092,830

5,092,830

5,092,830

5,092,830

Space Heating (kWh/y)

9,438,747

5,746,795

5,229,395

4,135,441

1,253,174

BEH Scenario 39%

Part L Scenario 44%

WCC Scenario 56%

EnerPHit Scenario 87%

23%

26%

33%

50%

Pumps and Fans (kWh/y)

Reductions in Total Space Heating Consumption Reductions in Total Primary Energy Consumption

Figure 36 Reductions in Total Space Heating Consumption and Primary Energy Consumption

The BEH scenario is shown to achieve the lowest reductions in energy consumption, both overall and space heating related, with the Part L scenario only achieving only a further 3% reduction in total primary energy consumption over the BEH scenario.

10

Note that all reductions presented in this section are relative to the â&#x20AC;&#x2DC;No Changesâ&#x20AC;&#x2122; starting point for the model.

66


The WCC scenario fares better, reducing space heating consumption to such an extent that more energy is consumed heating water. Overall energy consumption is reduced 33%. As expected, the largest reductions are achieved in the EnerPHit scenario, with total space heating consumption reduced 87%, and total primary energy consumption reduced 50%.

5.2.2

Thermal Envelope Performance

5.2.2.1 Total Heat Loss Total heat loss from the thermal envelope can be disaggregated to ventilation heat loss, planar heat loss and thermal bridging heat loss as follows; 160,000 140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

Thermal Bridging Loss (W/mK)

17,963

9,580

9,580

9,580

400

Planar Heat Loss (W/K)

92,689

59,751

55,739

46,565

24,348

Ventilation Heat Loss (W/k)

35,885

35,313

31,571

27,566

23,691

Reductions in Ventilation Heat Loss Reductions in Planar Heat Loss Reductions in Thermal Bridging Heat Loss

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

2% 36% 47%

12% 40% 47%

23% 50% 47%

34% 74% 98%

Figure 37 Disaggregated reductions in thermal envelope heat loss

Reductions in ventilation heat loss are shown to vary widely from 2% in the BEH scenario to 34% in the EnerPHit scenario.

67


There is a significant difference in the reductions achievable in planar heat loss across the scenarios, with EnerPHit (74%) achieving more than double that of the BEH scenario (36%). Existing WCC interventions achieve a 50% reduction in planar heat loss. The most significant reductions of any type are reserved for thermal bridging heat loss in the EnerPHit scenario, which is all but eliminated.

5.2.2.2 Ventilation Heat Loss Average ventilation heat loss per dwelling for each scenario is as follows; 60.0 50.0 40.0 30.0 20.0 10.0 0.0

W/K

Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

50.0

49.2

44.0

38.4

33.0

Part L Scenario 12%

WCC EnerPHit Scenario Scenario 23% 34%

BEH Scenario Reductions in average 4% ventilation heat loss

Figure 38 Reductions in ventilation heat loss

The BEH scenario achieves negligible reductions, with Part L and WCC scenarios achieving 12% and 23% reductions respectively. EnerPHit achieves 34% reductions, with the inaccuracy inherent in this result arising from limitations of the model.

68


5.2.2.3 Planar Element Heat Loss The reductions in heat loss via building envelope elements are shown below; 100,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

Windows (W/K)

21,346

21,332

13,311

11,850

7,487

Walls (W/K)

37,833

12,385

21,101

12,209

6,881

Roofs (W/K)

12,765

5,289

5,320

4,628

3,837

Floors (W/K)

15,519

15,519

13,131

15,519

4,705

Doors (W/K)

5,216

5,216

2,873

2,346

1,443

BEH Scenario 0% 67% 59% 0% 0%

Part L Scenario 38% 44% 58% 15% 45%

WCC Scenario 44% 68% 64% 0% 55%

EnerPHit Scenario 65% 82% 70% 70% 72%

Windows Walls Roofs Floors Doors

Figure 39 Disaggregated reductions in planar heat loss

Several items are noteworthy; •

In the Part L scenario, floor heat loss is reduced 15%. It is difficult to see how this disruptive and costly work will be undertaken to achieve such a small reduction in heat loss. By comparison, the EnerPHit scenario achieves 70% reductions in floor heat loss.

