Green buildings and bioclimatic design concepts

GREEN BUILDINGS

Compiled byCT.LAKSHMANAN B.Arch., M.C.P.Associate Professor, SRM School of Architecture

Notes on ARC 306 GREEN BUILDINGS : Unit 1

Compiled by CT.Lakshmanan B.Arch., M.C.P. Page 2

UNIT-1 BIO CLIMATIC DESIGN CONCEPTS

Green buildings- salients features- LEED rating systems by IGBC - origin from USGBC – Concept of Sustainable sites – Orientation to sun and Wind -Land form & orientation – Vegetation & Pattern – Water Bodies – Open Space & Built form - Plan form & Elements – Roof form – Fenestration pattern & Configuration .

SUSTAINABLE REAL ESTATE DEVELOPMENT AND GREEN BUILDINGS Sustainable development is defined as ‘Meeting the needs of the present generation without compromising the ability of future generations to meet their needs.’ (Brundtland 1987). The field of sustainable development can be conceptually broken into three constituent parts- social sustainability, environmental sustainability and economic sustainability. The performance of the industrial economy has always been measured through single bottom-line (financial) results. However, striking a balance between environmental, social and economic performance is a key to achieving sustainable outcomes. This has given rise to the concept of triple bottom line.

The real estate industry is one the major energy consumers and GHG emitters. According to a report by the Intergovernmental Panel on Climate Change (IPCC) in 1996, the real estate industry is expected to consume 38% of the global energy and emit 3,800 mega tonnes of GHGs every year. This does not include the usage of other resources such as water. Therefore, the increasing crises of global warming, depleting resources and consumer pressures have pushed the agenda of sustainability in the real estate sector. Growing human activity has increased the concern for sustainability even more in recent times. Sustainability in the real estate context is not only limited to energy conservation, but also includes resource usage, impact on the neighbouring environment and working conditions for tenants. This concern has led to the development of green buildings. The green building concept broadly integrates many interests and aspects of sustainability emphasising reduction of environmental impacts through a holistic approach to land and building uses and construction strategies.



Green Building is described as a structure that ensures efficient use of materials, water, energy and other resources without depletion of nature and minimal generation of non-degradable waste. The term Green Building is often used in combination with 'high-performance building,' 'sustainable design' and 'preserving precious resources.' Although the green buildings concept was prevalent in India from the time of our ancestors who revered the five elements of nature Earth as 'Prithvi,' Water as 'Jal', Agni as 'Energy', Air as 'Vayu', and Sky as 'Akash' but it was lost somewhere A green building uses less energy, water and natural resources than a conventional building. It also creates less waste and provides a healthier living environment for people living inside it compared to a conventional building. Green buildings incorporate several sustainable features such as efficient use of water, energy-efficient and eco-friendly environment, use of renewable energy and recycled/recyclable materials, effective use of landscapes, effective control and building management systems and improved indoor quality for health and comfort. The overall benefits of green buildings mostly depend on the extent to which the sustainable features are addressed during the initial planning and design. A green building is most likely to succeed in its objective if sustainable features are envisioned and incorporated right at the design stage. The design has to take into consideration the entire supply chain—from material sourcing, energy modelling, resource reuse, civic amenities and waste disposal to tenant education. GREEN RATING SYSTEMS The green building movement has led to the emergence of various green rating systems. The predominant ones are:

1. BREEAM - Building Research Establishment Environmental Assessment Method, which is widely used in the UK;

2. LEED- Leadership in Energy and Environmental Design, which was developed by the US

Green Building Council (USGBC) and used in the US;

3. GREEN STAR- developed by the Green Building Council of Australia and used in Australia. The New Zealand Green Building Council have also developed their own version of the Green Star tool;

4. CASBEE- Comprehensive Assessment System for Building Environmental Efficiency, which

was developed by Japan Sustainable Building Consortium and is used in Japan;

5. GREEN MARK- used in Singapore and mandated by the Building & Construction Authority for all new development and retrofit works;

6. NABERS - National Australian Built Environment Rating System managed by the NSW (New

South Wales) Department of Environment and Climate Change. The only rating system to measure ongoing operational performance.



THE GREEN RATING SYSTEMS FOLLOWED IN INDIA ARE: 1. LEED India- administered by the Indian Green Building Council (IGBC); 2. GRIHA -Green Rating for Integrated Habitat Assessment developed by TERI (The Energy and

Research Institute). These tools are relatively new and have not fully evolved. There is no doubt that more and more developers are resorting to these systems to get their buildings certified. Rating systems provide a tool to enable comparison of buildings on their sustainability credentials. Many occupiers and investors are using these tools as a guide to selecting properties for lease or acquisition. Meanwhile, these systems are also being constantly improved. Therefore, the entire green building ecosystem is getting in place. Among all these rating systems, LEED has emerged as the most popular and is followed across 24 countries across the globe, including India. WHY PEOPLE ARE ATTRACTED TOWARDS A GREEN BUILDING This question has been posed to several occupants of a green building. Of all the many reasons, three top reasons often cited by those occupying these buildings are the following: 1. Operational Savings: Green buildings consume atleast 40-50 % less energy and 20-30 % less water

vis-à-vis a conventional building. This comes at an incremental cost of about 5-8 %. The incremental cost gets paid back in 3-5 years time.

2. Daylights & Views: Working in environment with access to daylight and views provides connection to

the exterior environment. This has a soothing effect on the mind. Various studies prove that the productivity of people who have access to day lighting and views is atleast 12-15 % higher.

3. Air Quality: Green buildings are always fresh and healthy. Every green building will have to purge

continuous fresh air to meet the ASHRAE 62 requirements. The green buildings use interior materials with low volatile organic compound (VOC) emissions. A typical office building would require purging of fresh air of about 15 cfm/person which provides a fresh ambience inside the building.

