ROLE OF PASSIVE DESIGN TECHNIQUES IN IMPROVING THERMAL & DAYLIGHTING PERFORMANCE OF BUILDINGS

ROLE OF PASSIVE DESIGN TECHNIQUES IN IMPROVING THERMAL & DAYLIGHTING PERFORMANCE WHILE REDUCING THE ENERGY CONSUMPTION

AN ARCHITECTURAL DISSERTATION, 2017-18, BY AKARSHAN CHAUHAN FOURTH YEAR, BATCH 2014-19 ENROLLMENT NO. - 01017601614

GUIDED BY – MRS. JYOTI LUTHRA

SUBMITTED TO THE GRADUATE FACULTY OF VASTU KALA ACADEMY – MR. R.K. SAFAYA MR. V.P. RAORI MR. A.K. MAITRA

VASTU KALA ACADEMY COLLEGE OF ARCHITECTURE GURU GOBIND SINGH INDRAPRASTHA UNIVERSITY

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LIST OF FIGURES Figure no.

Description

1.

Heat exchange processes between a building and external environment

2.

Heat exchange processes between human body and internal environment

3.

Heat transfer processes occurring in a wall

4.

Vegetation used for shading

5.

Orienting longer facades along north

6.

Multiple buildings on site

7.

Tall forms oriented along wind direction

8.

Using wind pressure zones

9.

Mutual Shading through built forms

10.

Shading strategy involving vertical and horizontal fins

11.

Shading through textured facade

12.

Roof shading by solid cover

13.

Roof shading by plant cover

14.

Roof shading by earthen pots

15.

Removable roof shades

16.

Cool Roofs maintaining temperature

17.

Use of roof ponds in preventing solar hear gain

18.

Heat Transmission in a single glazing clear glass

19.

Wind driven cross ventilation

20.

Buoyancy driven stack ventilation

21.

Single-sided ventilation

22.

section showing details of a wind tower

23.

induced ventilation through curved roofs and air vents

24.

Ventilation Techniques at a glance

25.

Heat gain through solar radiation, occupants and equipments

26.

Nocturnal Cooling

27.

Evaporative cooling as recommended by NZEB

28.

Working principle of earth air tunnel

29.

Working principle of earth berming during summer and winter

30.

Cooling Techniques (evaporative)

31.

Daylight Factor used in determining daylight 2

32.

Sidelighting used for daylighting

33.

Low angle sun

34.

Low and high angle sun

35.

Dome shaped skyiights

36.

Various kinds of daylighting methods at a glance

37.

A typical section of a building using the passive design strategies

38.

Minimising S/V ratio

39.

Minimising P/A ratio

40.

Service cores positioning for minimum heat gain

41.

Horizontal Shadow Angle and Vertical Shadow Angle

42.

External Shading devices strategy

43.

Glazing properties relevant for daylight harvesting and energy efficiency

44.

Insulation positioning for air-conditioned and naturally ventilated spaces

45.

Cross Ventilation dependant on size and position of openings

46.

Sashes, Louvres and Canopies

47.

Don’t’s and Do’s regarding positioning of openings horizontally

48.

Creepers as flexible shading devices

49.

Deciduous tress as best shading device for whole building

50.

PEDA Complex, Chandigarh

51.

Torrent Research Centre, Ahmedabad

52.

RETREAT, Gurgaon

53.

Daylighting in RETREAT

54.

TCI Headquarters, Gurgaon

55.

Courtyard serving multiple purposes in Indira Paryavaran Bhawan

56.

Connecting green spaces around the plaza

57.

East elevation of IPB

58.

Indira Paryavaran Bhawan, Lodhi road

59.

ITC Green Centre, Gurgaon

60.

Reflectors in IHC, close view

61.

Reflectors in IHC wide angle view

62.

Greenery inside IHC plaza-1

63.

Greenery inside IHC plaza- 2

LIST OF TABLES 3

Table No. 1.

Description Evaluation System of GRIHA Criteria

2.

Basic Passive Cooling Strategies

3.

Thermal Mass Properties of Common Building Materials

4.

Total Electricity used for lighting purposes in major economic sectors

5.

Development Controls for Indira Paryavaran Bhawan

ACKNOWLEDGEMENT 4

I would first like to thank my thesis guide, Mrs. Jyoti Luthra for all of her help. She patiently answered all of my questions whenever I ran into problems and encouraged me along the way. She consistently allowed this paper to be my own work, but steered me in the right the direction whenever she thought I needed it.

I want to thank my graduate faculty who were in charge of taking our dissertations forward, Mr. R.K. Safaya, Mr. V.P. Raori, Mr. A.K. Maitra, for their support during this research.

Not forgetting my friends who have been with me during these months and have helped in my case studies whenever possible, Poorvi Maheshwari, Manas Khanna, Radhika Mehrotra, Anant Garg, Stuti Lau and Chandra Deepak.

Finally, I must express my profound gratitude to my family for providing me with support and encouragement throughout my years of study so far and especially through the process of researching and writing this dissertation.

CONTENTS 5

1. Introduction 1.1 Hypothesis - 7 1.2 Aim - 7 1.3 Goal - 7 1.4 Objectives - 8 1.5 Scope - 8 1.6 Limitations - 8 1.7 Methodology – 8 2. Green Building Requirements by GRIHA – 9 3. Passive Cooling Architecture 3.1 Terminologies and Definitions - 11 3.2 Passing Cooling Design Strategies - 14 1.Heat Gain Prevention – 15-22 2.Heat Dissipation – 22-28 3.Heat Modification – 29-32 4.Additional Cooling – 32-35 4. Daylighting 4.1 Daylighting and its need - 36 4.2 Sky Conditions - 37 4.3 Design Criteria - 38 4.4 Design Strategies Using Daylight – 38-42 5. Application of the Strategies in our Context 5.1 Overview of the Passive Strategies studied so far - 43 5.2 Passive Design Strategies for Composite Climate in Delhi – 44-53 6. Literature Case Studies 6.1 PEDA Office Complex, Chandigarh – 54-55 6.2 Torrent Research Centre, Ahmedabad - 56 6.3 RETREAT, Gurgaon – 57-58 6.4 TCI Headquarters, Gurgaon – 59-60 7. Live Case Studies 7.1 Indira Paryavaran Bhawan, Lodhi Road – 61-63 7.2 ITC Green Centre, Gurgaon – 64-65 7.3 India Habitat Centre, Lodhi Road – 66-67 8. Inference – 68 9. Bibliography – 69-71

1. INTRODUCTION

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1.1 HYPOTHESIS Buildings are objects ensuring comfort for their inhabitants. A comfortable environment includes thermal comfort and optimum visibility inside the building. The thermal behaviour of buildings is related to various factors, having climate as the top priority.

During summers, buildings are exposed to high solar radiation and high temperatures, leading to overheated conditions, exceeding comfort levels in the interiors. At this time, cooling of buildings is important. Harmony with local climate is the best solution.

Modern buildings, however, do not follow these traditions. Adapting ideas, styles and technologies have lead us to the immense use of mechanical equipment, to most of the cooling needs, even if they can be fulfilled through traditional methods. Air quality needs are being met by mechanical ventilation strategies, leading to the usage of unnecessary amounts of energy. Similarly, a lot of energy is consumed to light up the interiors of the building even during the daytime. It is necessary to use the daylight as much as possible as it not only cuts off the extra energy consumption but daylighting is also responsible for having positive impact on the health of the occupants. It helps in increasing focus and concentration unlike in the case of mechanical lighting. It has a direct impact on well-being, productivity, and overall sense of satisfaction.

The dissertation thus questions the context and significance of passive design techniques and their feasibility in the Indian context. Design strategies appropriate for composite climate will be talked about in thermal context i.e. specifically passive cooling as well as in daylighting context.

The dissertation will help in understanding that a comfortable working environment can be achieved with the minimum use of mechanical methods and with maximisation of daylighting and passive cooling methods.

1.2 AIM – To reduce the carbon footprint of modern office buildings.

1.3 GOAL – To understand that a comfortable working environment inside an office building can be achieved without consuming energy at an un-sustainable rate by maximum use of passive design techniques and minimum use of conventional HVAC and mechanical lighting. Thus, reducing the carbon footprint of a building and at the same time, not compromising with the comfort of the occupants.

1.4 OBJECTIVES –

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1. To tell about the harmful impact of using conventional methods of lighting and airconditioning at the present rate.

2. To tell about the various guidelines mentioned in GRIHA manual and ECBC about lighting, ventilation and air-conditioning for office buildings for a green rated building.

3. To reveal about various passive design strategies that could be used for thermal and lighting improvements without increasing the carbon footprint of the building.

4. To give examples of various buildings that have successfully used passive design elements and cut down heavily on energy consumption, then compare it to the conventional buildings’ energy consumption, from india and other countries as well.

5. To sample live case studies of various green buildings in and around the city that have good examples of these passive design elements and investigate the possibilities of using them in the existing office buildings around the city.

1.5 SCOPE – The study will only cover all types of office buildings in composite climate. And it will only talk about passive cooling and daylighting strategies. The strategies talked about in this study will be especially suitable for Delhi.

1.6 LIMITATIONS – 1. The study is limited to composite climate and specifically New Delhi. For thermal performance, only passive cooling methods will be talked about and not passive heating methods.

2. Due to the non-availability and lack of time, accurate numeric data may not be used and thus in that case approximate findings shall be there.

1.7 METHODOLOGY – 1. To study the existing lighting and HVAC methods used in the buildings and their harmful impacts.

2. To study the guidelines mentioned in GRIHA manual and ECBC about Air-conditioning, lighting and ventilation of office buildings.

3. To study about various passive design strategies that can be used for maintaining thermal comfort and providing lighting inside the buildings.

4. To search and study various examples of buildings that have successfully used many of these strategies and have cut down heavily on energy demand. This shall include numeric data to give comparison between the expenditure on energy consumptions of these buildings with the conventional ones. This will include both literature and live case studies.

5. To study about integrating the passive strategies with the existing buildings, keeping in mind Indian context and the composite climate of Delhi.

2. GREEN BUILDING REQUIREMENTS AS STATED BY GRIHA 8

2.1 EVALUATION SYSTEM OF GRIHA – (only the ones valid in our context)

S.no Criteria 13

Description

Optimize building design to reduce conventional energy demand Criteria 14 Optimize energy performance of building within specified comfort limits Criteria 17 Use low-energy material in interiors Criteria 18 Renewable energy utilization Total Grand Total Table1: Evaluation System of GRIHA Criteria1

Points 8 16

4 5 33 104

The Criterion valid in our context amounts for around 38% of the overall evaluation criteria for a building proposed to be a green building.

CRITERIA 13 - Optimize building design to reduce conventional energy demand ObjectiveTo apply climate responsive building design measures, including day-lighting and efficient artificial lighting design, in order to reduce the conventional energy demand.

