Carbon Footprint Study 7001.5 MArch Rakesh Kumar Morar
Introduction This study will focus on the key design principles and the environmental strategies that will be implemented in order to reduce the amount of electricity and fossil fuels needed to operate in the building design I have proposed on a yearly basis. In order to achieve the energy requirements of Passivhaus the following performance parameters will be taken into consideration and incorporated into my scheme. It is important to take consideration of the amount of energy a building consumes during its lifespan, as this has a huge impact on our environment. Therefore, the calculations used in this study will be used as an accurate guideline rather than inaccurate estimation. In order to reduce the carbon footprint for my proposal, locally sourced materials and renewable energy will be considered to align with energy benchmarks. Therefore data from Camden Passivhaus will be used as a guideline in order to help me forecast annual energy consumption figures for my proposed design. The term Passivhaus refers to an advanced low energy construction standard for buildings, which have excellent comfort conditions in both winter and summer. They typically achieve a heating saving of 90% compared to existing housing. 1 Passivhaus buildings are easy to live in and require little maintenance, but they do have some important features, which will be explained later on in the report. The features are simple to operate, but a full understanding will help you get the lowest energy consumption and best comfort. A Passivhaus building requires very little energy for heating or cooling, whilst providing a high level of comfort for the occupants. Passivhaus was developed in the 1990s by Dr Wolfgang Feist, who was concerned that buildings consumed much more energy when built than was predicted at the design stage. Attention to detail, rigorous design and construction and an exacting certification process ensure that what is designed is built, and what is built performs as it was designed. This is achieved primarily through a fabric first approach, meaning high levels of thermal insulation, high levels of airtightness and the use of whole house Mechanical Ventilation with Heat Recovery (MVHR). The thermal insulation requirements of Passivhaus demand that roof, wall and floor Uâ€“values are equal to or less than 0.15 W/m2.K.2
http://www.bere.co.uk (Ranulf Road User Guide) http://www.kingspaninsulation.co.uk (Passivhaus-Buildings-Case-Studies-March-2012.pdf)
Case Study: Camden Passivhaus, London
Project Description This project is an 118m2 single-family house split over two floors. The primary objective of this project was to achieve a comfortable home for a young family, whilst minimising energy consumption. It contains two wild flower meadow roofs and a south facing garden enclosed by an ivy fence to increase local biodiversity (Fig.1). Healthy air and water quality is prioritised by using non-toxic materials; heat recovery ventilation and water filtration for drinking and bathing. Mains water use is supplemented by an underground water-harvesting tank providing water for irrigation.4 It is Londonâ€™s first certified Passivhaus dwelling, Camden Passivhaus incorporates heat recovery ventilation (HRV, or MVHR), extremely good insulation and air-tightness, and high performance glazing to create comfortable and healthy conditions, and minimise energy requirements.5 House Area: 118m2 Total floor area: 100m2
Fig.1. South facing roof garden 3
http://www.bere.co.uk http://www.bere.co.uk (Camden Dissemination (BSRIA) SML_0.pdf) 5 http://www.bere.co.uk (Camden Dissemination (BSRIA) SML_0.pdf) 4
The following data for Camden http://www.lowenergybuildings.org.uk.
Design Strategies Planned occupancy - 2-3 people Space heating strategy - All heating is supplied through the ventilation system (with towel radiators in the bathrooms for additional comfort). The heat for the air is supplied by the solar water tank/ a small gas-condensing boiler. Water heating strategy - Solar hot water (with gas condensing boiler top up). Fuel strategy - Mains Gas Renewable energy strategy - 3sqm of solar thermal collectors Passive solar strategy - The window proportions and the use of passive solar gains have been optimised using PHPP. Space cooling strategy - Natural cross and stack ventilation for summer cooling. External louvres with solar control for summer shading. Daylighting strategy - The living, kitchen and dining areas are located on the first floor to minimise the need for artificial lighting. Ventilation strategy - Mechanical heat recovery ventilation (winter) Natural ventilation with extract only ventilation in the bathroom and WC (summer) Airlightness strategy - OSB with taped joints and an intello membrane Strategy for minimizing thermal bridges - Thermal bridge-free construction throughout and all junctions have been modelled in Heat2 and the results fed into the PHPP. Modeling strategy - Every junction of the building was optimised using a thermal modelling programme Heat2 and then fed back into the Passivhaus Planning Package. Insulation strategy - Despite being located in one of the milder areas of the UK, the house on Ranulf Road required high levels of insulation due to overshadowing from neighboring buildings. The levels of insulation:400mm wood fibre insulation above the concrete slab, 280mm mineral wool +100mmwood fibre insulation in the external walls, 280mm PUR + 120mm mineral wool insulation in the flat roof and 380mm mineral wool insulation in the sloping roof.