PERCEPTIONS AND REALITIES Having covered on the benefits it is also important to know that people have different perceptions on green buildings; some are correct and some are otherwise. It is important to look at these: Perception #1: Green buildings are costlier Reality: Considerable research and analysis has been carried out with regard to the cost impacts of a green building. The cost could be slightly higher than a conventional building. But then, this needs to be seen with a different paradigm.



The question is how do we compare the costs? There needs to be a baseline cost for all comparisons to be alike. The incremental cost is always relative and depends on the extent of eco-friendly features already considered during design. The incremental cost would appear small if the baseline design is already at a certain level of good eco-design; It would appear huge if the base design has not considered green principles. The second and rather a critical paradigm is to look at the incremental cost in relation to the life cycle cost. This kind of an approach could be revealing. Who knows, buildings would last for a 50 years or 60 years or 100 years!. Over its life cycle, the operating cost would work out to 80-85 % while the incremental cost which is a onetime cost is only 8-10 %. The table below captures the typical payback period in the recently constructed green buildings in India.

There is a decreasing trend in the incremental cost over the years. This trend would continue and we all look forward to the day when the cost of a green building is lower than a conventional building. Perception # 2: Green buildings have to be air-conditioned Reality: Green building concepts and the LEED rating can be applied for non-air conditioning buildings. It has been applied on three such buildings in India viz., IGP office, Gulbarga, the Royal Engineering College, Hyderabad and LIC office, Shimoga. While performing the energy analysis using software tools, such buildings will input the same cooling system both in the baseline and the proposed design. This ensures that the building is recognised for any of the other energy efficiency measures incorporated, for example - the envelop, lighting, roof insulation etc., This kind of an approach also ensures that an apple-to-apple comparison is made while evaluating two green buildings, whether conditioned or not.



Perception # 3: Green buildings take more time Reality: There is a general perception that going the green way may affect the project schedules. This was perhaps the case for the CII-Godrej GBC building when it was the first time that a green building rating tool was being applied in the country. The design in this case took about one-and-half years while the construction was completed in about 9 months ! Thanks to the Green building movement; now there is so much of capacity building that has happened in the country. Now, there is absolutely no difference in the time involved in constructing a green building vis-à-vis a normal building. The time schedule for the rating can be synchronized with that of the building. This has been amply demonstrated in buildings like the Wipro in Gurgaon and Grundfos in Chennai. LESSONS FROM PAST EXPERIENCES With about 40 buildings coming up in the country there have been some key learning in applying the LEED rating system. A few of them are the following: Have the commitment of the entire design team to deliver the rating. Define the role and accountability

of each design member. This can be a good strategy to ensure easy implementation Conceive green by design. Otherwise projects may end up in not being able to apply for certain credits.

For example, it would be almost impossible to achieve daylight credit if the depth of the building has been designed more than 4-5 m.

Freeze the baseline costs right at the beginning so as to realistically evaluate incremental cost due to green aspects. Otherwise, green design can be a easy scapegoat to account for incremental cost due to other factors

Use energy simulation tool right at design stage to decide on material and equipment selection. If this is not taken care initially, it may turn out to be an academic exercise

Certain material related credits viz., low VOC paints, adhesives, sealants, appear easy. So also a few construction related credits like managing construction waste and building flush out. But these require close monitoring and proper documentation ;otherwise a project can lose out on these.

LEED India – Indigenised Rating System for India Eco or green design principles are universal; it cannot be one for USA, one for India and one for Japan. Most of the green building rating systems touch on the same chord – conservation of resources. But the LEED rating system has turned out to be the most versatile and robust. After considering various rating systems, the Indian Green Building Council (IGBC) decided to adopt the LEED rating system. The IGBC is working in India to indigenise the LEED rating system to include the local factors. ‘LEED India’ rating which considers local Indian codes and standards is in an advanced stage of development. The LEED India will follow the following standards:

1. NBC guidelines for: o Erosion & sedimentation control o Rain water harvesting o Safety for workmen during construction



2. MoEF guidelines for large projects 3. CPCB norms for DG set emissions 4. Wild Life Institute of India, Dehradun to define Endangered species 5. Environmental Information System (ENVIS) for Wet lands preservation 6. ECBC for energy baselines

GREEN BUILDINGS IN CHENNAI In India, more and more developers are coming up with green constructions as it is beneficial for them with regards to the construction time and also the cost of the materials used, which is indirectly proportionate to the capita savings costs. Chennai takes pride in having more than 45 structures certified as eco-friendly green buildings by the Indian Green Building Council (IGBC). Chennai is considered to be a green city, with many green buildings when compared to the whole of India. Apart from having many residential green constructions, there are also a lot of companies like Turbo Energy Office Complex in RA Puram, Menon Eternity in Alwarpet and Shell Business Service Centre etc. All of these buildings have been certified with platinum certification, which is considered as the highest rating in India. Platinum rating is followed by gold, silver ratings all of which are based on the sustainability, waste management and usage of natural resources and quality of indoor environment. A few of the gold-rated buildings in Chennai include Anna Centenary Library, Express Avenue Mall and the New Tamil Nadu Assembly building. And a few of the pioneering residential property developers are Green Homes, Akshaya, Pelican Group, Pacifica, Urban Tree and Vivendi Villagio, etc. In Perungudi, the Rane Institute for Employee Development (RIED) building is a silver-rated green building, which is equipped with low-flowing showers, sinks and makes use of solar PV cells to cut down on energy & water consumption. According to the estimation of Indian Green Building Council, Chennai has been experiencing a sharp rise in the number of buildings having green certification in the recent times. OVERVIEW OF THE FIVE ELEMENTS OF A GREEN BUILDING PROJECT… The following pages summarize key principles, strategies and technologies which are associated with the five major elements of green building design which are: Sustainable Site Design; Water Conservation and Quality; Energy and Environment; Indoor Environmental Quality; and Conservation of Materials and Resources. This information supports of the use of the USGBC LEED Green Building Rating System, but focuses on principles and strategies rather than specific solutions or technologies, which are often site specific and will vary from project to project.