13.1 In order to optimize the building design appropriate climate responsive design strategies should be adopted, such as1. Optimize the orientation of the building; and/ or 2. Place the buffer spaces (such as- toilets, corridors, staircases, lifts and service areas etc.) along western and eastern facades and/ or 3. Provide maximum openings on North and South; and/or 4. Shade the building surfaces getting maximum solar exposure (such as– wall, roof, courtyard) with the use of external shading devices; eg. space frame, jallis, pergola, trees, green wall, terrace garden etc. and/ or 5. Design appropriate shading for all the fenestrations getting direct solar radiation by using sun path analysis or shading norms (prescribed in the table-9 & 10 of Handbook on functional requirements of buildings other than industrial buildings) etc.

13.2 The WWR (window to wall ratio) is limited to a maximum of 60% of gross wall area and the SRR (skylight to roof ratio) is limited to a maximum of 5% of gross roof area as prescribed in Energy Conservation Building Code (ECBC)-2007.

1 (GRIHA, 2017)

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13.3 Ensure that the total daylighted area of the proposed building is > 25% of the total living area and achieve the recommended daylight factor (DF) at the centre of the daylighted area or the average on the daylighted area in a design sky to fetch two mandatory points.

CRITERIA 14 - Optimize energy performance of building within specified comfort limits Objective To optimize use of energy systems in buildings that maintain a specified indoor climate conducive to the functional requirements of the building.

CRITERIA 17 - Use low-energy material in interiors Objective To use low-energy/recycled materials/finishes/products in the interiors, which minimize the use of wood as a natural resource. To use low-energy materials and products, such as composite wood products/renewable materials/reused wood/low embodied energy products/products which utilize industrial waste/recycled products.

The various interior finishes used in the sub-system of the building or the interior, which serve the aim of the credit, have been divided into the following three major categories. If any interior finish, acclaimed for credit, falls beyond this classification, the applicant has to clearly confirm the criteria that meet the requirements of the credit.

Sub-assembly/internal partitions/interior wood finishes/panelling/false ceiling/in-built furniture/ cabinetry flooring doors/windows and frames.

CRITERIA 18 - Renewable energy utilization Objective To use renewable energy sources in buildings to reduce the use of conventional/fossil-fuel-based energy resources.

3. PASSIVE COOLING ARCHITECTURE 10

3.1 TERMINOLOGIES AND DEFINITIONS Thermal Performance of a building - The thermal performance of a building refers to the process of modelling the energy-transfer between a building and its surroundings.

For a conditioned building, it estimates the heating and cooling load so that the sizing and selection of HVAC equipment can be correctly made.

For a non-conditioned building or if we like to incorporate passive techniques as in this study, thermal performance tells about the temperature variation inside the building over a specified period of time and hence, helps in calculating the duration of uncomfortable periods. These calculations help in determining what techniques can be used and their effectiveness in that building, helping in providing energy efficient design model. 2 Various heat exchange processes are possible between a building and the external environment -

Figure1- Heat exchange processes between a building and external environment

Figure2- Heat exchange processes between human body and internal environment Thermal Performance of a building depends upon number of factors1. DESIGN VARIABLES 1.1 Shape and Orientation of the building 1.2 Size of the openings 2 (THERMAL PERFORMANCE OF BUILDINGS, 2017)

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1.3 Dimensions of shading devices, etc.

2. MATERIAL PROPERTIES 2.1 Density, Specific heat, thermal conductivity, transmissivity, etc.

3. WEATHER DATA 3.1 Solar Radiation and Ambient Temperature 3.2 Wind Speed 3.3 Humidity, etc.

4. BUILDING’S USAGE DATA 4.1 Internal heat gains due to occupants, lighting and equipment 4.2 Air exchanges, etc.

To understand the process of heat conduction, convection and radiation occurring in a building, consider a wall having one surface exposed to solar radiation and the other surface facing a room -

Figure3- Heat transfer processes occurring in a wall

HEAT TRANSFER occurs through -

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I.

CONDUCTION - Thermal conduction is the process of heat transfer from one part of a body at a higher temperature to another (or between bodies in direct contact) at a lower temperature.

II.

CONVECTION - The convection is the transfer of heat from one part of a fluid (gas or liquid) to another part at a lower temperature by mixing of fluid particles. Heat transfer by convection takes place at the surfaces of walls, floors and roofs.

III.

RADIATION - Radiation is the heat transfer from a body by virtue of its temperature; it increases as temperature of the body increases. It does not require any material medium for propagation.

IV.

EVAPORATION - Evaporation generally refers to the removal of water by vaporisation from aqueous solutions of non-volatile substances. It takes place continuously at all temperatures and increases as the temperature is raised. Increase in the wind speed also causes increased rates of evaporation. The latent heat required for vaporisation is taken up partly from the surroundings and partly from the liquid itself. Evaporation thus causes cooling.

SOLAR RADIATION The sun is the only source of heat and light for the entire solar system.

Solar radiation is received on the earth’s surface after undergoing various mechanisms of attenuation, reflection and scattering in the earth’s atmosphere. Consequently, two types of radiation are received at the earth’s surface: one that is received from the sun without change of direction, called beam radiation, and the other whose direction has been changed by scattering and reflection, called diffuse radiation. The sum of these two types is known as total or global radiation.

PASSIVE COOLING SYSTEMS – A passive cooling system uses elements of the building to store and distribute energy and when prevailing conditions are favourable to discharge heat to the cooler parts of the environment like the sky, atmosphere and ground. Since the collection, discharge, storage and distribution of energy is generally accomplished by the architectural elements and features of the building, the passive cooling system components are not easily distinguishable from the remainder of the structure.

A space cooling system generally is composed of – i.

A space [or, more specifically, contents] to be cooled ii.

Thermal storage [this may be nothing more than the normal thermal capacity of the building mass]

iii.

An environmental sink [sky, atmosphere or ground] to which heat is discharged

3.2 PASSIVE COOLING DESIGN STRATEGIES 13

The first step to achieve passive cooling in a building is to reduce unnecessary thermal loads that might enter it. Usually, there are two types of thermal loadsi.

Exterior loads due to the climate ii.

Internal loads due to people, appliances, cooking, bathing, lights etc.

Depending on the weather, the thermal load enters into a building in three major ways: i.

Penetration of direct beam sunlight ii.

Conduction of heat through walls and roofs iii.

Infiltration of outside air3

HEAT GAIN PREVENTION

HEAT DISSIPATION

HEAT MODIFICATION

ADDITONAL COOLING

Reduction of penetration of direct sun

Natural Ventilation

Reduction of conduction of heat through walls and roofs

Earth contact buildings

Reduction of infiltration of hot air from outside

Evaporative cooling, Ground cooling, Radiative cooling

Table2 : Basic Passive Cooling Strategies

1. Heat gain prevention techniques –

3 (Sharma, 2003)

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The interaction of solar radiation by the building is the source of maximum heat gain inside the building space. The natural way to cool a building, therefore, is to minimise the incident solar radiation4 1.1 Microclimate Climate is the average of the atmospheric conditions over an extended time over a large region.

Small-scale patterns of climate, resulting from the influence of topography, soil structure, ground and urban forms, are known as microclimates. The principal parameters characterizing climate are air temperature, humidity, precipitation and wind.

The climate of cities differs from the climate of the surrounding rural areas, due mainly to the structure of cities and the heat released by vehicles. In general, the climate in cities is characterized by ambient temperatures, reduced relative humidity, reduced wind speed and reduced received direct solar radiation.

The microclimate of an urban area can be modified by appropriate landscaping techniques, with the use of vegetation and water surfaces, and can be applied to public places, such as parks, playgrounds and streets.

The first stage in managing higher future internal temperatures in buildings is to attempt to make the external air as cool as possible. Within the built environment this involves enhancing the green and blue infrastructure of parks, trees, open spaces, open water and water features. There is a growing interest in the use of rooftop gardens, green walls and green roofs for their cooling effect.

Parks and other open green spaces can be beneficial through their cooling effects in summer, through shading and transpiration, and improved access for natural wind-driven ventilation. In addition, the presence of water, plants and trees contributes to microclimate cooling, and is an important source of moisture within the mostly arid urban environment. Urban surfaces should be cool or reflective to limit solar gain. Pavements, car parks and roads can be constructed with lighter finishes and have more porous structures.

1.1.1

Vegetation

Vegetation modifies the microclimate and the energy use of buildings by lowering the air and surface temperatures and increasing the relative humidity of the air. Furthermore, plants can control air pollution, filter the dust and reduce the level of nuisance from noise sources.

Indoor simulations still tend to be isolated from an important element affecting urban microclimate, such as urban trees. The main advantage of urban trees, as a bioclimatic responsive design element is to produce shade, whereas its main disadvantage is blocking the wind.

In addition, the effects of specific urban tree types - for example, the different leaf area densities and evapotranspiration rates of urban trees influence solar access and heat exchanges if planted around buildings.

4 (Kamal, 2012)

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Figure 4- Vegetation can be used for shading, altering the microclimate and modifying the wind direction.

Selecting the appropriate variety of plantation and its placement are key factors that determine how well the vegetation will serve its intended purpose. (NZEB.in)5

1.1.2

Water Surfaces

Water surfaces modify the microclimate of the surrounding area, reducing the ambient air temperature, either by evaporation, or by the contact of the hot air with the cooler water surface.

Fountains, ponds, streams, waterfalls or mist sprays may be used as cooling sources, for lowering the temperature of the outdoor air and of the air entering the building.

The asphalt and concrete used in urban environments is typically too dense to allow water permeability, and therefore, drastically limits the latent heat exchange. The water and air passage allows latent heat exchange, and therefore decreases the temperature of the pavement. This, in turn, assists trees and other landscape root systems to better access air and nutrients, providing cooler root zones which result in larger and denser shading landscape materials 1.2 Solar Control Solar radiation reaches the external surfaces of a building in direct, diffuse and reflected forms and penetrates to the interior through transparent elements. In general, incident radiation varies with geographic latitude, the altitude above sea level, the general atmospheric conditions, the day of the year, and the time of the day. For a given surface, incident radiation varies with the orientation and the surface’s angle to the horizontal plane.

The admission of solar radiation into an interior space may cause problems, such as high indoor temperatures, thermal and visual discomfort to the occupants, damage to sensitive objects and furnishings. Thus, it is of vital importance that solar radiation should be controlled. Solar control denotes the complete or partial, permanent or temporary exclusion of solar radiation from building surfaces or interior or surrounding spaces. Solar control may be achieved through the following techniques.

5 (NZEB, 2017)

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1.2.1

Form and Orientation of Building –

Maximum solar radiation is interrupted by the roof (horizontal surface) followed by the east and west walls and then the north wall during the summer period, when the south oriented wall receives minimum radiation. It is therefore desirable that the building is oriented with the longest walls facing north and south, so that only short walls face east and west. Thus only the smallest wall areas are exposed to intense morning and evening sun.

Figure 5 - Orient longer facades along the north. This will provide glare-free light in summer from north without shading and winter sun penetration from the south. (as recommended by nzeb.in)

Figure 6 - If a site has multiple buildings, they should be arranged in ascending order of their heights and be built on stilts to allow ventilation.

Place buildings at a 30 or 45 degree angle to the direction of wind for enhanced ventilation. Form can be staggered in the wind facing direction also to achieve the same result.

Figure 7 - Taller forms in the wind direction of prevailing wind can alter the wind movement pattern for low lying buildings behind them.

