Passive Cooling Techniques to Improve Indoor Thermal Comfort of Modern Urban Houses in Hot-Humid Climate of INDIA Submitted By: PRABHAT CHHIROLYA Scholar Number: 141110016 Eighth Semester B. Arch.
Subject Coordinator: PROF ANUPAMA SHARMA
DEPARTMENT OF ARCHITECTURE AND PLANNING MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY, BHOPAL APRIL 2018
This dissertation, entitled “Passive Cooling Techniques to Improve Indoor Thermal Comfort of Modern Urban Houses in Hot-Humid Climate of INDIA” is being submitted in subject in ‘ARC 426, Research Principles and Dissertation’ as part of requirement for eighth semester of Bachelor of Architecture by the undersigned for evaluation. The matter embodied in this dissertation is compilation of others’ work, acknowledged properly. If, in future, it is found that the above statement is false, then the institute may take any action against me as per rules.
PRABHAT CHHIROLYA Scholar Number: 141110016 APRIL 2018
Knowledge is expression of experience gained in life. It is the choicest possession that should be happily shared with others. In this regard I feel great pleasure in submitting this dissertation on “Passive Cooling Techniques to Improve Indoor Thermal Comfort of Modern Urban Houses in Hot-Humid Climate of INDIA”. During this project I received a lot of help, advice and co-operation from our esteemed faculty and other distinguished persons. I wish to express my profound sense of gratitude to PROF ANUPAMA SHARMA. For their valuable guidance through the course of project without whose encouragement the project wouldn’t have been a success. I am grateful to my parents for their support and all those who have directly or indirectly helped me during the dissertation report.
PRABHAT CHHIROLYA (141110016.) B.ARCH VIII SEM APRIL 2018
Global climate change increases heat loads in urban areas causing health and productivity risks for millions of people. Air conditioning is growing rapidly .There has been a drastic increase in the use of air conditioning system for cooling the buildings all around the world. The last two decade has witnessed a severe energy crisis in developing countries especially during summer season primarily due to cooling load requirements of buildings. Increasing consumption of energy has led to environmental pollution resulting in global warming and ozone layer depletion. Passive cooling systems use non-mechanical methods to maintain a comfortable indoor temperature and are a key factor in mitigating the impact of buildings on the environment. Passive cooling techniques can reduce the peak cooling load in buildings, thus reducing the size of the air conditioning equipment and the period for which it is generally required. The aim of this study is to test the usefulness of applying selected passive cooling strategies to improve thermal performance and to reduce energy consumption of residential buildings in hot and humid climate and critically analyzes various passive cooling techniques and their role in providing thermalcomfort and its significance in energy conservation. The review in Chapter 2 focused on ventilative cooling. In particular, night ventilation is effective for buildings of high thermal mass and might be useful for modern houses. The review determined that due to climatic differences and lack of basic field data in hot humid climate, both basic and comprehensive studies would be required to assist application and development of passive cooling techniques for the region. and in this chapter I also focused types of passive cooling system in buildings and there importance and I also covered in Chapter 3 passive cooling techniques of vernacular houses in India and the effects of ventilative cooling in hot humid houses. The objectives were to understand the traditional passive cooling techniques and to evaluate their potential application to the hot humid houses. The review in Chapter 4 focused on classification of climates zone in India and describe the hot humid climate. And then I analyze some case studies from various climate zone and find measurement and techniques. compared the results related to the thermal performances of all the studied houses. For final conclusions, Chapter 7 summarized the main findings of this study and recommended key areas for further studies based on the limitations of this dissertation.