FUNDAMENTAL PRINCIPLES OF GREEN BUILDING AND SUSTAINABLE SITE DESIGN 1. SUSTAINABLE SITE DESIGN Key Principles: Minimize urban sprawl and needless destruction of valuable land, habitat and green space, which results from inefficient low-density development. Encourage higher density urban development, urban re-development and urban renewal, and brownfield development as a means to preserve valuable green space. Preserve key environmental assets through careful examination of each site. Engage in a design and construction process that minimizes site disturbance and which values, preserves and actually restores or regenerates valuable habitat, green space and associated eco-systems that are vital to sustaining life. Key Strategies and Technologies: Make more efficient use of space in existing occupied buildings, renovate and re-use existing vacant

buildings, sites, and associated infrastructure and consider re-development of brownfield sites. Design buildings and renovations to maximize future flexibility and reuse thereby expanding useful life.

When new development is unavoidable, steer clear of sites that play a key role in the local or regional ecosystem. Identify and protect valuable greenfield and wetland sites from development.

Recognize that allowing higher density development in urban areas helps to preserve green space and reduce urban sprawl. Invest time and energy in seeking variances and regulatory reform where needed.

Evaluate each site in terms of the location and orientation of buildings and improvements in order to optimize the use of passive solar energy, natural daylighting, and natural breezes and ventilation.

Make best use of existing mass transit systems and make buildings and sites pedestrian and bike friendly, including provisions for safe storage of bicycles. Develop programs and incentives that promote car-pooling including preferred parking for commuters who carpool. Consider making provisions for re-fueling or recharging alternative fuel vehicles.

Help reduce the urban heat island effect by reducing the building and site development footprint, maximizing the use of pervious surfaces, and using light colored roofs, paving, and walkways. Provide natural shading of buildings and paved areas with trees and other landscape features.

Reduce impervious areas by carefully evaluating parking and roadway design. Pursue variances or waivers where local ordinances may unintentionally result in the over-design of roadways or parking.

Optimize the use of on-site storm water treatment and ground water recharge. Minimize the boundaries of the construction area, avoid needless compaction of existing topsoil, and provide effective sedimentation and silt control during all phases of site development and construction.

Use landscape design to preserve and restore the region’s natural habitat and heritage while emphasizing the use of indigenous, hardy, drought resistant trees, shrubs, plants and turf.

Help reduce night-time light pollution by avoiding over-illumination of the site and use low cut-off exterior lighting fixtures which direct light downward, not upward and outward.

2. WATER QUALITY AND CONSERVATION

Key Principles: Preserve the existing natural water cycle and design site and building improvements such that they closely emulate the site’s natural “pre-development” hydrological systems. Emphasis should be placed on retention of storm water and on-site infiltration and ground water recharge using methods that closely emulate



natural systems. Minimize the unnecessary and inefficient use of potable water on the site while maximizing the recycling and reuse of water, including harvested rainwater, storm water, and gray water. Key Strategies and Technologies: Recognize that the least costly, least time consuming and most environmentally preferable design for

site and storm water management is often the one in which the design of buildings and site improvements respect the existing natural flows and features of the land, instead of designing the building and site improvements with total disregard for the site, which results in needless, extensive, disruptive, costly and time consuming excavation and earthmoving.

Conduct a thorough site assessment and strategically locate buildings and site improvements so as to preserve key natural hydrological features. Special effort should be made to preserve areas of the site that serve as natural storm water retention and ground water infiltration and recharge systems. Preserve existing forest and mature vegetation that play a vital role in the natural water cycle by absorbing and disbursing up to 30% of a site’s rainwater through evapo-transpiration.

Minimize the building’s footprint, site improvements and construction area, and minimize excavation, soil disturbance and compaction of existing topsoil as this soil in its natural uncompacted state serves a vital role in absorbing and storing up to 80% of natural rainfall until it can be absorbed by vegetation or enter the site’s natural sub-surface ground water system.

Design and locate buildings and site improvements to optimize use of low-impact storm water technologies such as bio-retention, rain gardens, open grassy swales, pervious bituminous paving, pervious concrete paving and walkways, constructed wetlands, living/vegetated roofs, and other technologies that support on-site retention and ground water recharge or evapo-transpiration. Storm water that leaves the site should be filtered and processed naturally or mechanically to remove trash and debris, oil, grit and suspended solids. Use “hold and release” technologies such as dry retention ponds only as a last resort as these technologies do not preserve the natural water cycle, have little or no benefit in terms of ground water recharge and result in needless additional site disturbance.

Establish a water budget for the building and implement a design that minimizes the use of potable water by using low-flow plumbing fixtures and toilets and waterless urinals. Harvest, process and recycle rainwater, site storm water, and building gray water and identify appropriate uses within the building and site. Use on-site treatment systems that enable use of rain water for hand washing, graywater for toilet flushing, rain and storm water for site irrigation, cooling tower make-up and other uses.

Conserve water and preserve site and ground water quality by using only indigenous, drought resistant and hardy trees, shrubs, plants and turf that require no irrigation, fertilizers, pesticides or herbicides.