Figure 8 (All figures as recommended by nzeb.in) 1.2.2

Shading by Neighbouring Buildings –

The buildings in a cluster can be spaced such that they shade each other mutually. The amount and effectiveness of the shading, however, depends on the type of building clusters. Building clusters can 17

be divided into three basic types, ie, pavilions, streets and courts. Pavilions are isolated buildings, single or in clusters, surrounded by large open spaces. Street, long building blocks arranged in parallel rows, separated by actual streets in open spaces and courts are defined as open spaces surrounded by buildings on all sides.

Figure 9 - Mutual shading through built forms (nzeb.in) 1.2.3

Shading by Vegetation –

Shading by trees and vegetation is a very effective method of cooling the ambient hot air and protecting the building from solar radiation. The solar radiation absorbed by the leaves is mainly utilized for photosynthesis and evaporative heat losses. A part of the solar radiation is stored as heat by the fluids in the plants or trees. The best place to plant shady trees is to be decided by observing which windows admit the most sunshine during peak hours in a single day in the hottest months.

Usually east and west oriented windows and walls receive about 50% more sunshine than the north and south oriented windows/walls. Trees should be planted at positions determined by lines from the centres of the windows on the west or east walls toward the position of the sun at the designated hour and date. On the south side only deciduous trees should be planted.

1.2.4

Shelter Against Hot Winds –

Hot winds during summer in hot and dry climatic conditionsare a source of large convective heat gain and a source of extreme thermal discomfort. Wind shelter for a building can be provided by taking the advantage of the existing topography, such as an elevated landmass or by creating wind barriers in the form of trees, shrubs, fences or walls. Usually, an opaque barrier creates a turbulent flow of wind and one has to avoid the accumulation of heat from the sun-irradiated surfaces between the barrier and the surface.

1.2.5

Shading by Overhangs, Louvers and Textured Façade –

The devices which provide shading to an opening can be classified into three types: (i) movable opaque, e.g., roller blind, curtain etc. can be highly effective in reducing solar gains but eliminates view and impedes air movement; (ii) louvers which may be adjustable or fixed affect view and air movement to some degree and provide security; and (iii) fixed overhangs: easy to attain on single storey buildings with overhanging roof.

Also gives rain protection to walls and openings and has little or no effect on view and air movement.

Maximum solar radiation in summer is incident on the roof. It is, therefore, advisable to protect the roof from the sun as far as possible.

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Figure 10 - the shading strategy (vertical fins, horizontal slabs, covered courtyards) has been determined by developing a building model to predict the shading that will be provided by each of the strategies.

External shading is orientation specific and can be effectively integrated into the building envelope if designed keep this factor in mind.

(NZEB.in)

Figure 11- shading due to textured facade 1.2.6

Reflecting Surfaces

If the external surfaces of the building are painted with such colours that reflect solar radiation (in order to have minimum absorption), but the emission in the long wave region is high, then the heat flux transmitted into the building is reduced considerably.

1.2.7

Building Surface Cooling

Cooling of building surfaces by evaporation of water provides heat sink for the room air for dissipation of heat. Maintenance of water film over the surface of building element especially the roof brings down its temperature below the wet-bulb temperature of the ambient air even in the presence of solar radiation thus making the roof surface to act as a means of heat transmission from inside the building to the ambient air without increasing the humidity of the room air.

Roof surface evaporative cooling consists of maintaining a uniform thin film of water on the roof terraces of buildings. This causes the roof temperature to achieve a much lower value than the other elements. The roof evaporation process can be very effective in hot and dry and also in warm and humid climate zones because of the incident solar radiation. The effect of roof surface cooling depends on the type of construction.

1.2.8

Shading of Roof and Walls

Surface shading can be provided as an integral part of the building element or by the use of a separate cover. Highly textured walls have portions of their surfaces in the shade. The radiation absorbing area of such a textured surface is less than its radiation emitting area and therefore it will be cooler than a flat surface. The increased surface area will also result in an increased coefficient of 19

convective heat transfer, which will permit the building to cool down faster at night when the ambient temperature is lower than the building temperature.

Figure 12 - Roof shading by solid cover An alternative method is to provide a cover of deciduous plants or creepers. Because of the evaporation from the leaf surfaces, the temperature of such a cover will be lower than the daytime air temperature and at night it may even be lower than the sky temperature as in the figure.

In addition to shading, this arrangement provides an increased surface area for radiative emission, and an insulting cover of still air over the roof which impedes heat flow into the building, while still permitting upward heat flow at night.

Figure 13- Roof shading by plant cover Although, the system of earthen pots is thermally efficient, the method suffers from practical difficulties because the roof is rendered unusable and its maintenance is difficult. An effective roofshading device is a removable canvas cover. This can be mounted close to the roof in the daytime and at night it can be rolled up to permit radiative cooling.

Figure 14- Roof shading by earthen pots

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Another inexpensive and effective device is a removable canvas cover mounted close to the roof.

During daytime it prevents entry of heat and its removal at night, radiative cooling. Figure below shows the working principle of removable roof shades. Painting of the canvas white minimizes the radiative and conductive heat gain.

Figure 15 - Removable roof shades 1.3 Roofing Techniques – A building can cope up with seasonal weather changes by tuning itself to the heat sources or heat sinks with which it is coupled. The heat sources should be at temperatures higher than the temperatures inside the building, whereas the heat sink must be at a lower temperature. Usual heat sources are sun or the earth, while the heat sinks are the ambient air, radiant sky and the earth.

Figure shows the traditional and modern roofing techniques.

Figure 16 - Cool roofs maintain a temperature difference of at least 6-8 degrees between outside and inside temperature due to high thermal emittance and solar reflectance. (as in NZEB.in)

1.3.1

Roof Ponds 21

Water stored on the roof acts as a heat source and heat sink both during winter and summer climatic conditions. The thermal resistance of the roof in this system is kept very small. In summer during the day, the reflecting insulation keeps the solar heat away from water, which keeps receiving heat through the roof from the space below it thereby cooling it. In the night, the insulation is removed and water, despite cooling the living space below, gets cooler on account of heat losses by evaporation, convection and radiation. Thus, the water regains its capacity to cool the living space. In winter, the insulation is removed during the day. Water and black surface of the roof absorb solar radiation; the living space continues to receive heat through the roof. During night water is covered with insulation to reduce heat losses. 6

Figure 17 - Use of roof ponds in preventing solar gain during daytime and cooling during night-time.

2. Heat Dissipation Techniques – In many cases, the avoidance and modulation of heat gains cannot maintain indoor temperatures at a control level. A more advanced cooling strategy includes heat rejection to heat sinks, such as the upper atmosphere and the ambient sky, by the natural processes of heat transfer. The design of a building is a very important factor which influences the cooling potential of a natural cooling technique. Natural cooling refers to the use of natural heat sinks for excess heat dissipation from interior spaces, including: natural ventilation, evaporative cooling, ground cooling and radiative cooling, and also the use of a PCM based system for free cooling 2.1 Windows Windows play a dominant role in inducing indoor ventilation due to wind forces. Various parameters that affect ventilation are climate; wind direction; area of fenestration/location; size of inlet and outlet openings; volume of the room; shading devices; wire meshes/screens; and internal partitions

6 (Geetha and Velraj, 2012)

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Solar radiation that can penetrate through these fenestrations, especially windows, can lead to considerable heat gain. Glazing in windows traps the heat inside the space.

Window glass allows short wave infra-red radiation from sun to pass through easily, but is very resistant to passage of long wave radiations emitted from objects inside the building that have heated from the solar radiation.

Resultant temperature inside the building can thus be even greater than outside temperature if fenestration systems are not designed carefully.

Figure 18 - Heat Transmission in a single glazing clear glass. (NZEB.in)

As in wind, two forces govern ventilation inside the building: (i) Air moves from high-pressure zone to a low-pressure zone if openings are made on the walls of the respective zones in a building. (ii) If the inlet and outlet are placed at different heights, air flows from the inlet to the outlet due to the density difference created by the upward movement of warm air.

In order to attain sensible air movement, it is essential to provide cross-ventilation. Single sided ventilation allows air movement to a very shallow depth of the building. An alternative is to provide an exhaust for the air via a ridge terminal or chimney or an under floor supply of air to rooms on the leeward side of the building.

2.2 Natural Ventilation Natural ventilation is the most important passive cooling technique. In general, the ventilation of indoor environments is also necessary to maintain the required levels of oxygen and air quality in a space. Traditionally, ventilation requirements were achieved by natural means. In the majority of older buildings, infiltration levels were such as to provide considerable amounts of outdoor air, while additional requirements were satisfied by simply opening the windows. Modern architecture and the energy-conscious design of buildings have reduced air infiltration to a minimum, in an attempt to reduce its impact on the cooling or heating load. Better construction has resulted in buildings being sealed from the outdoor environment. In particular, the construction of large glass office-buildings, which do not allow the opening of windows, has further eliminated the possibility of using natural ventilation for supplying fresh air to indoor spaces. The successful design of a naturally ventilated building requires a good understanding of the air flow patterns around it and the effect of the neighbouring buildings. The objective is to ventilate the largest possible part of the indoor space. The fulfilment of this objective depends on the window location, interior design and wind characteristics.

2.2.1

Wind-driven Cross Ventilation

Wind-driven cross ventilation occurs via ventilation openings on opposite sides of an enclosed space.

Fig. 5 shows a schematic of cross ventilation serving a multi-room building. The building floorspan depth in the direction of the ventilation flow must be limited to effectively remove the heat and pollutants from the space by typical driving forces. A significant difference in wind pressure between 23

the inlet and outlet openings and a minimal internal resistance to flow are needed to ensure sufficient ventilation flow. (Figure 19 below)

2.2.2

Buoyancy-driven Stack Ventilation

Buoyancy-driven stack ventilation or displacement ventilation (DV) relies on density differences to draw cool, outdoor air in at low ventilation openings and exhausts. The figure shows the schematic of stack ventilation for a multi-storied building. A chimney or atrium is frequently used to generate sufficient buoyancy forces to achieve the needed flow. However, even the smallest wind will induce pressure distributions on the building envelope that will also act to drive the airflow. (Figure 20 below)

2.2.3 Single-sided Ventilation Single-sided ventilation typically serves single rooms, and thus, provides a local ventilation solution.

Figure shows a schematic of single-sided ventilation in a multi-room building. The ventilation airflow in this case is driven by room-scale buoyancy effects, small differences in envelope wind pressures.

Consequently, the driving forces for single-sided ventilation tend to be relatively small and highly variable. (Figure 21 below)

24

2.2.4

Wind Tower

Principle The hot ambient air enters the tower through the openings in the tower and is cooled when it comes in contact with the cool tower and thus becomes heavier and sinks down. When an inlet is provided to the rooms with an outlet on the other side there is a draft of cool air. After a whole day of heat exchange, the wind tower becomes warm in the evening.

During night the reverse happens, ie, the cooler ambient air comes in contact with the bottom of the tower through the rooms; it gets heated up by the warm surface of wind tower and begins to rise due to buoyancy, and thus an air flow is maintained in the reverse direction.