Keywords interior; Passive cooling technique; comfort; enegry; climate; hot&humid;
Contents Abstract .........................................................................................Error! Bookmark not defined. 1.INTRODDUCTION .................................................................................................................... 8 1.1 General Context .................................................................................................................... 8 1.1.1 Energy use in buildings ................................................................................................... 8 1.1.2 Energy-saving opportunities in buildings
1.1.3 Thermal adaptation of building occupants ......................................................................... 9
1.2 The study context and problem statement ............................................................................ 9 1.3 Research purpose ................................................................................................................ 12 2 PASSIVE COOLING IN BUILDINGS: A Literature Review â€“.............................................. 13 2.1 Fundamentals of passive cooling ............................................................................................. 13
2.1.1 Solar shading ................................................................................................................ 14 126.96.36.199 Shading by overhangs, louvers and awnings etc.. ................................................... 15 188.8.131.52 Shading of roof .................................................................................................... 15 184.108.40.206 Shading by trees and vegetation ............................................................................ 17 220.127.116.11 Shading by textured surfaces ................................................................................. 17 1.1.2 Insulation ..................................................................................................................... 18 1.1.3 Induced ventilation techniques ....................................................................................... 18 18.104.22.168 Solar chimney ...................................................................................................... 18 22.214.171.124 Air vents .............................................................................................................. 19 126.96.36.199 Wind tower .......................................................................................................... 20 2.1.4 Radiative cooling ........................................................................................................... 20 188.8.131.52 Diode roof ............................................................................................................ 21 184.108.40.206 Roof Pond ............................................................................................................ 21 2.1.5 Evaporative cooling ....................................................................................................... 21 220.127.116.11 Passive downdraft evaporative cooling (PDFC) ............................................... 21 18.104.22.168 Roof surface evaporative cooling (RSEC) ........................................................ 22 5
2.1.6 Earth coupling ............................................................................................................. 23 22.214.171.124 Earth air tunnel .................................................................................................. 23 126.96.36.199 Earth berming .................................................................................................... 23 2.1.7 Desiccant cooling ........................................................................................................ 24 3. Passive Cooling of Vernacular Buildings ................................................................................ 25 3.1 Indian Vernacular Architecture .......................................................................................... 28
3.1.1 Planning type ............................................................................................................. 28 3.1.2 Evaporative cooling and landscaping ........................................................................ 29 3.1.3 Radiative cooling and Courtyard planning ................................................................ 30 3.1.4 Ventilation and daylighting ........................................................................................ 32 3.1.5 Trombe wall ............................................................................................................... 34 3.1.6 Desiccant cooling ....................................................................................................... 34 4 CLIMATE CLASSIFICATION ................................................................................................ 36 5 CASE STUDYS ......................................................................................................................... 40 5.1 Introduction .................................................................................................................. 40 5.2 Case Study, Central University Of Rajesthan. Kishangarh, Ajmer, Rajasthan ............ .40 5.3 Case Study Of Suzlon One Earth Pune ......................................................................... 49 5.4 Centre For Environmental Science And Engineering Building at IIT.KANPUR ......... 50 6 SOLAR PASSIVE DESIGN FEATURES FOR WARM HUMID CLIMATE ...................... 53 6.1 Over view of passive concepts: ..................................................................................... 53 6.2 Landscape .................................................................................................................... 53 6.3 Building form ............................................................................................................... 55 6.4 Orirntation .................................................................................................................... 55 6.5 Shaded Evelope ........................................................................................................... 59 6.6 Daylight Integration ..................................................................................................... 67 6.7 Optimum WWR ........................................................................................................... 68 6.8 Advanced Passive Cooling .......................................................................................... 69 6.9 ECBC Envelope for Warm & Humid Climate ............................................................ 71 6.10 Wall ............................................................................................................................ 72
6.11 Window ....................................................................................................................... 74 6.12 Roof ............................................................................................................................. 82 6.13 Energy efficiency lighting .......................................................................................... 88 7 CONCLUSION ......................................................................................................................... 97 REFRENCES ............................................................................................................................ 97
Chapter 1 Introduction Modern societies are living on the Earthâ€™s resources at an increasingly rapid pace to satisfy certain needs and desires. In face of the present global climate change and related anthropogenic carbon emissions, the use of energy from fossil fuels becomes a main concern. At least three pathways to reduce energy consumption are at hand: first is to simply lower the demand and use less energy; second is to be more energy-efficient in our energy-based technology and systems; and third is to substitute fossil fuels with renewable energy sources to meet the demand. The same approaches apply to buildings. This thesis takes the first pathway as a fundamental approach towards energy-saving in buildings. Its focus is on passive cooling to fulfill indoor comfort needs.