3. ENERGY AND ENVIRONMENT

Key Principles: Minimize adverse impacts on the environment (air, water, land, natural resources) through optimized building siting, optimized building design, material selection, and aggressive use of energy conservation measures. Resulting building performance should exceed minimum International Energy Code (IEC) compliance level by 30 to 40% or more. Maximize the use of renewable energy and other low impact energy sources.



Key Strategies and Technologies: Optimize passive solar orientation, building massing and use of external shading devices such that the

design of the building minimizes undesirable solar gains during the summer months while maximizing desirable solar gains during winter months.

Optimize building orientation, massing, shape, design, and interior colors and finishes in order to maximize the use of controlled natural day lighting which significantly reduces artificial lighting energy use thereby reducing the buildings internal cooling load and energy use. Consider the use of light shelf technology.

Use high performance low-e glazing, which can result in significant year round energy savings. Consider insulated double glazing, triple glazing or double pane glazing with a suspended low-e film. Selective coatings offer optimal light transmittance while providing minimal solar gain and minimal heat transmission. Window frames, sashes and curtain wall systems should also be designed for optimum energy performance including the use of multiple thermal breaks to help reduce energy use.

Optimize the value of exterior insulation and the overall thermal performance of the exterior envelope assembly. Consider advanced/high performance envelope building systems such as structural insulated panel systems (SIPS) and insulated concrete form systems (ICF’s) that can be applied to light commercial and institutional buildings. SIPS and ICF’s and other thermally “decoupled” envelope systems will offer the highest energy performance.

Use energy efficient T-8 and T-5 bulbs, high efficiency electronic ballasts, and lighting controls. Consider using indirect ambient lighting with workstation based direct task lighting to improve light quality, reduce glare and improve overall energy performance in general office areas. Incorporate sensors and controls and design circuits so that lighting along perimeter zones and offices can be switched off independently from other interior lights when daylighting is sufficient in perimeter areas.

Use state-of-the art, high efficiency, heating, ventilation and air conditioning (HVAC) and plumbing equipment, chillers, boilers, and water heaters, etc. Use variable speed drives on fan and pump motors. Use heat recovery ventilators and geothermal heat pump technology for up to 40% energy savings.

Avoid the use of HCFC and Halon based refrigeration, cooling and fire suppression systems. Optimize the use of natural ventilation and where practical use evaporative cooling, waste heat and/or solar regenerated desiccant dehumidification or absorption cooling. Identify and use sources of waste energy.

Use Energy Star certified energy efficient appliances, office equipment, lighting and HVAC systems. Consider on-site small-scale wind, solar, and/or fuel cell based energy generation and co-generation.

Purchase environmentally preferable “green” power from certified renewable and sustainable sources. 4. INDOOR ENVIRONMENTAL QUALITY Key Principles: Provide a healthy, comfortable and productive indoor environment for building occupants and visitors. Provide a building design, which affords the best possible conditions in terms of indoor air quality, ventilation, thermal comfort, access to natural ventilation and daylighting, and effective control of the acoustical environment. Key Strategies and Technologies:

Use building materials, adhesives, sealants, finishes and furnishings which do not contain, harbor, generate or release any particulate or gaseous contaminants including volatile organic compounds.



Maximize the use of natural daylighting. Optimize solar orientation and design the building to maximize penetration of natural daylight into interior spaces. Provide shades or daylight controls where needed.

Maximize the use of operable windows and natural ventilation. Provide dedicated engineered ventilation systems that operate independently of the buildings heating and cooling system. Ventilation systems should be capable of effectively removing or treating indoor contaminants while providing adequate amounts of fresh clean make-up air to all occupants and all regions of the building. Monitor indoor air conditions including temperature, humidity and carbon dioxide levels, so that building ventilation systems can respond when space conditions fall outside the optimum range.

Provide a smoke free building. When smoking must be accommodated, provide completely dedicated smoking areas are physically isolated, have dedicated HVAC systems, and remain under negative pressure with respect to all adjoining spaces. Assure that air from smoking areas does not get distributed to other areas of the building does not re-enter the building through doors or vestibules, operable windows, or building fresh air intakes.. Locate outdoor smoking areas so that non-smokers do not have to pass through these areas when using primary building entrances or exits.

Design building envelope and environmental systems that not only treat air temperature and provide adequate ventilation, but which respect all of the environmental conditions which affect human thermal comfort and health, including the mean radiant temperature of interior surfaces, indoor air humidity, indoor air velocity, and indoor air temperature. Following these principles and providing a building that is also responsive to seasonal variations in desirable indoor humidity levels, air velocity, and mean radiant temperatures can also result in significant energy savings as improved occupant comfort results in less energy intensive operation of the buildings air-side heating and cooling system.

Maximize occupant health, comfort and performance by providing occupants with individual space/zone control of heat, ventilation, cooling, day-lighting and artificial lighting whenever possible.

Prevent contamination of the building during construction. Take steps to minimize the creation and spreading of construction dust and dirt. Prevent contamination of the building and the buildings heating, cooling and ventilation systems during the construction process. Protect construction materials from the elements so that they do not become damp, moldy or mildewed.

Provide a clean and healthy building. Use biodegradable and environmentally friendly cleaning agents that do not release VOCs or other harmful agents and residue. Prior to occupancy install new air filters and clean any contaminated ductwork and ventilation equipment. Use fresh outdoor air to naturally or mechanically purge the building of any remaining airborne gaseous or particulate contaminants.

5. MATERIALS AND RESOURCES Key Principles: Minimize the use of non-renewable construction materials and other resources such as energy and water through efficient engineering, design, planning and construction and effective recycling of construction debris. Maximize the use of recycled content materials, modern resource efficient engineered materials, and resource efficient composite type structural systems wherever possible. Maximize the use of re-usable, renewable, sustainably managed, bio-based materials. Remember that human creativity and our abundant



labor force is perhaps our most valuable renewable resource. The best solution is not necessarily the one that requires the least amount of physical work. Key Strategies and Technologies:

Optimize the use of engineered materials which make use of proven engineering principles such as engineered trusses, composite materials and structural systems (concrete/steel, other…), structural insulated panels (stress skin panels), insulated concrete forms, and frost protected shallow foundations which have been proven to provide high strength and durability with the least amount of material.