Application This system can work very effectively in hot and dry types of climate, where daily variations in temperatures are high with high temperature during day time and low temperature during night time. As a result of clear sky conditions during the night, radiative losses are high. The openings of the wind tower are provided in the direction of the wind, and outlets on the leeward side take advantage of the pressure difference created by wind speed and direction. Normally, the outlets have thrice the area of the inlet for better efficiency. The inlet should be properly designed for uniform distribution.

Figure 22- section showing details of a wind tower

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2.2.5

Solar Chimney

A solar chimney utilizes the stack effect, as already described, but here the air is deliberately heated by solar radiation in order to create an exhaust effect. One should distinguish between the stack effect ventilation due to the building itself, and that due to a solar chimney. In the former case, one tries to keep the increment in the building temperature as small as possible (ventilation is being used for cooling) and hence the stack effect is weak. In the case of a solar chimney, there is no limit to the temperature increment within the chimney, since it is isolated from the used spaces. The chimney can therefore be designed to maximize solar gains and the ventilation effects. The parameters effecting the ventilation rates areheight between inlet and outlet; cross-sectional area of the inlet and the outlet; geometrical construction of the solar absorbing plate; and inclination angle.

Application - The use of solar chimneys is advisable for regions where very low wind speeds exist.

2.2.6

Courtyard Effect

Due to the incident solar radiation in the courtyard, the air in the courtyard becomes warmer and rises up. To replace it, cool air from the ground level flows through the louvered openings of the room, thus producing the air flow.

During the night the process is reversed. As the warm roof surface gets cooled by convection and radiation, a stage is reached when its surface temperature equals the dry bulb temperature of the ambient air. If the roof surfaces are sloped towards an internal courtyard, the cooled air sinks into the court and enters the living space through the low level openings and leaves through higher level openings.

This concept can very well be applied in a warm and humid climate. It is nescessary to ensure that the courtyard gets adequate radiation to produce a draft through the interior. An airflow inside the room can be maintained by a dual courtyard concept, where one courtyard is kept cool by shady trees/ vegetation and another courtyard to sun.

2.2.7

Air Vent 26

A typical vent is a hole cut in the apex of a domed or cylindrical roof. Openings in the protective cap over the vent direct wind across it. When air flows over a curved surface, its velocity increases resulting in lowering of the pressure at the apex of the curved roof, thereby, inducing the hot air under the roof to flow out through the vent.

In this way, air is kept circulating through the room under the roof. Air vents are usually placed over living rooms, often with a pool of water directly under the vent to cool the air, which is moving up to the vent, by evaporation. Air vents are employed in areas where dusty winds make wind towers impractical. It works well both in hot and dry zones and warm and humid zones unlike a wind tower which works only in hot and dry zones. It is most suited for single units which are just above frequently used liveable space.

Figure 23- induced ventilation through curved roofs and air vents

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Fig 24– Ventilation Techniques at a glance7

3. Heat Modification Techniques – 7 (Sharma, 2003)

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The thermal management of a building could be achieved by two methods. In the first method the thermal mass of a building (typically contained in walls, floors, partitions - constructed of materials with high heat capacity) absorbs heat during the day and regulates the magnitude of indoor temperature swings, reduces peak cooling load and transfers a part of the absorbed heat to the ambient in the night hours. The remaining cooling load can then be covered by passive cooling techniques. In the second method the unoccupied building is pre-cooled during the night by night ventilation, and this stored coolness is transferred into the early morning hours of the following day, thus reducing energy consumption for cooling by close to 20%.

TYPE OF DENSITY SPECIFIC HEAT CONDUCTIVITY MATERIAL Kg/m3 J/Kg3 W/mK BRICK 1500-1800 840 0.70 CONCRETE 2500 880 1.28 GRANITE 2750 790 1.7-3.9 GYPSUM 2320 1090 0.35 SOIL 1900 800-1480 0.25-0.30 WOOD 600-900 1300-2400 0.12-0.16 WATER 1000 4182 0.57 GLASS 2580 670-840 0.80 Table 3- Thermal Mass Properties of Common Building Materials

HEAT CAPACITY J/(g.K) 0.84 0.88 0.79 1.09 0.080 1.2-2.3 4.2 0.84

3.1 Shifting of day-heat to night for removal The thermal mass of a building can be achieved either by the use of bulky construction material or by the use of additional energy intensive phase change material in the building system.

Figure 25- Heat gain through solar radiation, occupants and equipment are stored in the thermal mass during daytime.

Concrete slabs, precast ceiling panels, heavy weight mass walls, can add thermal mass to buildings.

(NZEB.in)

3.1.1

Thermal Storage

The structural mass within the existing commercial buildings can be effectively used to reduce operating costs through simple adjustments of zone temperature set points within a range that doesn’t compromise thermal comfort. The cooled mass and higher on-peak zone set point temperatures lead to reduced on-peak cooling loads for the HVAC equipment, which results in lower 29

peak energy and demand charges. The potential for using building thermal mass for load shifting and peak demand reduction has been demonstrated in a number of simulation, laboratory and field studies. This strategy appears to have significant potential for demand reduction if applied within an overall demand response program; because the added demand reduction from different buildings can be large.

3.1.2

Thermal Mass using PCM Based Materials

In order to enhance the thermal storage effect of the building fabric, thermal mass with high thermal inertia, such as phase change materials (PCMs), is advised to be used. The PCM can be integrated into the building fabric to enhance the thermal storage effect and improve the thermal comfort for the inhabitants. Generally speaking, the PCM can be integrated with almost all kinds and components of building envelopes, but different application areas have their own unique configurations and characteristics.

Among all the PCM applications for high performance buildings, the PCM integration in wallboards, roof & ceiling, and windows is most commonly studied, due to its relatively more effective heat exchange area and more convenient implementation.

3.1.3

Conventional Walls and Ceilings

Thermal storage efficiency of a building element depends on the heat storage capacity of various material layers of the building element, the order in which these layers are arranged and also on the fact whether the material is in the steady state or in the transient state. For example, a hanging acoustic ceiling of mineral wool below the roof acts as a lightweight building element for the thermal steady state conditions. During the transient state, however, the concrete room acts as a thermal storage system with appreciable time delay. A larger thermal storage capacity in any case leads to smoothening of the room temperature fluctuation and delays room temperature changes. The thermal performance of a building during the summer time is positively influenced by external as well as internal building elements.

3.1.4

The Vary Therm Wall

Controlling the air movement in magnitude and direction gives rise to wall components with varying thermal resistance. Such a system can be used for mild winter heating and summer cooling for mixed climate as in Delhi. The external wall components are made of light material like aluminium or wood, while the internal component is made of brick (or concrete) wall. The flow of air is controlled into the room or to the ambient by providing proper vents in the interior wall. During the summer daytime, the wall provides effective air insulation and during the night the cool ambient air comes in contact with the warm brick wall and gets heated establishing a natural flow of air. This air movement helps in quick removal of the heat flux. During winter, the vents are opened during the day into the room for supplying warm air and all vents are kept closed during the night time, thus providing an air insulation which minimizes heat losses to the ambient.

Vary therm wall deriving its name from the variable resistance can be operated in three modes: (i) No flow of air in the gap thus effectively reducing the system to an air gap within the wall; (ii) Continuous flow of air into the room or to the atmosphere maintained by natural or forced convection; and (iii) No air flow during the day or night and creating an airflow by opening the vents during night or day time depending on the weather conditions.

3.1.5

Use of night coolness for day-cooling 30

Night ventilation techniques are based on the use of the cool ambient air to decrease the indoor air temperature as well as the temperature of the building’s structure. The cooling efficiency of night ventilation is based mainly on the relative difference between indoor and outdoor temperatures during the night, the air flow rate, the thermal capacity of the building, and the efficient coupling of the air flow and thermal mass.

In recent studies, night ventilation techniques have been applied successfully too many passively cooled or low-energy buildings, particularly in European countries. Several studies reported the results of the monitoring of passive cooling performances applied in different types of buildings.

Figure 26- Nocturnal Cooling: Water or outside air is passed through the building at night to carry the heat stored in the thermal mass during daytime.

4. Additional Cooling Techniques 3.3 Evaporative Cooling

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The heat loss from air (on account of sensible cooling) results in a decreased air temperature, but no change in the water vapour content of the air. Air in the upper part of a wind tower is sensibly cooled. When water is introduced into a system, evaporative cooling occurs. Such cooling involves a change in both the water-vapour content and the temperature of the air. When unsaturated air comes in contact with water, some water is evaporated, thus lowering the temperature of the air and increasing its water-vapour content. A wind-tower system that cools air evaporatively as well as sensibly is particularly effective. Figure 5 shows few of the commonly adopted cooling techniques.

Figure 27- Evaporative cooling as recommended by NZEB (nzeb.in) 3.4 Air Cooling by Tunnels Temperature deep inside the earth remains nearly constant. Daily temperature variations hardly affect the earth’s temperature at a depth of more than one meter, while the seasonal variations of the ambient temperature are strongly dampened by the earth. The earth’s temperature up to a depth of 6 m to 8 m is influenced by the annual ambient temperature variations with a time delay of several months. It is seen that in Delhi the earth’s temperature at a depth of about 4 m is nearly constant at a level of about 23°C throughout the year. A tunnel in the form of pipes or otherwise will acquire the same temperature at its surface causing the ambient air ventilated through this tunnel to get cooled.

3.5 Earth Coupling Because of the thermal storage capacity of earth, the daily and even the annual temperature fluctuation keeps on decreasing with increasing depth below the ground surface. At a depth of 15 m, 32

the earth has a constant temperature of 10°C. The level of water table plays an important role here.

In summer and particularly during the day, the ground temperature is much lower than the ambient air temperature. If a part of the building is earth bermed, the building loses heat to the earth particularly, if the insulation levels are low. The most ancient dwellings were often dug into the ground or covered with earth. Pit houses of North American Indians, Eskimo houses with sturdy timber roofs for supporting earth and a deep covering of snow in winter, and the early Scandinavian farms are few examples of this principle.

3.6 Earth Tunnel Cooling Benefits of ground temperature stabilisation for habitable rooms, food and wine stores have been known since prehistoric times. There are many examples of underground vernacular buildings. The building may be coupled with the earth either by conduction, ie, where the building envelope is in contact with the deep earth by burying or berming. A third medium by which the earth could be coupled with the building is the earth air tunnel, where ventilation supply air is drawn into the building via insulated ducts buried deep into the earth.

Figure 28- Working principle of earth air tunnel 3.7 Earth Berming In an earth sheltered building or earth bermed structure the reduced infiltration of outside air and the additional thermal resistance of the surrounding earth considerably reduces the average thermal load. Further the addition of earth mass of the building acts like a large thermal mass and reduces the fluctuations in the thermal load. Besides reducing solar and convective heat gains, such buildings can also utilize the cooler sub-surface ground as a heat sink. Hence with reference to thermal comfort, an earth sheltered building presents a significant passive approach. Figure below shows the working principle of earth berming during summer and winter conditions.