Roof heat loss is reduced by a minimum of 58%.

The reduction in heat loss through walls is significantly lower in the Part L scenario as a result of the poor target U-values.

65% reductions in heat loss through windows are achieved in the EnerPHit scenario.

The significant reductions in planar heat loss would mean the proportion of fabric related heat loss attributable to thermal bridging would increase significantly were it not treated.

69


5.2.2.4 Thermal Bridging heat loss Reductions in thermal bridging heat loss are outlined below; 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0

Thermal Bridging Heat Loss (W/mK)

Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

17,963

9,580

9580

9580

400

WCC Scenario 47%

EnerPHit Scenario 98%

Reductions in Thermal Bridging Heat Loss

BEH Part L Scenario Scenario 47% 47%

Figure 40 Reductions in Thermal Bridging heat loss

The reductions in heat loss achieved under the EnerPHit scenario mean that less than 1 W/mK of heat loss per dwelling in the sample is attributable to thermal bridging, compared with 13.3 W/mK per dwelling in the other scenarios.

70


5.2.2.5 Heat Loss Parameter The average Heat Loss Parameter under each of the scenarios is highlighted in Figure 41 (below); 3 2.5 2 1.5 1 0.5 0

W/K/sqm

Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

2.7

1.94

1.8

1.55

0.89

Part L Scenario 33%

WCC Scenario 43%

Reductions in Heat Loss Parameter

BEH Scenario 28%

EnerPHit Scenario 67%

Figure 41 Reductions in Heat Loss Parameter for each scenario

Overall, there is little to differentiate the BEH and Part L scenarios. Although more significant reductions are achieved in the WCC scenario, the EnerPHit scenario achieves a further 24% in reductions, yielding a total reduction of 67%.

71


5.2.2.6 Net Space Heat Demand As noted in section 4.3.1.6, reductions in NSHD provide an indication in terms of energy consumption of the efficacy of the thermal envelope upgrade. Average values of NSHD across the sample under the 4 scenarios are presented in Figure 42 (below): 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 0

WCC Scenario

EnerPHit Scenario

Total Net Space Heat Demand 4,813,454 2,869,843 2,609,215 2,024,773 (kWh/y)

492,737

Assessed

Reductions in Net Space Heat Demand

BEH Scenario

Part L Scenario

BEH Part L WCC EnerPHit Scenario Scenario Scenario Scenario 40% 46% 58% 90%

Figure 42 Reductions in NSHD for each scenario

A similar trend as for all other modelled quantities is noted, with BEH and Part L achieving similar reductions. WCC scenario performs better, achieving 58% reductions. 90% reductions are achievable under the EnerPHit scenario.

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5.2.3

CO2 Emissions Reductions

Total CO2 emissions for the sample under each of the scenarios are as follows; 4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0

Total Emissions (kg/y)

Assessed

BEH Scenario

Part L Scenario

WCC Scenario

EnerPHit Scenario

4,149,031

3,154,299

3,018,161

2,726,919

1,969,388

BEH Scenario 24%

Part L Scenario 27%

WCC Scenario 34%

EnerPHit Scenario 52%

Reductions in CO2 Emissions

Figure 43 Reductions in CO2 emissions in each scenario

CO2 emissions can be reduced by 24% through addressing heat loss in walls and roofs as per the BEH scenario. There is negligible improvement in reductions under the Part L scenario. The WWC scenario sees CO2 emissions reduce by over a third. The largest reductions are reserved for the EnerPHit scenario, which sees reductions of 52%.