Identify ways to reduce the amount of materials used and reduce the amount of waste generated through the implementation of a construction waste reduction plan. Adopt a policy of “waste equals food” whereby 75% or more of all construction waste is separated for recycling and used as feedstock for some future product rather than being landfilled. Implement an aggressive construction waste recycling program and provide separate, clearly labeled dumpsters for each recycled material. Train all crews and subcontractors on the policy and enforce compliance.

Identify ways to use high-recycled content materials in the building structure and finishes. Consider everything from blended concrete using fly ash, slag, recycled concrete aggregate, or other admixtures to recycled content materials such as structural steel, ceiling and floor tiles, carpeting, carpet padding, sheathing, and gypsum wallboard. Consider remanufactured office furniture and office partition systems, chairs and furniture with recycled content or parts.

Explore the use of bio-based materials and finishes such as various types of agriboard (sheathing and or insulation board made from agricultural waste and byproducts, including straw, wheat, barley, soy, sunflower shells, peanut shells, and other materials). Some structural insulated panels are now made from bio-based materials. Use lumber and wood products from certified forests where the forest is managed and lumber is harvested using sustainable practices. Use resource efficient engineered wood products in lieu of full dimension lumber which comes from older growth forests.

Evaluate all products and systems used for their ability to be recycled when they reach the end of their useful life. Preference should be given to products and systems that facilitate easy, non-energy intensive separation and recycling with minimal contamination by foreign debris.

Recognize that transportation becomes part of a product or building materials embodied energy. Where practical, specify and use locally harvested, mined and manufactured materials and products to support the regional economy and to reduce transportation, energy use and emissions



Design Sequence (i) Landform: topography and slope orientation (ii) Vegetation type and pattern (iii) Water bodies (iv) Street widths and orientation (v) Open spaces and built spaces (vi) Ground character (vii) Plan form (viii) Plan elements (ix) Building orientation (x) Surface area to volume ratio (xi) Roof form (xii) Fenestration pattern and configuration Level 1 : Landform Orientation

Landform variations and the microclimate. Flat site experience little variation. air speed increases up the slope and decrease down it. Depression valleys experience lower air temperatures. They have little air movement unless they lie in the direction of airflow.

Pressure Difference caused by obstacles

Landform optimization in hot climates: building in a depression and shading from heat and wind minimizes heat gain and discomfort



Protection from katabatic winds on slope; A cool mass of air descending down a slope (katabatic wind) can be deflected or minimized by thick vegetation.Air speeds are greatest on the crest The landform or topography of a site and surrounding could either be flat, sloping or undulating

(mounds etc.). If the land is flat, similar conditions would prevail over the entire site. Slopes and depressions lead to different levels of air temperature and air movement at different parts

of the site. Cool air has a higher density than hot air. As a result cool air is heavier and tends to settle down in

depressions while hot air rises. As a result, the air temperature is lower in such areas. Also air speed increases up the windward slope. Air speed is maximum at the crest and minimum on

the leeward side. Airflow normally takes place from high pressure zones to low pressure zones. Obstacles in the path of

airflow cause an air-buildup and therefore a high pressure area on the windward side. Similarly, direction of the airflow would now depend on the shape of the obstacle and the magnitude of

the pressure difference. Building Design In hot climates building in a depression implies relatively lower air temperatures. When building on a slope, the leeward side is preferable, as long as the orientation is acceptable. In both cases warm breezes would be minimized. The collection of water in a depression might allow for a water body. This would also be beneficial in cooling the place. In humid climates our primary concern is maximizing air movement. We must, therefore, place our building on the top of the windward slope where the air speed would be the highest. In cooler climates not only do we not place our building in the depression we also avoid the path of the cool air down the slope. Here, again, vegetation could help in protecting from cool breezes. Level Two: Landform Orientation

Landform orientation and building placement in hot climates. If the slope is steep or the sun is low, a northern slope may minimize heat gain but this would also cut off winter sun. In some cases earth sheltered construction on the south slope would be the answer



Landform orientation has little meaning when the land is flat. However, the orientation of slopes would make a difference.

In northern latitudes (away from the equator) south slopes receive the most while north slopes receive the least direction radiation.

In the southern latitudes, just the reverse happens. East and west oriented slopes receive direct radiation mostly during the morning and evening, respectively.

Building Design In hot climates, a north slope would be preferable as it would receive the least direct radiation.

However, this is true only if the slope is steep enough to shade the building. As a result slope orientation is of little consequence. The building should be placed so as to maximize airflow.

Hot-dry climates often have cool or cold winters. While the prime need is to minimize heat gain, there is also a period when heating is required. If, therefore, one is building on a sufficiently steep north slope, it would be advisable to build into the slope. This would make the building warmer during winter and cooler during summer.

However, we would be deprived of the pleasure of direct sunshine. The amount of daylight available needs to be considered.

Further, we also need to consider the airflow pattern for the slopes we are building on. Building placement from the point of airflow and that of solar radiation may not always be the same. Often we need to reach a compromise based on greater need.

Level Three: Vegetation Pattern

Vegetation increasing, decreasing and directing airflow

Vegetation causes pressure differences which shifts the air path



It also causes pressure differences, thereby, increasing and decreasing air speed or directing airflow.