1.1 General Context Changes in our climate system today in the form of global average surface temperature increase, global average sea level increase and snow cover decrease are understood to be driven more by human activities than natural processes. These drivers, including atmospheric concentrations of greenhouse gases and aerosols, land surface properties and solar radiation, individually alter the energy balance of the climate system by imposing either a warming effect or a cooling effect known as radiative forcing. 1.1.1 Energy Use in Buildings Buildings are known major energy consumers. Their operational energy is commonly supplied in the form of electricity which is generated from fossil fuels. Overall, studies reported that buildings energy use constitutes about one third of the global final energy use (Liu et al., 2010). By considering the development stage of respective regions, studies predict that buildings related CO2 emissions resulting from energy use will rise sharply in the coming two decades in developing nations, especially Developing Asia (Levine et al., 2007) (Figure 1.3). The increase will be driven by population growth, urbanization, increased and expanded wealth, and likely climate variability. Cooling demand in residential buildings in particular is highly sensitive to these factors (Liu et al., 2010; Sivak, 2009; Wong et al., 2012). It is likely to cause the increase at large as much of the developing world lies in the hot tropical belt.
Most of this growth is the result of increased electricity and natural gas use (because of greater access to these energy sources) and the increased use of appliances and energy-using equipment. Despite the rapid growth in buildings energy consumption. 1.1.2 Energy-Saving Opportunities in Buildings the buildings sector has the highest potential to mitigate carbon emissions; other sectors considered were energy supply, transport, industry, agriculture, forestry and waste. Approximately 29% reduction below the projected baseline of 2020 can be achieved in residential and commercial buildings at relatively low costs. To this end, measures aimed at operational energy saving in buildings are seen as the most diverse, largest and cost-effective mitigation opportunities. They fall into three categories: reducing the energy load; using efficient (active) systems to serve the load; and substituting renewable energy where possible (Liu et al., 2010). Since the load in buildings is usually ‘locked-in’ and dominated by space cooling or heating, reducing the load through climate-responsive passive techniques becomes imperative to achieve low-energy and lowcarbon buildings. Over the entire building stock, the largest portion of potential carbon and energy savings is in retrofitting existing buildings. This is due to the slow turnover of the stock, their conditions of being less energy efficient compared to new buildings and their potential to stimulate the sector’s change.
1.1.3 Thermal Adaptation of Building Occupants Human needs can be subjective matters. This is, in part, thanks to our ability to adjust ourselves to cope with prevailing circumstances. Recent studies showed that through thermal adaptation, our comfort temperature can vary with changing outdoor conditions, thus reducing indoor-outdoor temperature differences and required cooling loads of buildings. Energy-saving measures in the form of passive cooling techniques will enhance the adaptive capacity of buildings, which is necessary to support this kind of occupants’ adaptation .
1.2 The Study Context and Problem Statement EIA’s International Energy Outlook 2017 (IEO2017) projects that among all regions of the world, the fastest growth in buildings energy consumption through 2040 will occur in India. In the IEO2017 Reference case, delivered energy consumption for residential and commercial buildings in India is expected to increase by an average of 2.7% per year between 2015 and 2040, more than twice the global average increase. (figure 1.1)
China and India alone accounts for more than half of the worldâ€™s total increase in energy consumption over the 2015 to 2040 projection period.(figure2) Buildings energy consumption represented about 14% of total delivered energy consumption in India in 2015. Although EIA expects the rate of Indiaâ€™s commercial energy growth to be higher than its residential energy growth, the residential sector remains the greater consumer of buildings energy, representing more than 70% of the buildings buildings total throughout the projection period.
India is likely to witness a sharp jump in power consumption on account of rise in sales volume of air conditioner especially coastal areas. According to the US Energy Information Administration's (EIA) new "Today in Energy" brief, energy demand for space cooling is
growing rapidly in India and around the world, driven by rising incomes and a natural preference for certain ambient air temperatures. An early analysis of the program from Lawrence Berkeley National Laboratory (LBNL) estimated that the standards and labels would save 27 terawatthours of electricity use annually by 2020, nearly 14 per cent of projected electricity use for air conditioning in 2020.
Population of Heating / Cooling Appliances (millions) source
1.3 Research Purpose The main goal of this dessertation is to evaluate and propose application of passive cooling techniques to Improve Indoor Thermal Comfort in Hot-Humid Climate of INDIAWe work to reach this goal through the following objectives:
1. To examine the thermal adaptation of building occupants in hot-humid climate and to determine their thermal comfort requirements in naturally ventilated buildings. These thermal comfort requirements will serve dual functions, i.e. as the main assessment criteria to evaluate the performance of the passive cooling techniques studied in this work, and as an integral part of an energy-saving building standard to be proposed in the future.
2. To understand the existing situation of hot humid houses in two key aspects, i.e. current behavior related to cooling and energy consumption among households and effects of ventilate cooling on indoor thermal environments of existing houses.