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5.2.4

BER Profiles

To graphically illustrate the impact the fabric first approach can have on the energy performance of the sample, it is possible to generate a BER profile representative of each scenario, as presented in Figure 44 (below); 300 250 200 150 100 50 0

A3

B1

B2

Assessed

B3

C1

C2

C3

D1

D2

E1

E2

F

G

13

27

55

103

144

106

82

52

55

81

BEH

2

35

90

177

119

121

66

36

23

34

15

Part L

10

35

121

187

103

107

61

37

16

30

11

WCC

33

79

197

126

107

64

45

22

14

26

5

245

179

86

34

23

22

15

10

19

4

4

EnerPHit

2

75

Assessed Number of dwellings at or above C1

6%

BEH Scenario 18%

Part L Scenario 23%

WCC Scenario 43%

EnerPHit Scenario 82%

Figure 44 Assumed BER profiles for each scenario

The following points are noteworthy;

Several dwellings remain with G ratings, despite significant reductions in energy consumption under the EnerPHit scenario. Initial primary energy consumption for these units is shown to average 646 kWh/m2/yr.

Under the EnerPHit scenario, dwellings now achieve A ratings

As assessed, only 6% of dwellings met or exceeded the C1 rating. Depending on the scenario, between 18% and 82% of dwellings could do so.

As per DEHLG (a, 2010), funding will not be provided for any dwellings remaining at or below F rating post retrofit. This may be as many as 8 to 49 dwellings, depending on the scenario.

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5.2.5

Funding Achievable

As illustrated in Table 17 (below), government funding for retrofits is based on reductions in energy consumption per m2 floor area, with C1 remaining the target energy rating (DEHLG a, 2010, p. 2). Where the cost of implementing planned interventions exceeds the government funding available, WCC must meet the balance through internal funding. Primary Energy Consumption Reductions (kWh/m2/y) 0 – 50 50 -100 100 – 200 200 – 300 300 or more

Funding provided Not Funded 50% or €6,000, whichever is lesser 75% or €11,500, whichever is lesser 90% or €15,500, whichever is lesser 90% or €18,000, whichever is lesser

Table 17 Allocation of funding according to energy reductions achieved

The number of dwellings achieving reductions of the magnitude required for funding in each scenario is outlined in Figure 45 (below). Note that dwellings retaining an F or G BER following retrofit, and therefore are ineligible for funding, are included; 450 400 350 300 250 200 150 100 50 0

0 to 50 kWh/sqm/yr (unfunded)

50 to 100 kWh/sqm/yr

BEH Scecnario

395

Part L Scenario

328

WCC Scenario EnerPHit Scenario

100 to 200 kWh/sqm/yr

200 to 300 kWh/sqm/yr

300+ kWh/sqm/yr

196

98

20

9

236

117

26

11

124

355

196

30

13

3

159

423

98

35

Figure 45 Number of dwellings per funding bracket per scenario

75


Accounting only for dwellings that achieve a post-retrofit energy rating of E or higher, the amount of funding available under each scenario is outlined in Table 18 (below);

Maximum Funding available

BEH Part L WCC EnerPHit Scenario Scenario Scenario Scenario €2,330,500 €2,933,500 €4,689,000 €7,861,000

Table 18 Funding available for each scenario

From this analysis, it is clear that the work performed in a large proportion of dwellings under the BEH and Part L scenarios would fail to secure funding. Significantly more dwellings achieve 50 to 100 kWh/m2/yr and 100 to 200 kWh/m2/yr in the WCC scenario, so this would appear to be a better financial choice than either BEH or Part L. The EnerPHit scenario would secure the most funding, with 59% of dwellings achieving savings between 100 to 200 kWh/m2/yr, and 5% yielding over 300kWh/m2/yr.