Vegetation and trees in particular, very effectively shade and reduce heat gain. Plants, shrubs and trees absorb radiation in the process of photosynthesis. As a result, they actually cool the environment. Trees and hedges also affect airflow. Thick vegetation effectively cut it off.

On the other hand, careful placement of trees and hedges can direct and increase air speeds. This is achieved by planting trees and hedges so as to make a narrowing 'path' for the air. This reduction of area increases air speed. They can, therefore, direct air into a building or deflect it away.

The placement of trees and hedges cause minor pressure differences which marginally changes the air path. This is easy to understand. The leeward side/ wind shadow area is a low pressure zone. Air tends to shift towards this.

Airflow below the canopy of a tree is similarly shifted upwards. The understanding of these pressure changes and the consequent air paths can be used to our advantage in building design.



Building Design In hot-dry climates where heat gain is to be minimized, trees can be used to cut off the east and west sun. Hot breezes can be effectively cut off. Planting deciduous trees is very useful in hot dry climates. They provide comforting shade in summer and shed their foliage in winters allowing sun. In warm humid regions vegetation can be employed to maximize airflow. However, if they are not planted carefully they would end up reducing air speeds. Trees and vegetation would also increase humidity levels. Evergreen trees can be used in cold climates to cut off breezes. However, they would also absorb solar radiation and, thereby, cool the place. Level Four: Water Bodies

Water bodies absorb much heat during the day and reradiate it at night Water absorbs relatively large amount of radiation. They also allow evaporative cooling. As a result, during the daytime areas around water bodies are generally cooler. At night, however, water bodies release relatively large amounts of heat to the surroundings. This heat

can be used for warming purposes. Building Design In hot-dry climates, water / water bodies can be used both for evaporative cooling as well as minimizing heat gain. A roof pond minimizes heat gain through the roof. In cold climates, water bodies are beneficial only if their heat gain and loss can be controlled. This would happen only if the water body can be enclosed by the building. In warm-humid regions water bodies are best avoided. The minimal benefit provided by evaporative cooling would be offset by the heightened humidity levels. However, we may be faced with a large water body in a cold region. The best thing to do then is to stay away from it. The wind pattern would have to be studied and winds avoided either by building location, vegetation pattern or both. Level Five: Street Widths and Orientation

Street widths in hot climates: narrow north-south streets minimize eastern and western radiation.



Arrangement of building blocks to maximize airflow.

Street widths in cold climates. Wide east-west streets maximize the scope for south winter sun. The amount of direct radiation received on the street (and to an extent, on the lower floors) is

determined by the street width. The street width to building height ratio determines the altitude up to which solar radiation can be cut

off. Similarly, the street orientation determines the azimuth up to which solar radiation can be cut off. As a

result they can be used very effectively to minimize or maximize heat gain. Street width to building height ratio also affects the daylight received. Modulating the street width and orientation can very effectively control solar radiation. Building Design In hot-dry climates, the prime need is to minimize heat gain. Small street width to building height ratio ensures narrow streets and, thereby, shading. In particular, streets running north-south should be narrow. This would enable mutual shading from the horizontal morning and evening sun. East-west streets are avoidable as they allow uncomfortably low sun in the mornings and evenings. However, if unavoidable, they too should be narrow. The exact orientation of streets can be determined by considering the solar geometry in combination with building heights. This will enable us to orient the streets such that comfortably low sun is shielded off by the buildings. In warm-humid climates the primary need is for air movement. Streets, should therefore, be oriented to utilize the natural wind patterns. In cold climates, wide streets, especially the east-west streets allow buildings to receive the south sun. However, the need here is not just to gain heat but also conserver that which is received. So settlements should be compactly planned. North-south streets should be narrow. Low building heights are preferred. This would enable heat gain from the roof to be maximized. However, heat loss also has to be minimized.



Level Six: Open Spaces and Built Form

Absorptive surfaces and smaller open spaces radiate less heat to buildings around

Greater the exposure of the walls and ground to the sky, the more the heat loss.

Compact planning in the modern context: Large heat production of modern buildings makes compact planning inappropriate in hot regions due to the decrease in heat loss capacity.

Compact planning in cold climates: while heat gain is reduced by compact planning, the decrease in heat loss is significant. Open spaces in any complex are integral part of built form. After all, any built mass modifies the

microclimate. Large open spaces allow for freer air movement. The built pattern is also important. It can increase, decrease and modify air speeds.



Open spaces gain heat during the day. If the ground is hard and building surfaces are dark in color then much of this radiation is reflected and absorbed by the surrounding buildings. If, however, the ground is soft and green then less heat is reflected.

Shading by surrounding buildings and trees can reduce heat gain to some extent. For summer shading, the building will have to be tall because of the high solar altitude. In winters, on

the other hand, since the sun is at a lower altitude even low buildings would shade large areas. Heat loss at night by re-radiation also increases with more open spaces. During the day, buildings receive radiation from the sun and sky. At night this heat is reradiated to the

sky. The greater the exposure of the buildings to the sky, the more the heat loss. So not just the roof, the walls also lose heat. If, however, buildings are tightly packed then all walls face each other and have little exposure to the sky. Then, heat loss occurs only from the roof.