Building Services Space heating - All heating is supplied through the ventilation system (with towel radiators in the bathrooms for additional comfort). The heat for the air is supplied by the solar water tank/ a small gas-condensing boiler. Hot water - 3 square meters of solar thermal provide up to 50% of the domestic hot water, the rest is topped up with a gas-condensing boiler. Ventilation - The Paul thermos 200 DC has been installed in Ranulf Road. The ventilation unit achieves a heat recovery efficiency of 90.1% whilst the electric efficiency is of 0.36 Wh/m3.
Controls - Room thermostat in the living room, if the room temperature drops below 20 degrees, the 2 towel radiators will automatically switch on. The master bedroom has a boost switch for increased user comfort. Cooking - Electric induction hob and oven. Lighting - Low energy LED and fluorescent lighting throughout the building. Appliances - Every appliance was rigorously chosen and had to comply with the high levels of efficiency set in PHPP. Where possible the appliances are A++ rated. Renewable energy generation system - A 3sqm solar thermal panel is installed on the main flat green roof. Strategy for minimising bridges - All junction details are designed to prevent thermal bridges and the results form part of the Passivhaus Planning Package (PHPP) energy calculations.
Building Construction Volume - 256m³ Thermal fabric area - 388 m² Roof description - Ranulf Road has a flat roof with massive wood panels, 280mm PUR and 120mm mineral wool insulation and a wild flower meadow roof. The building has another wild flower meadow on the sloping roof at the rear of the property, with 380mm mineral wool insulation in a timber frame construction. Roof U-value - 0.11 W/m² K Walls description - The lower retaining external wall build-up (from the outside) is 200mm thick Caltite concrete, 240mm timber studs with mineral wool between the studs, a 15mm OSB board and the air tightness membrane and finally a 100mm service zone filled wood fibre insulation. The upper external wall build-up (from the outside) is Austrian larch cladding on battens, building paper and 15mm thick fermacell panels fixed to 280mm timber studs with mineral wool between the studs, a 15mm OSB board and air tightness membrane and again an insulated 100mm service zone. Wall U-value - 0.11 W/m² K Floor description - Before the timber frame was installed the insitu concrete floor slab and retaining walls were cast. The timber frame ground floor build-up includes 2 x 140mm timber beams with wood fibre insulation between. The air tightness membrane is laid over these beams and a final 100mm deep service void is created with 100mm timber beams with wood fibre insulation between. The floor finish is 16mm engineered oak floorboards. Floor U-value - 0.10 W/m² K Glazed doors description - The entrance door is a triple glazed Passivhaus door. Glazed doors U-value - 0.81 W/m² K installed Window description - The windows are high performing triple glazed windows from Germany with a warm edge spacer (psi 0.039W/mK). Window U-value - 0.76 W/m² K Window energy transmittance (G-value) - 50 % Window light transmittance - 71%
Fig.2 Ground and first floor layouts6
Fig.2 shows ground and first floor plan layouts of the prefabricated timber frame highlighted in yellow. These factors mentioned above have made Camden Passivhaus a ‘Quality Approved Passive House’. The planning of this building meets the criteria for Passive House set up by the PHI (Passive House Institute). The Certificate mentions the following important information7…
The building features excellent complete thermal insulation and first grade connection details with respect to building physics. Summertime heat protection has been considered. The heating demand is limited to... 15 kWh per m2 living area and year or a heating load of max 10 W/m 2 The building shell features excellent air tightness, proven in accordance to ISO 9972, which guarantees the building to be free of draughts and reduces energy demands. The air change rate of the building shell at 50 Pascal pressure difference is limited to... 0,6 ach, which respect to building volume The building features a controlled ventilation system with high-class filters, highly efficient heat recovery and low electric power consumption. Thus, excellent air quality is achieved in combination with low energy consumption. The primary energy demand for standard use of heating, domestic hot water, ventilation and all other electric appliances sums up to less than 120 Kwh per m2 living area and year
http://www.bere.co.uk (Camden Dissemination (BSRIA) SML_0.pdf) http://www.lowenergybuildings.org.uk/viewproject.php?id=207#strategies
In order to conduct what I have researched and gathered from the precedential study, I will now go and implement it into my proposal. Using Camden Passivhaus as a guideline I will be to get near enough accurate readings as possible by using the following strategic approach. Environmental & Strategic approach In order for me to achieve Passive House design I will have to employ the following principles into my proposal… 1. 2. 3. 4. 5. 6. 7.