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5.2.6

Key Findings

Accounting for the limitations inherent in the model noted previously in section 3.3, the reductions achieved for each modelled quantity in each scenario are as follows; Modelled Quantity Ventilation Heat Loss Planar Heat Loss Doors Floors Roofs Walls Windows Thermal Bridging Heat Loss Heat Loss Parameter Net Space Heat Demand Total Space Heating Consumption Total Primary Energy Consumption Total CO2 Emissions

BEH Scenario 2% 36% 0% 0% 59% 67% 0% 47% 28% 40% 39% 23% 24%

Part L Scenario 12% 40% 45% 15% 58% 44% 38% 47% 33% 46% 44% 26% 27%

WCC Scenario 23% 50% 55% 0% 64% 68% 44% 47% 43% 58% 56% 33% 34%

EnerPHit Scenario 34% 74% 72% 70% 70% 82% 65% 98% 67% 90% 87% 50% 52%

Table 19 Overview of reductions achieved for all scenarios

The BEH and Part L scenarios are shown to have broadly the same impact on key performance indicators such as total space heating consumption, total primary energy consumption and total CO2 emissions. This is interesting given the broader scope of the Part L scenario in terms of planar elements considered and the superior ventilation heat loss reductions achieved. Though the BEH scenario addresses only walls and roofs, the thermal transmittance values assumed are generally more stringent than the Part L scenario, resulting in planar heat loss reductions of only 4% less than Part L. The WCC scenario fares better, reducing ventilation heat loss by 23% and planar heat loss by 50%. These reductions are achieved despite failing to address floor heat loss, which in this scenario now accounts for 33% of remaining planar heat loss. Total primary energy consumption and total CO2 emissions are reduced 33% and 34% respectively in this scenario. However, these reductions are considerably less than the 50% reductions in total primary energy consumption and 52% reductions in CO2 emissions achieved in the EnerPHit scenario. The greatest reductions in all modelled quantities are achieved in this scenario; 34% reduction in ventilation heat loss, 74% reduction in planar heat loss, 98% reduction in thermal bridging heat loss and a 90% reduction in Net Space Heat Demand. 77


EnerPHit outperforms other scenarios in terms of funding achievable, and is capable of bringing 82% of dwellings to or above the C1 target energy rating, a proportion far in excess of the WCC scenario which manages to bring 43% to this standard or above. Finally, that a small number of dwellings retain F and G energy ratings following an EnerPHit thermal envelope upgrade serves to underline the poor performance of some dwellings in the sample.

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Section 6. Conclusions Using a custom-built model, dwelling energy assessment reports for 718 dwellings in Wicklow County Councilâ&#x20AC;&#x2122;s housing stock were analysed in order to profile energy consumption. A scenario analysis was performed to investigate the efficacy of various thermal envelope upgrade strategies. Objective 1: Profile dwelling energy performance This study considers headline indicators of dwelling energy performance to be overall energy consumption, CO2 emissions and BER rating. The data analysed shows the average dwelling in WCC to perform poorly in comparison with average dwellings in Co. Wicklow and Ireland on each front. A detailed analysis of heat loss across the sample highlighted significantly higher levels of ventilation heat loss in WCC dwellings compared with county and national averages. In terms of planar heat loss, walls were found to perform particularly poor in comparison with county and national averages. With 94% of the sample found to be below C1, the target energy rating for the NERP and government retrofitting work, it is clear a widespread retrofitting effort is required to bring WCC stock to standard. Objective 2: Analyse sample retrofit interventions A sample of 312 retrofit interventions recommended to WCC by external assessors was analysed. The majority of measures relate to space and water heating, and the thermal envelope. Thermal envelope related interventions were analysed further and shown not to address significant areas of heat loss through the thermal envelope and not to concentrate on planar elements whose performance is demonstrably poorer than county and national averages. Measures relating to space heating are shown to offer better CO2 reductions and payback times than thermal envelope related interventions. The economic attractiveness of heating related measures will encourage their uptake, particularly in a local authority where funding is scarce. However by implementing such measures at the expense of optimising the thermal envelope, WCC are committing to higher future energy consumption and CO2 emissions than would otherwise be the case, and are allowing health issues where they exist to persist. Objective 3: Model thermal envelope retrofit strategies WCCâ&#x20AC;&#x2122;s existing strategy of replacing boilers, upgrading heating systems and making piecemeal improvements to the thermal envelope is a valid approach and will yield results in terms of energy consumption and CO2 emissions reductions, but currently does not adequately address the sources of heat loss in the thermal envelope. Furthermore, health issues, where present, are allowed to 79