Building Design In hot-dry climates, compact planning with little or no open spaces would minimize heat gain as well as heat loss. When heat production of the buildings is low, compact planning minimizes heat gain and is desirable. This is how traditional settlements were often planned. However, in modern cities, buildings produce much heat of their own. In such cases heat loss becomes important. In fact, the phenomenon of heat build up in cities leads to the formation of heat islands. The size and scale of open spaces must, therefore, be optimized. Further, surface characteristics are important. The ground should be soft and preferably green. Building surfaces should not be very reflective. Shading by trees or buildings would also reduce heat gain. Since the hot-dry climate might also have a cold season, trees should be deciduous so as to allow winter sun. Compact planning would reduce the scope for daylight, while 'open' planning allows more daylight. In humid climates buildings should preferably not be attached to one another. Streets and the open spaces should be oriented with respect to wind patterns. The open spaces and the funnel effect can be used to maximize airflow within the complex. In cold climates open spaces should be small. Surfaces could be hard and absorptive. Compact planning is, of course, preferred. They should allow the south sun into buildings. Trees, if any, should be deciduous. Level Seven: Ground Character

Different ground materials reflect, store and absorb heat to different degrees Depending on the ground surface, incident radiation can be absorbed, reflected or stored and re-

radiated later.



The color and texture of a material's surface determines its reflectivity. The lighter the color and smoother the surface, more the reflectivity of the material.

The darker the surface and rougher it is, the lower the reflectivity. Such materials would store more heat and reradiate it at a later time. This re-radiation mostly takes place at night when the surroundings are at a lower temperature.

Vegetation, namely, trees, shrubs, plants and grass utilize sunlight for photosynthesis. They absorb and consume the radiation. In this case the heat is neither reflected nor reradiated.

Building Design In hot climates ground surfaces preferably should be green in order to minimize heat gain. Where hard surfaces and paving are unavoidable they should be rough but not very dark. This would make the ground less reflective but not highly absorptive. In humid conditions ground character is of consequence only when it can absorb moisture. In cold climates heat gain would be maximized by reflecting the heat or storing it. Ground surfaces should preferably be paved dark but smooth. This would increase absorptivity and reflectivity. Level Eight: Plan Form

Different plan forms have different perimeter to area ratio

The plan form of a building affects the airflow around and through it. It could either aid or hinder natural

ventilation.



As stated earlier, physical obstacles in the path of airflow create pressure differences. This causes a new airflow pattern.

Air tends to flow from high pressure areas. knowing the direction of air movement, the plan form can be determined also as to create high pressure and low pressure areas.

Building openings connecting the high pressure areas to low pressure areas would cause effective natural ventilation.

The perimeter to area ratio of the building is an important indicator of heat loss and gain. It, therefore plays a role in ventilation, heat loss and heat gain. Smaller the P/A ratio, the lesser will be the heat gain during the day and the lesser the loss at night.

Building Design In hot climates the P/A ratio should be kept to a minimum. This would cause minimum heat gain. Plan form for enhancing ventilation is not a compelling proposition as breezes are often quite warm. In warm-humid climates the prime concern is a plan form for maximizing air movement. Here too, minimizing the P/A ratio is useful as it minimizes heat gain. In cold climates too the P/A ratio should beminimal. This ensures minimum heat loss. Heat gain can often be achieved by solariums etc. Level Nine: Plan Elements

Integration of vegetation in the building to minimize heat gain

Courtyard atrium: Integration of operable glazing at the roof level allows the courtyard to be converted into a heat trap in winter.



Heat trapping systems: Glazing traps heat and the space created could serve as a greenhouse or contain a water body. A water body would act as a thermal mass-storing heat in the day and reradiating in the night.

Wind catchers The role of vegetation, water bodies, radiative heat gain and air movement have been seen at the

overall site level. These elements could be integrated with the building or the building complex for further benefits. In a sense, they can become elements of the design.

Water bodies: As mentioned earlier, water bodies are effective means of evaporative cooling. A high specific heat allows water to absorb a comparatively large quantity of radiation. This also aids in cooling. On the other hand in cooler climates it can act as a heat storage material, especially when enclosed by glazing

Vegetation: It has already been seen that vegetation can absorb radiation and therefore, effect cooling. A greenhouse does just the opposite. It traps heat and helps in warming.

Courtyards and Verandas: These can lead to very airy structures especially when seen in conjunction with the fenestration. Air movement would be desirable in warm-humid conditions. Shaded courtyards can be quite effective as reservoirs of cooler air in hot climates. At night, cool air tends to collect in the court.

Water bodies and vegetation help in cooling a space by evaporation and the absorption of heat. Water bodies and greenhouses also aid in space heating. Courtyards, and in certain cases, wind-towers cause heat loss and enhance ventilation. Thus, plan

elements can help in heating, cooling and even ventilation. Building Design In hot climates, it is very desirable to integrate plant and vegetation, wherever possible, into the plan form. Gardens, roof gardens and planters on windows and shades could well reduce heat gain. If water bodies can be integrated, that too would be beneficial. Further, shaded courtyards would lead to lower air temperatures. In humid climates courtyards and verandas aid in ventilation. Wind catchers, objects of much interest, may also be employed. However, they have to be used with care. They are really effective only when there are strong (often directional) and cool breezes. Such areas are often coastal regions. Here, the sea breeze



in the evening is strong, directional and cool. Water bodies and vegetation can make warm climates uncomfortable due to the humidity In the cooler season also, roof gardens would be desirable. However, water bodies would either have to be drained or enclosed by glazing. Shaded courtyards would, however cause uncomfortable cold. They should either be avoided where winters are severe or have operable glazing at the roof level. Screening off by glazing would cut off cool air and increase heat gain. Fixed glazing would, however be highly inappropriate as during summer it would lead to uncomfortable over heating. In cold climates, heat gain is the primary aim. Greenhouses and glass boxes are very effective heat traps. Level Ten: Building Orientation The building orientation determines the amount of radiation it receives. The orientation, with respect

to air patterns, affects the amount of natural ventilation possible. Building Design In Hot dry climate The buildings should be oriented from solar point of view so that as a whole it should receive the maximum solar radiation in winter and the minimum in summer. Longer walls of building should face north & south. Non-habitat rooms can be located on outer faces to act as thermal barrier. Preferably, the kitchen should be located on leeward side of the building to avoid circulation of hot air and smell from the kitchen. In Warm Humid climate the orientation should be preferably in North-South direction for habitable rooms i.e. longer walls should face north & south so that shorter sides are exposed to direct sunlight. In cold climate the orientation should preferably be in north – south direction i.e longer walls should face north & south to receive more solar heat during winter months. Level Eleven: Surface Area to Volume Ratio