3. To evaluate indoor thermal environments of vernacular houses and to find out their passive cooling techniques that can be useful for the terraced houses. Since climate has a major influence on thermal adaptation of occupants and also effectiveness of passive cooling techniques, it is most logical to firstly make scientific references to past local buildings. This aspect has not been addressed sufficiently in scientific research and thus field measurement is our main method.
4. To initiate a numerical model of a typical terraced house and to simulate selected passive cooling techniques to improve the indoor thermal comfort of the house. At this point, it is possible to begin employing computer simulations to provide feedback results that build on the field data. The basic questions, which passive cooling technique is effective and how well the passive cooling techniques work in urban climate compared to rural climate, are investigated.
Chapter 2 Passive Cooling of Buildings: A Literature Review This chapter provides a literature review of relevant studies of passive cooling in naturally ventilated buildings. We firstly explain some fundamental principles of passive cooling including use of terminologies. Since modern air conditioning was not available until its first introduction in 1902, we particularly look into studies of vernacular buildings in Section 2.2. Section 2.3 covers recent studies which dealt with ventilative cooling techniques. Two aspects of interest are: (1) current knowledge of their thermal performances, i.e. cooling effects that were achieved by applying certain cooling techniques; and (2) current methods used to develop the techniques. Finally, we consider the status of passive cooling developments in hot-humid climate from the review
2.1 Fundamentals of Passive Cooling The term ‘passive’ was adopted to describe space conditioning systems that are driven primarily by natural phenomena, i.e. without power driven mechanical devices. A ‘passive’ building may include the use of a low-energy fan or a pump when its application might enhance the performance. This is seen as a good opportunity in the study context of this work where the use of ceiling fans is very common in the indian houses. Cooling is the transfer of energy from the space or the air supplied to the space, in order to achieve a lower temperature and/or humidity level than those of the natural surroundings. Although the term ‘passive cooling’ is relatively new, its practice could be as old as time worldwide. From a wide viewpoint, it is inseparable from the concepts of bioclimatic design (Givoni, 1976; Hyde, 2008; Olgyay, 1963), tropical architecture (in the context of the tropics) (Bay and Ong, 2006; Koenigsberger et al., 1974; Lauber, 2005; Tzonis et al., 2001), ecohouse (Roaf, 2013) and green buildings (Bauer et al., 2010; Bonta and Snyder, 2008), whose aims include energy-saving and sustainability. Comprehensive references on passive cooling can be found in Cook (1989), Givoni (1994), Santamouris and Asimakopoulos (1996) and Santamouris (2007). In their generalities, these books focused on the climates of America, Israel, Europe and the Mediterranean climate (see Figure 2.3). Recent review apers (Givoni, 2011; Santamouris and Kolokotsa, 2013) which collated individual studies from a broader spectrum of climatic regions are also available. The above references are all in agreement that cooling strategies for buildings should be designed at three levels: (1) prevention of heat gains in the building; (2) modulation of heat gains; and (3) rejection of heat from the building to heat sinks by ventilation, evaporative cooling, radiative cooling or earth cooling. The natural heat sinks are the upper atmosphere (sky), the atmosphere (air) and the earth (ground and water). Examples of heat prevention strategies are use of microclimate and proper site design, building form and layout, shading, use of light colours or reflective surfaces on the exterior, use of insulated envelopes and control of
internal heat gains. Heat modulation is associated with high thermal mass materials, like brick and concrete, in building structures that act as a storage for heat during daytime and cold at night. It is considered to be useful for buildings in continuous occupation such as houses. Further, the role of heat rejection is to dissipate indoor heat to the heat sinks so that indoor temperature is possibly lower than the outdoors.
Figure 2.1. Modes of heat transfer to heat sinks in buildings. Source: Dimoudi, 1996.