Super-insulate Eliminate thermal bridges Minimising thermal bypass Build airtight Ventilate with energy recovery Use Passivhaus certified doors and windows Optimise solar and heat gains
As each dwelling will be a purpose built Passivhaus structure, the terrace houses will include several notable features…
South–facing orientation of large living area glazing, allows the houses to be primarily heated naturally via solar gain. Each house features a double storey, ground floor consisting an open-plan kitchen living area and dining room. First floor (mezzanine) is a bedroom with an en suite, making the most of the limited available space inside the dwelling.
Design Targets Annual space heating
Whole house heat loss
63.6 W/K (PHPP)
<0.6 ACH at 50Pa
Flat roof 0.067 W/m2K Sloping roof 0.116 W/m2K terrace 0.139 W/m2K
Lower 0.125 W/m2K Upper 0.116 W/m2K
U-value: Ground Floor
MVHR: electrical efficiency
MVHR: heat exchanger efficiency
Table 1: Design Targets
In order for me to achieve Passivhaus requirements, I will use the following design targets in Table 1. The statistics are from Camden Passivhaus, and these design targets will be set and be used in order to see if each of my dwellings meets the Passivhaus requirements. To reach these standards, I will now go on to look at each strategy process in order to achieve the benchmark.
Construction & Material Each dwelling will be constructed via prefabricated timber frame as shown in Fig.3, with the ground floor set within a concrete retaining wall, supporting each side of the dwelling. The use of prefabricated systems reduces construction times and minimise waste.
Fig3. Ground and first floor prefabricated time construction
The wall will be timber framed and cladded in Austrian larch shown in Fig.4. The wooden cladding will give the dwelling a sense of a welcoming homely feel, due to its naturally warm colour, perfect for dementia occupants. One of my key aspects was to give the resident a place where they call home but also a place where they will feel safe and secure. Austrian cladding is far more superior to brick, steel and concrete, helping to keep buildings cool in summer and reduce heating costs in winter. It is naturally resistant to decay and insect attack
Fig4. Example Austrian larch cladding8
The dwelling will have two layers of insulation in the walls: 240-280mm of Rockwool Flexi between the timber studs, plus 100mm of natural wood fiber insulation inside the vapour control layer. It has 400mm of PIR insulation on the roof and 400mm wood fiber insulation on the floor slab, and an airtightness membrane stapled and taped throughout, designed to achieve an air permeability of 0.6 ACH (at 50Pa). Calculated U-values for the roof, floor and walls vary between 0.07 to 0.14 W/m2K. Insitu concrete floor slab will be used as the main foundation of the dwelling (See Fig5). Materials will be locally sourced, as this will reduce the emission of fossil fuels to transport the materials to the destination. The building will be cladded with use homegrown Scottish Larch 8
clad from a sustainable source within a 40 miles of the terrace’s location, again to minimise transport emissions. Building Fabric Passive House Planning Package (PHPP) will be used to iteratively refine the design, estimating energy use in many different spatial configurations. U-values required to meet the Passivhaus standard will be used to determine figures using this tool. Using PHPP will help me to be able to work out the optimum position of the dwelling and the best orientation for solar gains in the winter, but prevent overheating in the summer. As the client is subjected to dementia the key aspect is space, building height will be no more than double the surrounding context, keeping it within the boundaries of the neighborhood. Ground and first floor will have a height of 2.5m. The roof will have 400mm of insulation using high performing rigid foam with a thermal conductivity of 0.026 W/mK. This will maximize thermal performance while limiting the build-up, yielding a calculated U-value for the roof of 0.067 W/m2K. The ground floor will be insulated with 400mm of natural wood fibre insulation with a thermal conductivity of 0.035 W/mK, resulting in a calculated U-value of 0.103 W/m2K. To meet the stringent air tightness for leakage target will be less than 1m3/h/m2. In order to keep the leakage to minimum measures will include
Wet plaster coating to interior walls Floor slab carried across the top of the blockwork of the inner leaf of the wall. Careful consideration will be taken to airtightness detail around windows and door openings and junctions between floors, walls and roofs.