Minimizing the surface area to volume ratio minimizes heat transfer. The surface area to volume (S/V) ratio (the three dimensional extrapolation of the P/A ratio) is an

important factor determining heat loss and gain. The greater the surface area the more the heat gain/ loss through it. So small S/V ratios imply minimum

heat gain and minimum heat loss. Building Design



In hot dry climates S/V ratio should be as low as possible as this would minimize heat gain. In warm-humid climates the prime concern is creating airy spaces. This might not necessarily minimize the S/V ratio. Further, the materials of construction should be such that they do not store heat. In cold-dry climates also S/V ratios should be as low as possible to minimize heat losses. Level Twelve: Roof Form

Various roof forms and their areas of exposure

Roof as a light source

Basic roof forms and their effect on ventilation



The roof can be used as a source of daylight into the building. Daylight can be obtained by either a

horizontal (un shaded) or vertical (shaded) roof lights. By varying the roof projections with respect to the building width pressure differences between the

windward side and leeward sides could either be increased or decreased. This would increase or decrease natural ventilation.

In hot climates un shaded roof lights would be quite undesirable as they would further add to the heat gain.

Building Design In any climatic context, the roof can be relied upon as a means to enhance the light levels indoors. The nature of the roof light would change with the climatic context. In overheated areas, roof lighting would be shaded to prevent heat gain. In under heated areas roof lighting would be unshaded making it a supplementary source of heat. In hot as well as in cold climates the aim is to minimize natural ventilation. In order to minimize this, the building should have as flat a roof as possible and the building width, in the direction of airflow should be as large as possible. In warm-humid climates, natural ventilation is very desirable. The building should, in such a case, have its longest dimension perpendicular to the direction of airflow. Further, the roof overhangs and pitch should be as high as possible. This would result in the maximum pressure difference and consequently maximum airflow. Level Thirteen: Fenestration Configuration

Effect of window position on light and ventilation. High windows act as ventilation points and also allow for the best distribution of light from overcast skies. Low windows do not allow much ventilation but allow an even distribution of ground reflected light. Middle windows allow for even ventilation but does not distribute the light as well. Light shelves allow for this.



Window shades for hot climates

Thumb rules for fenestration configuration

An ideal case fenestration positioning : Openings (windows), are placed on two external walls with the door on one internal wall. If air is incident on any of the external windows, then the fenestration configuration not only ensures a good distribution of air but also has a larger outlet area than inlet area. If the air is incident on any of the other walls then the door could act as the inlet into the room. Once again the outlet would be larger than the inlet and the configuration would allow good air distribution.



Effect of window location on indoor air motion The fenestration pattern and configuration involve the area, shape, location and relative positioning of

the windows. This would affect the air movement, daylight and glare indoors. If unshaded, the area would also affect radiative heat gain.

The location of the opening (defined by the sill and lintel levels) also affects ventilation. This is because temperature differences cause air to rise. Openings at higher levels, therefore, aid airflow. This is known as 'stack effect'.

The position of the opening affects the distribution of light indoors as it affects internal reflections. So equal size openings at the floor level, window level and ceiling level distribute the light differently.

Building Design In hot-dry climates windows need to be appropriately shaded. It is preferable if they are small in area. Airflow need not be encouraged since daytime air is hot. Due to low night temperatures natural ventilation may be desirable. Window sizes, if increased for this purpose, must be efficiently shaded from radiative heat gain. High openings or ventilators would be effective as heat vents. In warm-humid climates, fenestration areas should be large to facilitate ventilation. Large overhangs would be desirable in cutting off diffuse solar radiation. The fenestration height should be such that there is a good distribution of airflow over the human body. Lower sill levels might, therefore be preferable. The sill height of windows should be at low level between 0.5 to 0.7 m. Windows area should be 15 to 20 percent of floor area. Fixed windows should be avoided. Internal doorways between drawing & dining and dining to passage etc. may be left open without shutters/leaves. Ventilators should be provided as near to ceiling as possible. Provision of mechanical ventilation for circulation of fresh air as well as exhaust of used air should be made.



In cold climates fenestration should be large, unshaded but sealed. This would enable heat gain but reduce cool breezes. Fenestration location would be of little consequence. In cold climates heat loss through the window at night can be substantial. Window areas would be limited by this as well. Heat gain system like the trombe-wall and solar wall address just this issue. While they allow for heat gain during the day, heat loss at night is minimized. Glazing windows upto 25% floor area may be provided. Double glazing is preferable to avoid heat losses during winter nights. Window location makes a difference to the quality of light obtained indoors. High windows (ventilators) provide the best distribution of the direct and diffuse light. However, they also maximize the potential for glare and should have baffles. Low windows allow ground reflected light. Light being reflected from the ceiling provides the most uniform ventilation. The middle located window, in comparison, distributes neither sky light nor ground reflected light well. Some basic thumb rules can be followed, in the positioning of windows, to enhance air movement. Windows should be staggered rather than aligned (unless the incident wind is already at an angle). Partitions should not be placed near windows causing an abrupt change of wind direction. Similarly, windows on adjacent walls should preferably not be so placed as to cause an abrupt change of wind direction. It has been said earlier that indoor air speeds are greater if outlets are larger than inlets. It would be desirable to provide every room with windows on at least two walls. Each room would need to have a door, this should be on a third wall.



