persist under this regime. 4 scenarios, each embracing the fabric first approach to differing degrees, and one a composite of existing WCC thermal envelope related interventions, are used to demonstrate the primacy of the fabric first approach in reducing energy consumption and CO2 emissions in the sample. Significant improvements in the energy performance of the stock are possible; •

Primary energy consumption reduced by between 23% and 50%

Total CO2 emissions reduced by between 24% and 52%

Between 18% and 82% of dwellings brought to the C1 standard or above

These reductions alone could make a significant contribution to WCC’s obligations regarding energy efficiency improvements under the NEEAP. Indeed these reductions could go some way to achieving the 90% reductions in CO2 emissions deemed possible in the residential sector, and are all the more impressive when it is considered that they are possible solely through addressing the thermal envelope. With space heating related energy consumption reduced by up to 87%, remaining heat demand could now be met with gas boilers of greatly reduced size, or through the use of renewable technologies. Questions remain over the practicalities of implementing the retrofits assumed here, particularly the EnerPHit scenario, which may require up-skilling of staff. Funding of between €2.3 million and €7.8 million could be secured depending on the scenario, however the financial viability of each scenario requires detailed analysis. Objective 4: Extrapolate stock-wide impacts of retrofits As noted in section 3.5, no suitable scaling factor could be determined to allow the reductions in energy consumption and CO2 emissions across the stock to be estimated. The determination of such a factor represents an area for further research.

80


6.1 Further Research Several areas suitable for further research have been identified: •

The determination of a suitable scaling factor to allow savings estimated in this study be extrapolated to the stock level would provide a more complete view of the savings achievable for any particular scenario.

To enhance the model to reflect how heating system upgrades could affect energy consumption and CO2 emissions across the sample would further validate the efficacy of the fabric first approach. The consideration of heat pumps here would be of interest.

The ‘Y-Factors’ assumed in during thermal bridging modelling in this research represent extremes of the scale; it would be a worthy exercise to determine suitable values for each dwelling type in WCC’s stock for use in further analysis.

A cost effectiveness study to demonstrate the financial viability or otherwise of the EnerPHit scenario in particular represents a worthy exercise.

81


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Wardell, G., & Shanks, K. (2005) Energy Performance Survey of Irish Housing. Dublin: City of Dublin Energy Management Agency. Watson, D., & Williams, J. (2003) Irish National Survey of Housing Quality 2001 - 2002. Available from: http://www.environ.ie/en/Publications/DevelopmentandHousing/Housing/FileDownLoad,2446,en.p df [Accessed July 20 2012] Wicklow County Council (WCC) (2008) List of Houses at 31st Dec 08. Wicklow County Council. Wicklow County Council (WCC) (a) (2011) BER Upgrade Database. Wicklow County Council. Wicklow County Council (WCC) (b) (2011) BER Provision of Services 220611. Wicklow County Council. Wicklow County Council (WCC) (c) (2011) BER Assessor List Issued 080711. Wicklow County Council. Wicklow County Council (WCC) (d) (2011) Application Form for BER Upgrade Works. Available from: http://www.wicklow.ie/apps/wicklowbeta/News/BER.aspx [Accessed July 20 2012]