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Figure 29- Working principle of earth berming during a) Summer and b) Winter 3.8 Desiccant Cooling Desiccant cooling is effective in warm and humid climates. Natural cooling of human body through sweating does not occur in highly humid conditions. Therefore, a person’s tolerance to high temperature is reduced and it becomes desirable to decrease the humidity level. In the desiccant cooling method, desiccant salts or mechanical dehumidifiers are used to reduce humidity in the atmosphere. Materials having high affinity for water are used for dehumidification. They can be solid like silica gel, alumina gel and activated alumina, or liquids like triethylene glycol. Air from the outside enters the unit containing desiccants and is dried adiabatically before entering the living space. The desiccants are regenerated by solar energy. Sometimes, desiccant cooling is employed in conjunction with evaporative cooling, which adjusts the temperature of air to the required comfort level.

3.9 Radiative Cooling Radiative cooling is based on heat loss by long wave radiation emission from one body towards another body of lower temperature, which plays the role of the heat sink. In the case of buildings, the cooled body is the building and the heat sink is the sky, since the sky temperature is lower than the temperatures of most of the objects on earth. This is the mechanism that allows the earth to dissipate the heat received from the sun, so as to maintain its thermal equilibrium. There are two methods of applying radiative cooling in buildings: direct, or passive radiative cooling, and hybrid radiative cooling. In the first, the building envelope radiates towards the sky and gets cooler, producing heat loss from the interior of the building. In the second case, the radiator is not the building envelope, but usually a metal plate. The operation of such a radiator is the opposite of an air flat-plate solar collector. Air is cooled by circulating it under the metal plate, before it is injected into the building. The various concepts of radiative cooling of buildings are explained below.

Paint: The simplest passive radiative cooling technique is to paint the roof white. White paint does not significantly affect the radiation rate at night, since both white and black paints have almost the same emissivity in the long wave range. The advantage of a white painted roof is that by absorbing less solar radiation during the day time, the temperature of the roof remains lower, and can therefore be easily cooled by radiation at night.

Movable insulation: Movable insulation systems are applied on the roof of buildings. They consist of an insulating material that can be moved over the roof of the building. These systems allow the exposure of the thermal mass of the roof to the sky during the night. During the day the mass is covered by an insulating layer to minimize the heat gain in the thermal mass due to solar radiation.

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Movable thermal mass: The movable thermal mass technique is a variation of the previous one, but with an even higher cost. It requires the construction of a thermally insulated pond on the roof of the building with a movable insulation device above it. Between the pond and the roof of the building there is a gap in which the water from the pond can be canalized.

Flat plate air cooler: A flat plate air cooler can be used for cooling water in a loop, similar to the solar collector linked to a storage tank. This is a very simple device, looking almost like a flat-plate air solar collector without glazing. It consists of a horizontal rectangular duct. The top of the duct is the radiator, which is a metal plate. The metal plate should be covered with a material highly emissive in the long wave section of the electromagnetic spectrum, since the

Fig 30 – cooling techniques (evaporative) 35

4. DAYLIGHTING ARCHITECTURE 4.1 DAYLIGHTING AND ITS NEED Lighting is an essential requirement for any facility and it touches the day-to-day lives of people in more ways than one. It accounts for 15% of the total energy consumed in a developing country as against about 7%–10% in developed countries.

India’s installed capacity of power generation is about 112 058 MW (CEA 2004). According to an estimate of the share of electricity used and the lighting component for major sectors (Table 1), about 15% of the total electricity generated is used for lighting purposes in various sectors. 8 SECTOR Industry Commercial/Public Domestic Other

ELECTRICITY USED (%) 49 17 10 24

LIHGTING COMPONENT(%) 4-5 4-5 50-90 2

Table4: Total Electricity used for lighting purposes in major economic sectors

Throughout history, daylight has been a primary source of lighting in buildings, supplemented originally with burned fuels and more recently with electrical energy. Before daylight was supplemented or replaced with electric light in the late 19th-century, consideration of good daylight strategies was essential. As we entered the mid-20th-century, electric light supplanted daylight in buildings in many cases. Fortunately, during the last quarter of the 20th-century and early years of this century, architects and designers have recognized the importance and value of introducing natural light into buildings.9 Daylight can provide a welcome and dynamic contribution to the human experience in buildings and, as demonstrated in recent studies on schools and retail sales environments, can impact human performance. Most people appreciate daylight and also enjoy the outside view that windows provide. Good daylighting design can result in energy savings and can shift peak electrical demand during afternoon hours when daylight availability levels and utility rates are high.

Le Corbusier so clearly identified the importance of light in architecture when he expressed the point that, “Architecture is the masterly, correct and magnificent play of volumes brought together in light ...” emphasizing that “...the history of architecture is the history of the struggle for light.”

8 (Light Right, 2004) 9 (Implications, 2017)

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Figure 31- Daylight factor is used for determining daylight. It is equivalent to the sum of the diffused skylight (SC), internally reflected light (IRC) and externally reflected light (ERC). Quality and quantum of daylight entering a space can be controlled by modifying these three factors 10

4.2 Sky Conditions Season of the year, weather, and time of day combine with predictable movement patterns of the sun to create highly variable and dynamic daylighting conditions. Atmospheric and pollution conditions vary depending on season, weather, and time of day. Daylighting design is usually based on the dominant sky condition and the micro-climate for the building site.

There are three common sky conditions: clear sky, overcast sky, and partly cloudy sky.

The clear sky includes sunshine and is intense and brighter at the horizon than at the zenith, except in the area around the sun. Daylight received within a building is directly dependent upon the sun’s position and the atmospheric conditions. Easily used charts, diagrams, and software programs allow study of solar geometry for any geographic location and time of day.

The overcast sky is characterized by diffuse and variable levels of light and has dense cloud cover over 90% of the sky. It is generally three times brighter overhead (zenith) than at the horizon.

Because direct sun is not present, the brightness of this type of sky depends on sun position.

Generally, higher daylight illuminance occurs at higher solar altitudes.

The partly cloudy sky may have cloud cover that ranges from heavy to light and is similar to the clear sky at one moment and the partly cloudy sky the next. Most designers do not base decisions on the partly cloudy sky because it is constantly changing and therefore, too variable.

10 (NZEB, 2017)

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4.3 Design Criteria The following criteria generally apply to most daylighted buildings. In all cases, specific issues about climate, geographic location, building type, and client preferences may influence the importance of each item. Since LEED certification is of increasing importance, architects and designers should review the credits allowed for daylight and view and for optimizing energy performance for additional items of value during schematic design.

This list is a good place to start at the schematic design phase with appropriate refinements during the design development and construction documents phases.

—Avoid direct sunlight and skylight unless needed for thermal comfort.

—Bounce daylight to create indirect daylight.

—Bring daylight in from above to obtain deeper penetration.

—Filter daylight into buildings.

—Use sustainable design principles.

—Maximize ceiling height to gain better light distribution.

—When appropriate, separate view glass from daylight glass.

—Determine whether daylight is primary or supplementary in lighting design.

—External control strategies offer best light and heat control. Combined strategies of external and internal controls are also practical and are becoming more common.

—Building geometry and interior space planning should promote, rather than preclude, distribution of daylight.

—Locate the maximum number of spaces near daylight through building massing and configuration.

—Create low contrast between window frame and adjacent walls to reduce glare and improve the vision experience. Splaying openings inward can increase distribution of daylight into rooms.

—Integrate building systems, including artificial lighting with daylighting through control systems. 11

4.4 Design Strategies Using Daylight Conceptually, daylighting can be distributed to interior space through openings from the side, from the top, or a combination of the two. Building type, height, aspect ratio and massing, dominant climatic conditions, site obstructions, adjacent buildings, and other issues most often drives choice of strategy.

Throughout history side lighting has been a primary way of introducing daylight into buildings.

Besides supplying light, side lighting can provide view, create orientation, allow connectivity to outofdoors, and allow ventilation during less harsh times of the year.

Daylight openings and external controls should vary by compass direction since each façade of a building, based on orientation, receives differing amounts of daylight throughout the day and across 11 (Implications, 2017)

38

seasons. Location of openings in walls can be low, middle, or high depending on desired distribution and structural and wall system restrictions.

Common strategies are: —Single side lighting from one direction provides a strong directional quality of light with rapid deprecation of light quantity away from the window.

—Bilateral lighting occurs when light enters rooms from two side directions, thus improving uniformity of distribution depending on width of room, height, and location of glass.

—Multilateral lighting enters from several directions and can reduce contrast and glare, improve uniformity of light on horizontal and vertical surfaces, and provide more than one primary daylighting zone.

—Clerestories are high windows with sill heights greater than seven feet above the floor and are excellent strategies for task illumination on horizontal and vertical surfaces. Glass higher on a wall generally provides deeper penetration into a room.

—Light shelves provide shading for middle window positions and re-direct sunlight from high position windows. Light shelves, which separate view glass from daylight glass, are most effective on a building's southern exposure and under clear skies. Light shelves may be external, internal, or a combination of external and internal. Depth of shelves depends on visual needs, orientation, latitude, and window height.

Figure 32- Sidelighting is the most common method of allowing daylight into the building. Glare from direct sunlight can be prevented by using light shelves. These shelves redirect the light rays toward the ceilings which in turn reflect uniform, indirect light. (NZEB.in)

—Borrowed light as a concept allows sharing of light to adjacent spaces when the geometry and depth of perimeter spaces permit. Corridor lighting gained through translucent partitions, glass block, or glass transoms represents a viable concept. Usually borrowed light will supplement or replace electric light during daylight hours when illuminance requirements are low. Security and fire safety influence feasibility of borrowed light.

When daylight penetrates a building from above the ceiling plane or is concentrated in the roof, it is referred to as top lighting. Top lighting can provide greater freedom of source placement to achieve more uniform illumination, takes advantage of high wall surfaces and other architectural elements to distribute light where needed, and increases security and privacy.

39

Splayed openings, for example, can spread the horizontal distribution of daylight over a wider area and reduce contrast associated with glare. The major restrictions for top lighting are the structural design, mechanical system, electrical system, and fire safety layouts. Top lighting is of limited use in tall buildings because it can only illuminate upper floors, unless combined with other strategies.

Common top lighting strategies include: —Skylights placed horizontally in flat or sloped roofs can provide a uniform level of illumination throughout a space when skylights are spaced on a ratio of 1.5 times ceiling height. Skylights are generally effective for lighting horizontal tasks and function best for one-story buildings. The performance of skylights differs under clear versus overcast skies. Thermal gain is an issue in hotter climates.

—Roof monitors are in raised or elevated roof planes. The higher plane contains the monitor which illuminates task areas under each monitor bay. Glazing may be vertical or sloped. North facing monitors perform differently from south facing monitors. Monitors should be avoided on east and west orientations.

—Sawtooths are apertures with vertical or angled glazing installed in a slopped roof plane.

Sawtooths are most effective when used in series of three and were historically used in industrial and manufacturing buildings as the primary light source. Sawtooth slope is generally at a 45 degree angle.

—Courtyards are outdoor areas open to the sky and are partially or totally enclosed by the building.

In partly enclosed courtyards, the north orientation should be the open segment to reduce glare and to reduce the need for sun control. Façade and ground materials should reflect daylight and sunlight without increasing glare for building users.