Buildings Services Ventilation, Heating and cooling Mechanical Ventilation with Heat Recovery (MVHR) is essential in an airtight building, to ensure there is fresh air to all the habitable rooms. It also removes moist stale air, reusing the heat to pre-heat the fresh air entering the building. Our system also includes a programmable Summer Bypass to maximise efficiency. 9 All heating will supply the dwelling through the ventilation system (with towel radiators in the bathrooms for additional comfort). The heat for the air is supplied via the solar water tank and also a small gas-condensing boiler. From the data gathered from Camden Passivhaus, a Paul thermos 200 DC will be installed in each dwelling. As the statics show from the precedent study, the ventilation unit achieves a heat recovery efficiency of 90.1% whilst the electric efficiency is of 0.36 Wh/m3. By using this method will result in minimising the carbon footprint. Mechanical ventilation will be used during the summer with heat recovery bypass. This will be controlled on the ground floor of the dwelling. Windows are opened for cooling during the day, but at night the windows can be closed. This is shown in Fig.5. The heating system is classic Passivhaus, heat requirement will be provided through the airflow of the ventilation system. In addition heat will be provided in the ventilation air, the boiler and solar combination will also supply heat. The Passivhaus standard requires thermal bridges to be less than 0.01 W/mK, and any bridges 9
unavoidably greater than 0.01 W/mK must be calculated and fed into PHPP to assess their impact on the overall energy use. HEAT2 will be used to operate and access thermal bridging.
Fig.5. MVHR - maximizing energy use and indoor comfort
Fig.6 Plan view of continuous airtight barrier
Lighting and shade Low energy LED and fluorescent lighting will be installed throughout the dwelling. LED bulbs are low in energy and have very high output. Very energy efficient reducing the cost of electricity used. This will mainly be used during the night period. During the day, light will be permitted from the large windows on the south side of the dwelling.
Low energy LED and fluorescent lighting10
Triple-glazed, Passivhaus-certified windows will be installed in each dwelling, locally sourced from Gloucestershire, UK. These windows have been designed to achieve U-values of 0.6 W/m2K (centre-pane) and 0.76 W/m2K overall (including frame). In additional large triple glazed windows will be used in order to provide light and potential for solar gains. Passivhaus certified glazed doors will also be installed which also provide excellent thermal performance. (See pictures below)
Triple-glazed, Passivhaus-certified windows 11
Passivhaus certified glazed doors12
The general layout of each dwelling is a traditional to modern day living standards in the UK. The ground floor consists of an open-plan kitchen, dining room and living room with a downstairs WC, while the first floor is a bedroom with its own en-suite. Large windows are essential to the passive solar heating strategy. As a result large windows are implemented on the south side of the dwelling so maximum daylight enters both the bedroom and living room on the ground floor. The living, kitchen and dining areas are located on the ground floor to minimize the need for artificial lighting. See Fig.7 & 8.
Fig.7 Ground and first floor plan study 10
http://media-cache-ec0.pinimg.com/236x/3b/bb/c7/3bbbc70dc153639a753bf13919b2270a.jpg http://apxe.eu/img/gallery/thumb_457.jpg 12 http://www.superhomes.org.uk/wp-content/uploads/2013/01/triple-glazing-seals.jpg 11
Fig.8 Sun study
Water In summer the sun shining on the solar panel on the roof heats almost all the water in the solar tank. In winter the panel can heat the bottom half of the tank and the boiler is used to top up the temperature. This means there is always hot water available in the tank even on a cloudy day. Rainwater harvesting will also be installed as part of each dwelling. Rainwater that is collected from the roof will be drained and stored in a tank under ground. This water will then be supplied to the en-suite, ground floor WC and washing area in the kitchen. See fig. 9.
Fig.9 Rainwater harvesting system
Energy generation A main gas pipeline will be fitted throughout the dwelling; solar thermal panels will be installed on the main roof as shown in Fig.5. Solar thermal collectors will also be installed as an addition to renewable energy source. Concluding benchmark figure To conclude on the report, using the figures from Table 1 from my precedent study and incorporating the same technologies and same energy generation systems that have been integrated into Camden Passivhaus, following this process will enable me to reach a Passive House dwelling to modern day living standards. Following all these methods to a high standard will enable me to achieve this figure or get relatively close to it to enable me to pass Passivhaus requirements.
Published on May 21, 2014