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Appendix A – Data Quality Number of Units Overall, dwelling reports for 722 dwellings were provided as input to this study. A total of 4 dwellings were excluded as their input files were corrupt, or contained blank worksheets. The total number of units included in the analysis is 718. Dwelling Type 1 unit (‘Church Lane’) was assumed to be ‘detached’ in the absence of any other information. 16 units were assigned the dwelling type of ‘House’ during their assessment. Following consultation with other sources (such as the accompanying Energy Efficiency report, or Google Earth), these were assigned a dwelling type more consistent with others in the study. Data Consistency The following minor inaccuracies were noted, and were held consistent during the modelling of retrofit interventions; Doors: Information relating to heat loss through doors was not recorded for 126 dwellings. Floors: There are 24 instances where top floor apartments incorrectly have values of floor heat loss ascribed to them (SEAI a, 2008, p. 82). Roofs: There are 12 instances where ground floor apartments incorrectly have values of roof heat loss ascribed to them (SEAI a, 2008, p. 82). Windows: The calculation of heat loss through windows in DEAP factors in several variables. Firstly, based on the glazing type, a default U-value is assigned. For double and triple glazed units, this can vary depending on the inter-glazing spacing. The U-value is further altered based on frame type and the assumed use of curtains (SEAI a, 2008, p. 17). ''Roof' windows incur an additional factor when the adjusted U-value is being calculated. SEAI (a, 2008, p. 95) shows that the value of orientation used for roof windows can vary between 'North' and 'Horizontal' based on the pitch of the roof and the orientation of the window, thus all windows with a horizontal orientation are assumed to be 'roof windows', however it does not follow that all North facing windows will be roof windows (and this cannot be determined as roof pitch is not captured in the DEAP output files). Several factors introduce error in the modelled estimation of window related heat loss;

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Roof Windows: Horizontal units are recorded for only 28 units. All but 2 of these are listed as 'roof windows' and accordingly, the adjusted U-value used in the model and recorded in the DEAP assessment differ, introducing a small error in the glazing heat loss. 11 Kiladreenan Close (Row 601, Window 3) is an example of a Horizontal window that is not listed as a roof window. Hence as it stands, the adjusted U-value from DEAP output and in the model match. Roof windows or northerly orientation are recorded in 5 units. The Adjusted U-values in the model and DEAP files differ for each such window. Thus, without the inclusion of the roof factor in the model, the glazing heat loss for 33 units (4.6% of the sample) are slightly incorrect. User Defined U-values: A large discrepancy loss (circa 12%) is seen in planar heat loss for 17 Burnaby Lawns (row 54) as a result of user defined U-values being entered glazed units. The model cannot recognise user-defined U-values, and in this case, overestimates planar heat loss. Possible Assessor error, or DEAP version mismatch: See 43 Monastery Grove (row 189). The DEAP Assessment file clearly shows that both windows are assessed as being 'Double Glazed - Air Filled', with U-Values of 2.7 and adjusted U-Values of 2.6811. Both windows are Wood/PVC framed with the same frame factor, over-shading and glazing gap (>=16mm). Neither windows are roof windows. With areas of 3.54 and 4.37sq.m, the cumulative heat loss is expected to be 21.2 W/K, however the dwelling report indicates heat loss to be 19.30 W/K, which, prima facie, is incorrect. Creating windows such as described above in DEAP yields a heat loss of 19.30, though the adjusted U-Values for the windows are 2.44, not 2.68 as captured in the dwelling report. This introduces an error in the model, as it uses the seemingly incorrect 2.68 for the assessed adjusted U-value, and then 2.44 as the modelled one. It is not known how the dwelling report captures one adjusted U-Value yet presents a conflicting value of heat loss. Similarly, see 10 Bayview Close (row 17, window 3); here the adjusted U-value in the model matches that of DEAP, however is different to the adjusted U-value from the DEAP output file, hence a difference in the heat loss is evident. In both of these cases, assessor error is possible, or perhaps a different version of DEAP was used for the assessment than is assumed used for the model.