—Lightwells are openings in the ceiling or floor of a room that allow daylight penetration to the floor, or floors, below. Lightwells are generally utilitarian shafts for daylight and ventilation and are not occupied space. Performance of lightwells depends on depth and the aspect ratio of the shaft. It is best to consider a lightwell as a source of supplementary light.

—Atria are central areas of multi-storied buildings open to the sky. Atria can be glazed to create a controlled environment. Short and wide atria perform better than tall and narrow atria. Performance of atria, like lightwells, is dependent on aspect ratio.

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Figure 33- low angle sun

Skylighting facing the north must be designed with the seasonal sunpaths in mind. Those facing south must allow winter sun to penetrate while north facing should be designed for a high angle sun. Northern light is good for workspace while southern light is more suitable for winter. (NZEB.in) Figure 34- Low and high angle sun

Dome shaped skylights are most suitable for year round daylight from any direction.

Vertical fins can also be added to deflect direct sunlight and reduce glare.

(NZEB.in)

Figure 35- dome shaped skylights (NZEB.in)

Top lighting is an effective daylighting solution for wide buildings where side lighting cannot be used for adequate lighting of the deeper areas of the floorplate. To reduce glare, skylights must be designed with reflective surfaces that redirects direct sunlight into the space. Design of direction specific skylights must take in consideration angle and path of sun during winter and summer. North facing skylights are most suitable for work spaces. (NZEB.in)

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Figure36 - Various kinds of daylighting methods at a glance

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5. APPLICATION OF STRATEGIES IN OUR CONTEXT 5.1 Overview of the Passive Strategies Studied so far

Figure 37- A building incorporating maximum passive design strategies. 12

1-Overhangs (shading device) 2-Fins for shading the south faรงade 3-Green Roof 4-High Performance Glazing 5-Roof Insulation 6-Light-shelves for Daylighting 7-Openings for Natural Ventilation 8-Thermal Mass 9-Evaporative Cooling 10-Cross Ventilation 11-Vegitation for Sun Control

5.2 PASSIVE DESIGN STRATEGIES FOR COMPOSITE CLIMATE IN DELHI 12 (NZEB, 2017)

43

5.2.1 Form and Orientation  



In the climate of Delhi, long facades of buildings oriented towards north-south is the best orientation.

The longer axis of the building (north-south as mentioned above) should be aligned perpendicular to the prevailing winds to facilitate maximum air-flow and cross ventilation in the building. Preferably, buildings can be oriented at an angle between 0 to 30 degrees with respect to the prevailing wind’s direction.

The surface to volume (S/V) ratio of the building should be as low as possible to minimize the heat gain. This is because, compact plans have more efficiency in terms of thermal performance. E.g. a square plan is more thermally efficient than a rectangular plan.

MINIMIZING S/V RATIO – (figure 38 below) Mutual shading of built forms and compact forms i.e. forms with low surface area to volume (S/V) ratio and low perimeter to area (P/A) ratio are ideal for extreme climates. Compact forms gain less heat during daytime and lose less heat at nighttime.

MINIMIZING P/A RATIO – (figure 39 below)

Figures- taken from NZEB.in13

5.2.2. Service Cores

Figure 40 -Service cores can act as thermal buffers against heat gain and loss. Optimal locations for building service cores are in the east and west.

5.2.3

Shading

13 (NZEB, 2017)

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Figure 41- Horizontal Shadow Angle (HAS) and Vertical Shadow Angle (VSA) are used for designing vertical and horizontal shading devices respectively (NZEB.in) 

Firstly, longer sides of the building should be oriented in north-south direction which as told above is preferred to minimize overall solar heat gain through the building envelope.



South facing windows are easiest to shade. Overhangs on south-oriented windows provide effective shading by blocking summer sun and admitting winter sun.



Use fixed horizontal overhangs on south-facing glass. 1m shading device can reduce cooling loads substantially.



To the greatest extent possible, limit the amount of east and west glass (minimize window area) since they are harder to shade. Consider the use of landscaping to shade east and west exposures.



An extended roof can provide shade to the entire north and south wall from the noon sun



Shading is generally not required at the north side. Only cutting the low evening summer sun can be achieved by vertical shades or internal blinds.



On lower buildings, well-placed deciduous trees on the east and west will reduce summer overheating while permitting desirable winter solar gains



Semi-outdoor spaces such as balconies (2.5m – 3m deep) can provide shade and protect interior spaces from overheating and climatic variations. At the same time they act as wind scoops and provide a private social space for the unit.



If no exterior shading is possible, a lower solar heat gain coefficient for the glazing will be mandatory.14

14 (NZEB, 2017)

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Figure 42- External shading devices must be configured according to orientation of the wall and location of the building (latitude). Both decide the time period, both daily and annually, for which the shading will be needed and angle of solar radiation on the wall. Shading masks, graphical representations of shading provided by shading devices, can be then used to design the most suitable strategy for providing shade. (NZEB.in) 5.2.4

Fenestration

Figure 43- v (NZEB.in)

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

Glazing area should be reduced as long as it does not affect the uniformity of daylight distribution in a building.



Reduce Solar Heat Gain Coefficient (SHGC) as less heat will be transferred into the building.



Reduce the U-Value of glazing and also lower the SHGC except for the cold climate where higher SHGC is recommended.



In general cases, specify low U-values for residential applications. Even lower values may be desired in extreme heating climates. For buildings where passive solar heating energy (cold regions) is desired, south-facing windows with high SHGC values coupled with low U-factors should be recommended.



When specifying windows performance, take care to specify “whole product performance values” / whole window unit for U-factor and SHGC.



Use of “glass-only” U-factors should be avoided as they can be 10% to 40% better than the whole product value.

5.2.5

Cool Roofs



Climate is an important consideration when deciding a cool roof installation. Cool roofs achieve the greatest cooling savings in hot climates, but can increase energy costs in colder climates due to reduced beneficial wintertime heat gains.



Roof coatings should include special chemicals that prevent mold or algae growth for a few years. In warm, moist locations, cool roof surfaces can be more susceptible to algae or mold growth than hot roofs.



Proper design techniques should be used to avoid condensation, especially in cold climates.

In cold climates, roofs can accumulate moisture through condensation, and it is possible that cool roofs might be more susceptible to accumulating moisture than dark roofs of the same design.



Decision on cool roofs should be taken by keeping in mind both installation costs (material and labour) and ongoing maintenance costs (repair, recoating, and cleaning). However, in most cases they are considered inexpensive energy efficiency measure in buildings.



Recommendations on cool roof materials includes use of well-graded broken pieces of glossy glazed tiles (broken china mosaic), modified bitumen with plastic and a layer of reinforced material, RCC roof topped with elastomeric cool roof coating or simply finished with broken white glazed tiles.



Slate and tile products are available with solar-reflective surfaces that offer a wide range of cool colours. Additionally, the dense, earthen composition of slate and tile products provide increased thermal mass, yielding additional energy savings not realized through solar reflectance and thermal emittance measures alone.



Concrete and clay tiles may be obtained in white, increasing the solar reflectance to about 70 percent (compared to 20-30 percent range for red tile).



Additional measures like roof insulation, vegetative roofs, and solar panels can be used to inhibit the flow of heat from roof to conditioned space within a building.

47

5.2.6

Insulation

Thermal insulation in walls and roofs reduces heat transfer between the inside and outside and helps maintain comfortable indoor temperature. It provides healthier environment, adds sound control, and most important lowers the electricity bills. Insulation helps keep indoor space cooler in summer months and warm during winters.

There are variety of materials to choose from including fibre glass, mineral wool, rock wool, expanded or extruded polystyrene, cellulose, urethane or phenolic foam boards and cotton. They are generally in the form of amorphous wool or rigid sheets, or require in-situ pouring. Insulation is rated in terms of R-value. Higher R-values denote better insulation and translate into more energy savings, much needed to meet NZEB design goals.

Figure 44- The figure above shows insulation position for air-conditioned and naturally ventilated spaces in a building in warm climate. (coloured red) Insulation should always be placed on the warmer side of the envelope. In warm climates, insulation should be installed on the outside and in cold climates, on the inside.15

15 (NZEB, 2017)

48



Insulation should be placed at the hotter side of the surface (in case of summer cooling, insulation should be on outer side, while in case of heating the building, insulation should be placed on the internal side).



Insulation material should be chosen keeping in mind the following parameters – thermal performance, lifetime performance, fire safety, moisture and condensation, air infiltration and environmental benefits.



Insulation can have a disadvantage that it can prevent the building from cooling at night.



Insulation should be always used with a heat storing material, this storage mass should be placed inside a passively cooled building.



In passive heating or cooling buildings, thermal insulation should be used taking into account the problem of condensation.



When damp proof materials are used, they should always be on the warm side of the insulation.



Use of insulation is more effective in hot climates where demand for cooling is very high.



During summer months in hot climates, thermal insulation must be combined with an effective ventilation strategy at night (when it is cooler) to flush out the heat.



It is recommended for architects to check with air-conditioning system designers to explore the savings provided by an insulated wall.



Providing insulation beyond 100mm thickness does not provide a much further benefit in terms of energy efficiency. Provision of the initial 25mm of insulation, provides the highest incremental energy saving. As the insulation material becomes incrementally thicker, the incremental energy saved becomes smaller and smaller until it is almost insignificant, especially after an insulation thickness of 100mm onwards.

5.2.7

Natural Ventilation

Figure 45- Cross ventilation is dependent on the size and position of openings. Inlets should be in the windward direction and aided with suitably placed outlets that allow egress of wind from the space. (NZEB.in)

49



For good natural ventilation, building openings should be in opposite pressure zone (since natural ventilation rely on pressure to move fresh air through buildings).



The building can be oriented 0° to 30° with respect to the prevailing wind direction (wind rose diagram) / most preferably orientating longer facades of the building towards predominant wind direction.



Maximum air movement is achieved by keeping the sill height at 85% of the critical height.



Greatest flow per unit area of the opening is achieved by keeping the inlet and the outlet of nearly same sizes at nearly same levels.



Windows should be staggered rather than aligned (see fig)



If the space has only one façade exposed to the exterior, it is preferred to provide at least 2 windows on the façade.



Total area of openings should be a minimum of 30% of floor area.



Window-Wall-Ratio (WWR) should not be more than 60%.



Along with orientation to breeze, design of windows to collect direct breezes is important.

Use casement windows to catch and deflect wind from varying angles.

Figure 46- Opening controls like louvers, sashes, canopies and screens can be used to control the direction and velocity of air stream flowing into a space. Comparatively permanent controls like canopies can alter the pressure build up at the face of fenestrations and must be designed keeping this factor in mind. (NZEB.in)

Figure 47- Horizontal placement of openings and internal partitions can alter the direction and spread of air stream. Ideally, openings must be placed in opposite walls, and diagonally but not directly opposite to each other. When placed in walls perpendicular to each other, the inlets and outlets should be at the farthest corners of the walls. (NZEB.in)

50

5.2.8

Vegetation



It is preferable that architects should work with existing terrain of the site, natural topography and local species for appropriate landscaping.



Use of local species for vegetation is highly recommended as they are accustomed to the variations in temperature, rainfall patterns and soil conditions for that region. They are relatively low maintenance in terms of water usage, and are resistant against local pests. In addition, that also support birds and insects that thrive naturally in the region and help maintain the balance of natural flora and fauna.