11

A U-value of 3.0 is required in DEAP to have an adjusted U-value of 2.68

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Appendix B – Thermal Bridging ‘Y-Factors’ With regards the inclusion of thermal bridging heat loss in DEAP calculations, SEAI (a, 2008, p. 67) notes the following; The quantity which describes the heat loss associated with a thermal bridge is its linear thermal transmittance, Ψ. This is a property of a thermal bridge and is the rate of heat flow per degree per unit length of bridge that is not accounted for in the U-values of the plane building elements containing the thermal bridge. The transmission heat loss coefficient associated with non-repeating thermal bridges is calculated as:

HTB = ∑(L*Ψ)

where L is the length of the thermal bridge over which Ψ applies.

If details of the thermal bridges are not known, use HTB = y ∑Aexp where Aexp is the total area of exposed elements, measured in m2 Y in the above formula represents a multiplier which can have 3 values; 1. Y=0.15 applies in all cases other than 2 or 3 below 2. Y=0.08

applies

where construction details conform with Acceptable

Construction Details 3. Y=0.11 applies where a dwelling has been built under to 2005 Building Regulations As noted in section 5.1.3, all assessors assumed the default value of Y=0.15 during the dwelling assessments for dwellings in the sample. The BEH, Part L and WCC scenarios assume a value of Y=0.08 to reflect an assumed degree of attention towards reducing thermal bridging during retrofits.

The EnerPHit scenario requires more stringent treatment. A stipulation of this standard is that no thermal bridge will have a thermal transmittance greater than Ψ = 0.01 W/mK (Feist, 2010, p. 8). What is required is to deduce a suitable Y-Factor for use in the model for the EnerPHit scenario.

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Assumptions; •

All dwellings are 2 storey, except Apartments which are considered 1 storey.

All Dwelling footprints are square in nature

External insulation is used, thus intermediate floor thermal bridge is removed.

Step 1: Estimate length of ground floor and eaves thermal bridges: Dwelling Type

Apartment Detached End of terrace Mid-terrace Semi-detached

Avg. Assumed Assumed Assumed Floor length of Number Perimeter area side (m) of (m) 2 (m ) Exposed Sides 47.2 6.9 1 6.87 75.5 8.7 4 34.77 82.6 9.1 3 27.27 80.2 9.0 2 17.92 79.4 8.9 3 26.72

Multiplier for thermal bridge at eaves and ground floor 1 2 2 2 2

Assumed Average Bridge Length (m) 6.87 69.53 54.53 35.83 53.45

Step 2: Estimate length of Window related thermal bridges: Dwelling Type

Apartment Detached End of terrace Mid-terrace Semi-detached

Average Assumed Assumed Glazing number Window Area of area (m2) Windows (m2) 8.3 12.7 14.5 13.7 11.1

3 8 7 4 7

Assumed side length for Window (m)

Assumed Average Bridge Length (m)

1.7 1.3 1.4 1.9 1.3

6.6 5.0 5.8 7.4 5.0

2.8 1.6 2.1 3.4 1.6

Step 3: Estimate length of Door related thermal bridges: Dwelling Type

Apartment Detached End of terrace Mid-terrace Semi-detached

Average Door area (m2) 1.91 2.72 1.99 2.40 3.03

Assumed number of Doors 1 2 2 2 2

Assumed Door Area (m2) 1.91 1.36 1.00 1.20 1.51

Assumed Average Bridge Length (m) 5.82 4.72 3.99 4.40 5.03

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Step 4: Determine Y Factor:

Apartment Detached End Of Terrace Mid-Terrace Semi-Detached

Assumed Total Bridge Length (m) 19.32 79.30 64.28 47.64 63.52

Ψ (W/mK) 0.01 0.01 0.01 0.01 0.01

Heat flow (W/K) 0.193245 0.792973 0.642828 0.476377 0.63516

Avg. Planar Element Area (m2) 97.58216 243.2564 186.1614 148.8264 184.0234

Y Factor (W/K/m2) 0.00198 0.00326 0.003453 0.003201 0.003452

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Assessing the potential for reductions in Irish Local Authority residential energy consumption