It is recommended that exotic species should cover no more than 25% of the landscaped area of a building.



Reduce lawn area in the garden to a minimum to reduce the amount of water that is needed for irrigation.

Figure 48 - Creepers are flexible shading devices for verandahs and interior spaces. Depending on the seasonal growth patterns of creepers and timely manual pruning, these can be used effectively for controlling sun penetration.

Figure 49 - Deciduous trees are best for shading parts of the building that need sun in the winter and shade in the summer. They allow sun penetration in winter and block sun access during the summer.

In the northern hemisphere, deciduous trees are best for south facing facades. 16 

Green roofs often require regular maintenance and involve high first costs; thus these have to be designed and installed carefully. On existing buildings, it is more feasible to either use modular blocks or extensive roof systems as these are lighter. Engineered soil that is lightweight, and has better water retention capacity and low organic content is more suitable for green roofs. It is extremely difficult and expensive to repair waterproofing layers once the layers of a green roof are laid. Moreover, the waterproofing in green roofs must be elastic to

16 (NZEB, 2017)

51

withstand building movement and non-biodegradable. Plant native trees and shrubs as they are usually low maintenance.

5.2.9

DAYLIGHTING 5.2.9.1 Orientation and form for daylighting

Buildings can be located and oriented to take advantage of sun’s movement throughout the day, as well as seasonal variations. 

Buildings that are longer on their east-west axis are better for daylighting and visual comfort.



Larger and taller buildings should have thinner profiles to maximize daylighting potential from side windows.



Large buildings can get daylight into more spaces by having central courtyards or atria, or having other cut-outs in the building form.



Focus should be given to maximum daylight factor, increase uniformity of light spread, reduce glare, and minimise solar gains.



Increasing the height of each storey to allow for higher windows also helps pull daylight further into the building.



Plan for daylight by minimising floor plate depth, especially in office buildings.

5.2.9.2 Windows

Amount of daylight that enters a room depends on the window location and its dimensions. 

Determine the window size, height and glazing treatments for each facade separately.



Maximize southern exposure and optimize northern exposure.



North-facing windows provide consistent indirect light with minimal heat gains.



Minimize eastern and western exposure when the sun is lowest and most likely causes glare and overheating. They are more difficult to shade because the sun is closer to the horizon.



There is a direct relationship between the height of the window head and the depth of daylight (Typically adequate daylight will penetrate one and one half times the height of the window head).



Allow daylight penetration high in a space. Windows located high in a wall or in roof monitors and clerestories will result in deeper light penetration and reduces the likelihood of excessive brightness.



Use advanced daylight harvesting methods in case of large window area (such as use of external light shelves, light tubes, a higher ceiling height and other similar technologies, would help to distribute the daylight deeper into the building).



Use skylights and roof monitors to areas without easy access to windows.



Use of light coloured interior surfaces reduces luminance contrast and improves coverage.

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5.2.9.3 Location, Form and Dimensions of Shading Devices 

South-facing windows are the easiest to shade. Horizontal shading devices are most effective as they can block summer sun and admit winter sun.



East- and west-facing windows are best shaded with vertical devices, but these are usually harder to incorporate into a building, and limit views from the window.



The provision of glare protection devices will reduce the amount of daylight harvested. A balance between glare protection and daylight harvesting needs to be done carefully to ensure that the design of the daylight harvesting system will perform as intended.

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6. LITERATURE CASE STUDIES 6.1 PEDA OFFICE COMPLEX, CHANDIGARH Plot size – 1.49 acre Covered Area – 6330 sq.m Basement Area – 2155 sq.m PASSIVE FEATURES – Orientation: Solar Passive Complex has been developed In response to solar geometry i.e. minimizing solar heat gain in cold period. The building envelope attenuates the outside ambient conditions and the large volume of air is naturally conditioned by controlling solar access in response to the climatic swings

Unique Shell Roofing on Central Atrium : The Central atrium of the complex having main entrance, reception, water bodies, cafeteria and sitting place for visitors constructed with hyperbolic shell roof to admit daylight without glare and heat coupled with defused lighting through glass to glass solar panels. The roof is supported with very light weight space frame structure.

Water Bodies: The water bodies with waterfalls and fountains have been placed in the central atrium of the complex for cooling of whole the complex in the hot and dry period.

Light Vaults: The vertical cutouts in the floating slabs are integrated with light vaults and solar activated naturally ventilating, domical structures in the south to admit day light without glare and heat.

Cavity Walls: The complex is a single envelope made up of its outerwalls as double skin walls having 2” cavity in between. The cavity walls facing south and west are filled with further insulation material for efficient thermal effect.

Unique Floating Slab System: The system of floating and overlapping slab with interpenetrating vertical cutouts allow free and quick movement of natural air reducing any suffocating effect.

Landscape Horticulture: The space around the building inside and outside of boundary wall and a big lawn in the south has been designed with trees, shrubs and grass. The big trees along the boundary wall acts as a curtain to minimize air pollution, sound pollution and filter/cool the entry of air.

54

Wind Tower coupled with Solar Chimneys: The wind tower centrally placed coupled with solar chimeys on the domical structures for scientific direct & indirect cooling and scientific drafting of used air.

Insulated Roofing:All the roofs have been insulated with double insulation system to avoid penetration of heat from the roof.

Auditorium:A unique auditorium scientifically designed to control heat penetration, light & sound distribution is placed in the north under the shade of main building.

Big Exhibition Centre:The complex is having a proper designed exhibition centre for display of renewable & non-conventional energy devices / equipments.

Figure 50 - PEDA complex, chandigarh17

6.2 TORRENT RESEARCH CENTRE, AHMEDABAD 17 (PEDA, 2017)

55

India s largest Passive Cooled Building for the past 14 years, with its energy consumption at 1/9th of India s high end consumption and 1/4th of energy benchmark recommended by TERIGRIHA. Passive down draft cooling: The Torrent Research Centre in the hot & dry climate of Ahmedabad had adopted the feature of passive down draft cooling to minimize the use of conventional airconditioning. The design was aimed at integrating spaces requiring highly controlled conditions with those requiring less-controlled conditions while minimizing the presence of dust in the internal environment. Passive cooling is attempted through a system of designated inlets and outlets shafts.

The shafts as a consequence of their locations, sizes, heights, and their complex but stimulated and in-depth researched configuration generated the required movement of air in different spaces without using any mechanical or electrical energy.

The building incurred an additional civil works cost of 13%. However, the savings from the electricity bills have paid back the additional investment in less than one year, and has paid back, in terms of savings, the cost of civil works in less than 13 years of its operation. The savings will be equal to the entire investment of the project in 39 years.

Figure 51 - Torrent Research Centre, Ahmedabad 18

6.3 RETREAT, Gurgaon

18 (Welcometoahmedabad.com, 2017)

56

1997 – 2000 Site Area – 36 hectares = 3,60,000 sqm (Whole GualPahari Campus) Ground Coverage – 3000 sq.m Cost Of Project – Civil works – 23.6 million, Electrical works – 2.5 million, Cost of technologies – 18.54 million Vis-à-vis conventionally designed buildings, RETREAT was constructed at an additional investment of 25% and spends 40%-50% less on energy. Less than 10 kilowatts of energy is used to light the entire complex, with the aid of specially designed skylights, energy-efficient lights, and a sophisticated system of monitoring and controlling the consumption of electricity.

A conventionally designed building of the same scale would use close to 28 kilowatts to provide the same level of lighting. Moreover, the estimated CO2 saving is about 570 tonnes/year.

Various passive design features of this complex enable reduction of space conditioning load by 10%-15% 

The roof is insulated with vermiculite concrete topped with China mosaic for optimal heat reflection.



Walls are insulated with 40-mm thick expanded polystyrene insulations.



The entire complex is south-facing, and deciduous trees all around it provide shade during summer while letting in the sun’s heat during winter by shedding their leaves.



Part of the building is sunken into the ground in order to take advantage of ground storage and thereby stabilize internal temperature.



East and west walls facing walls are devoid of openings and are shaded.



Shading devices and fenestrations are designed to block the summer sun and let in the winter sun.

19

Figure 52 - RETREAT 19 (Sanjayprakash.co.in, 2017)

57

Daylighting Specially designed skylights, energy efficient lights, and a sophisticated system of monitoring and controlling the consumption of electricity illuminate the complex. The conference rooms enjoy glare-free daylight through strategically placed skylights. A master control system switches off the lights automatically whenever it senses that daylight alone is enough to maintain the desired level of illumination. In the living rooms, strategically placed light points and specially designed swivels make it possible to use the light at a study table as well as for bedside reading.

20

Figure 53 – daylighting inside RETREAT

6.4 TCI HEADQUARTERS, GURGAON 20 (Sanjayprakash.co.in, 2017)

58

Year of completion – 1999 Building Area – 2750 sq.m Cost – 55 million Exposure: The Building adopts a compact rectangular form and minimum height above ground to limit exposure to the external conditions. Openings on the external walls are designed for two separate functions: small peep windows at seating height provide for possible cross ventilation and views out; larger windows at ceiling level are designed to distribute glare-free daylight across the office floor.

Taking the daylighting function into account the window area is minimised to 18% of the external wall area.

Both the entrance forecourt and central fountain court, towards which the building envelope opens out with greater transparency, have a structural framework which would provide support for shading screens to be stretched according to seasonal demands.

The planting scheme along the edges of the site with tall evergreen (Silver Oak) trees, provides another protective layer for the building.

Insulation: The orientation of the building is determined by the site. The small peep-windows, due to the deep reveal in which they are set allow insulation in favour of winter, cutting out the mid-summer sun by the shade of the reveal on to the glass. The large daylight windows house adjustable venetian blinds in a double-window sandwich. The blinds are to be adjusted seasonally (three times a year) by the building maintenance staff to control direct insulation and to reflect light towards the ceiling for distribution into the office spaces. The large glazed areas towards the central court and the entrance court rely on screens that will be stretched and gathered seasonally. The structural frameworks enclosing the courts provide the necessary support systems for the screens.

Fountain Court: The fountain is a re-circulating system in which a large body of water flows over extensive surfaces to maximise evaporation. The tall solid concrete columns of broad diameters over which the water trickles down the height of the courtyard, and the thin sheet that overflows the sides of the pool at ground level create a large heat sink and a body of air close to wet-bulb temperature.

The white marble sides of the tank reflect the courtyard light into the basement work areas.

Heat Transfer: In Principle, the building is a heavy mass construction insulated from the outside. Wall insulation is 25 mm thick polyurethane foam protected by a dry red-stone slab cladding system. The roof insulation is 35 mm thick and has a reflective glazed tile paving cover to minimise sol-air temperature on the roof surface. The daylight windows provide insulation by way of tight-sealed two layers of glass with a venetian blind installed between the two layers.

The glazing panels around the inner courtyard however are single glazed - it is anticipated that with the tall water fountain working, the courtyard temperatures would shift substantially toward wet bulb temperature. This would considerably reduce heat load from the courtyard side during summers, and during spring and autumn would act as a heat sink. While the choice of single glazing here evidently means savings in capital expenditure, considering the year-round operation of the fountain court.

Illumination: 59

Daylight is the primary source of illumination. All work spaces receive adequate daylight the maximum distance of a workstation from the daylight source being 5 M. The high windows on the external walls are designed to throw daylight deep into the office space. This is varied seasonally by adjusting venetian blinds installed in the window sandwich to control glare and to modulate distribution.

On the courtyard side fabric screens would be stretched over the structural frame to respond to each season.

External envelope: It is in the deployment of finishing materials of the building that some gains are affected by conscious choice. The criteria for choice of materials was that within the constraints of performance specifications demanded of the surface the material should be chosen from the nearest possible source and should call for minimum processing toward converting or installing it. The external cladding is undressed split red Agra sandstone with pre-cast concrete and terrazzo sills and jambs.

For office areas floors are pre-polished granite from Jhansi (the nearest source to Delhi). For service areas it is Kota stone.

Glass and aluminium are the worst culprits whose areas, sizes and weights are kept to the minimum possible.

21

Figure 54 – TCI Headquarters, Gurgaon

7 LIVE CASE STUDIES 21 (Ashokblallarchitects.com, 2017)

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7.1 INDIRA PARYAVARAN BHAWAN – 2011 – 2014

Size of Plot

9565 sq.m

Maximum Ground Coverage

30%

Basement Area

11826 sq.m

Super Structure Area

19088 sq.m

Plinth Area

30914 sq.m

F.A.R.

200

Set-backs

9m, 6m, 6m, 6m

Height

35m

Car Parking

344

EPI

43.75 kWh/m2/yr

Table5 : Development Controls for IPB22

Building Configuration and Envelope: Passive Means of Reducing Operational Energy The building configuration and the passive design of the building envelope are planned to reduce its operational energy requirements. The building orientation, which is developed primarily as North– South, by dividing it into two long blocks, reduces the heat ingress into the building and develops a shaded central landscaped court (Figure 3). This central courtyard, along with the large lower level punctures into the building envelope, aid in cross ventilation.

Some of the other significant design measures include: I.

II.

III.

The fenestration shading design is appropriate for the entire building and the reduction in the window-to-wall ratio helps to lessen the heat gain as well the need for a high efficiency glass.

The window shading and the courtyard openings are designed to reduce summer heat gain and also to allow in the winter sun. Most of the fenestration and habitable areas are located on the outer periphery, which permits good daylighting and view of the scenic surroundings from most of the locations of the office floorplate.

A large number of spaces including passages and lobbies are developed as nonconditioned spaces with provision for natural cooling and shading through stone jaalis.

These designed stone jaalis also showcase a strong craft tradition of the country

22 (Moef.nic.in, 2017)

61

Figure 55: The courtyard serves multiple purposes. It creates a landscaped connection with the rest of the vegetation on the site, aids cross ventilation within the building and acts as a human interaction area. The hot area escapes easily while the cool air is preserved. 23 I. II.

Maximum Ground Coverage Used (30%) to keep building height comparable to the surroundings Respecting the Eco-logic of the site. Building Punctures & jalis to Aid Cross Ventilation

Figure 56 – Connecting green spaces around the plaza III. IV. V.

Regenerative Architecture keeping the existing balance of nature to connect outdoor greens and the courtyard greens Showcase green bio diversity from Bio-climatic regions of Hot Dry, Composite, Warm Humid, Temperate, Cold Dry & Cold Cloudy Developing Winter Southside sunspaces for office workers + Deciduous trees

Figure 57 – East elevation 23 (Prashad, 2017)

62

Use of materials with low embodied energy –       

AAC Blocks with flyash for recycling and insulation Flyash based Plaster & Mortar Stone and Ferrocement Jalis Local Stone Flooring Bamboo Jute Composite Doors and frames & flooring High Efficiency Glass, high VLT, low SHGC & Low U-value optimized by shading Light Shelves for bringing in diffused sunlight

Figure 58 - Indira Paryavaran Bhawan24

7.2 ITC GREEN CENTRE, GURGAON 24 (NZEB, 2017)

63

Floor Area – 15,800 sq.m Year of completion – 2004 Energy consumption Statistics • Normal building of similar area – 35,00,000 kWh/year • ITC Green Centre – 20,00,000 kWh/year • Annual Energy Savings Rs. 9 Million • % increase in initial cost - 15% Integrative design 

Two office wings are held together by an octagonal central atrium to give it a large L-shaped figure surrounded by an exterior landscaped court.



This L-shape configuration reduces the effective floor width and allows more natural light to penetrate deeper into the building.



The L-shaped blocking also ensures that some part of the façade is always shaded so the load on air-conditioners is reduced.



The central atrium serves many purposes and encourages a sense of community and employee interaction.

Use of glass and energy efficiency 

It was the endeavor of the designers to use an energy-efficient glass for the building since the fundamental requirement of a good work environment is to offer natural light and clear visibility, and only glass can achieve that.



The deep penetration of natural daylight reduces the requirement of artificial lighting, thus increasing energy efficiency.



The special double –glazing used in the ITC Green Center allows maximum natural light in while blocking most of its heat content, thus burden on air-conditioners is reduced. This is the best solution for tropical climatic conditions.



The ITC Green Center achieves a 53% saving on energy consumption, a real feat at the time it was built.



High reflective roof coating with 0.94 emissivity helps interiors to be cooler, saving load on cooling equipment.

64

Building Design 

By giving the ‘L’shape configuration the width of the floor Plate is reduced for the same amount of floor plate area thereby allowing natural light to penetrate deep into the ‘interior spaces The building is a composition of three parts.



Two office wings are held together by a central atrium that as an ensemble creates a large Lshaped figure focused on an exterior landscaped court.



The L-shape blocking ensures that part of the façade is always shaded.



The L-shape office wings end into hexagonal ends that make a very strong presence on the approach roads.



The atrium joins the different functions of the building and connects them into an ensemble encouraging a sense of community and interaction.



The octagonal atrium has side light from the top to provide a glare – free natural lighting in the interior without allowing direct heat gain from the roof.



Interior roller shades to reduce Heat gain.

25

Figure 59 – ITC Green Centre, Gurgaon

25 (ITC Green Centre, 2017)

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7.3 INDIA HABITAT CENTRE, LODHI ROAD

Site Area: 9.6 acres Architect: Jospeh Allen Stein

Ground Coverage: 9549 sq.m First basement: 18819 sq.m Second Basement: 18819 sq.m Approx. cost: 100 crores Parking: 1000 cars

Design Concept of Indian Habitat Centre



The creation of a green and healthy environment forms the backbone of the complex.

This contributes to the urban level functions and also creates a healthy and pleasant environment for the working employees.



The height of the building is around 30m high. The entire facade is cladded with red bricks which give a majestic look to the structure. Vertical and Horizontal ribbon windows have been used with a special glass that restricts the entry of sunlight.

66



The atrium of the structure is beautifully designed with various landscape features such as sculptures, green areas in the centres resulting in the formation of a roundabout in the atrium. The atrium is rectangular in shape and is divided into three parts. The middle one is left open whereas there is landscaped roundabout formation on its either sides.

Shading Devices

The reflectors are installed above the building to provide shade and prevent sun from entering into the building. The reflectors are aligned at an angle which reflect back 70% of the sunlight and change their angle during winter to allow sunlight to fall on the windows.

Figure 60 & 61 – Reflectors above the plaza for shading Orientation    

Building is designed with a view to keep minimum exposure on the east and west site.

North block with number of openings recessed behind two blocks to shade it from NW sun.

Eastern face conveys a fortress like quality.

Building width have been restricted to 15 mts enabling the interiors to be lit from both sides.

Design Overview 



Though of an imposing nature, the building complex manages to blend in with its surroundings through its natural embellishments. In keeping with its habitat theme, the whole complex has been generously provided with natural greenery to provide an undiluted experience of open nature.

The fountain just beyond the second entrance serves purpose not only by being spectacular, but also by relieving the surroundings of the heat.

26 (Shivkumar, Shivkumar, 2017)

67

   

The interesting glass/steel structure near the second entrance provides natural light to the underground parking area.

The building’s two entrances are not one and the same.

The first entrance depicts a seemingly long deep corridor.

The second entrance seems to hide the spacious courtyards.

27

     

(Figure 62 & 63 – greenery inside the plaza.)

The absence of roof gutters rids the complex of clutter. Instead, separations between walls that are lined with tiles facilitates the disposal of rain water.

The roof shading devices not only look spectacular in sky blue, but also serve to block out the Sun’s rays.

The external facade of the Convention centre has a mundane appearance which masks the open inner space.

The courtyards laden with various types of vegetation from tall trees to small shrubs create different spaces.

The presence of an amphitheatre also marks an interesting feature of the complex.

The area without the shading devices is laden with grass lawns to provide a different setting altogether. Construction Technique Massive Steel girders have been for the construction purpose. The entire office block rests on the steel girders without any support of the columns in between the longitudinal plan. Most of the horizontal ribbon windows have slots for plantation purpose which add to the beauty of the entire complex.

8. INFERENCE Air-Conditioning and Lighting, as we all know are two main factors that comes to our mind when we talk about a comfortable working environment, especially in an office building.

The ability to control temperature, humidity, air quality inside the building opened new doors for modern-day architects and designers. This along with electric lighting, eliminated the restrictions that the architects had to face on plan form and fenestrations since ages.

But as the time has passed by and more innovations have been seen in these fields, We have become more and more dependent on the artificial/electric methods to control thermal and lighting performance of the building. We have become used to the luxury of having air-conditioner and lighting fixtures inside our homes and offices and seem to be ignoring the natural ventilation and daylighting completely.

27 (Engineering, 2017)

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However, nowadays countries have started realizing the importance of energy efficiency and have been building sustainable buildings which are green rated by various independent organizations like LEED and GRIHA in India.

When we talk about energy efficiency and making a building net zero energy building, there are mainly two types of design strategies that are involved- active and passive. While active strategies have greater part in meeting the energy requirements because through these we are actually generating energy, but passive elements have always been more important since they help in reducing the energy load of a building considerably if taken care of correctly in the design.

We experience composite climate here in Delhi. But the main extremities of weather are faced in summertime, and maximum scope is there in providing passive cooling methods since not much problem is faced during winters in terms of indoor environment. Therefore, we have talked about only passive cooling methods and daylighting.

The study has mentioned various passive design strategies and how these strategies can be adapted in the climate of Delhi. Many of these techniques can still be incorporated in the existing office buildings around the city, like vegetation around the envelope, green roofs, louvers, etc. while other features can be incorporated when designing new office buildings in the city.

The main objective of this study is to shed light on this sustainable and a better way of designing buildings. With a small increase in initial cost of the building, a lot of savings can be done in the longer run by using these strategies and making the building as energy efficient as possible.

9. BIBLIOGRAPHY (Kamal, 2012) Kamal, M. (2012). An Overview of Passive Cooling Techniques in Buildings: Design Concepts and Architectural Interventions. [ebook] Department of Architecture, Aligarh Muslim University.

Available at: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.301.3850&rep=rep1&type=pdf [Accessed 14 Dec. 2017].

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