The heat sinks and heat transfer mechanisms thus play an important role as cooling sources. This is the exact idea of passive cooling that differentiates it from bioclimatic design, which emphasizes the first level, although both are interrelated as mentioned above. In environments where cooling is required, the purpose is to increase heat losses from the body or to reduce the sensation of heat discomfort including discomfort resulting from skin wetness. 2.1.1 Solar shading Among all other solar passive cooling techniques solar shading is relevant to thermal cooling of buildings especially in a developing country owing to their cost effectiveness and easy to implement. Rural India and developing countries in Middle-east region has witnessed a steep rise masonry houses with RCC roofs. However the availability of electric power in the villages especially during summer is limited. These RCC roofs tend to make the indoor temperature very high around 41째C: This is due to high roof top temperature of around 65째C in arid regions. Solar shading with locally available materials like terracotta tiles, hay, inverted earthen pots, date palm branches etc. can reduce this temperature significantly. Shading with tree reduces ambient temperature near outer wall by 2째C to 2.5째C. On an average a depression of six degree 14
centigrade in room temperature has been observed when solar shading techniques are adopted. Kumar, Garg and Kaushik evaluated the performance of solar passive cooling techniques such as solar shading, insulation of building components and air exchange rate. In their study they found that a decrease in the indoor temperature by about 2.5째C to 4.5째C is noticed for solar shading. Results modified with insulation and controlled air exchange rate showed a further decrease of 4.4째C to 6.8째C in room temperature. The analysis suggested that solar shading is quite useful to development of passive cooling system to maintain indoor room air temperature lower than the conventional building without shade. 188.8.131.52 Shading by overhangs, louvers and awnings etc.. Well-designed sun control and shading devices, either as parts of a building or separately placed from a building facade, can dramatically reduce building peak heat gain and cooling requirements and improve the natural lighting quality of building interiors. The design of effective shading devices will depend on the solar orientation of a particular building facade. For example, simple fixed overhangs are very effective at shading south-facing windows in the summer when sun angles are high. However, the same horizontal device is ineffective at blocking low afternoon sun from entering westfacing windows during peak heat gain periods in the summer. Fig. 1 shows the different types of shading devices. 184.108.40.206 Shading of roof Shading the roof is a very important method of reducing heat gain. Roofs can be shaded by providing roof cover of concrete or plants or canvas or earthen pots etc. Shading provided by external means should not interfere with night-time cooling. A cover over the roof, made of concrete or galvanized iron sheets, provides protection from direct radiation. Disadvantage of this system is that it does not permit escaping of heat to the sky at night-time.
A cover of deciduous plants and creepers is a better alternative. Evaporation from the leaf surfaces brings down the temperature of the roof to a level than that of the daytime air temperature. At night, it is even lower than the sky temperature. 15
Covering of the entire surface area with the closely packed inverted earthen pots, as was being done in traditional buildings, increases the surface area for radiative emission. Insulating cover over the roof impedes heat flow into the building. However, it renders the roof unusable and maintenance difficult (Fig. 4). Broken china mosaic or ceramic tiles can also be used as top most layer in roof for reflection of incident radiation.
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. Fig. 5 shows the working principle of removable roof shades. Painting of the canvas white minimizes the radiative and conductive heat gain .
220.127.116.11 Shading by trees and vegetation Proper Landscaping can be one of the important factors for energy conservation in buildings. Vegetation and trees in particular, very effectively shade and reduce heat gain. Trees can be used with advantage to shade roof, walls and windows. Shading and evapotranspiration (the process by which a plant actively release water vapor) from trees can reduce surrounding air temperatures as much as 5Â°C. Different types of plants (trees, shrubs, vines) can be selected on the basis of their growth habit (tall, low, dense, light permeable) to provide the desired degree of shading for various window orientations and situations. The following points should be considered for summer shading : 1. Deciduous trees and shrubs provide summer shade yet allow winter access. The best locations for deciduous trees are on the south and southwest side of the building. When these trees drop their leaves in the winter, sunlight can reach inside to heat the interiors. 2. Trees with heavy foliage are very effective in obstructing the sunâ€™s rays and casting a dense shadow. Dense shade is cooler than filtered sunlight. High branching canopy trees can be used to shade the roof, walls and windows. 3. Evergreen trees on the south and west sides afford the best protection from the setting summer sun and cold winter winds. 4. Vertical shading is best for east and west walls and windows in summer, to protect from intense sun at low angles, e.g. screening by dense shrubs, trees, deciduous vines supported on a frame, shrubs used in combination with trees. 5. Shading and insulation for walls can be provided by plants that adhere to the wall, such as English ivy, or by plants supported by the wall, such as jasmine. 6. Horizontal shading is best for south-facing windows, e.g. deciduous vines (which lose foliage in the winter) such as ornamental grape or wisteria can be grown over a pergola for summer shading. 18.104.22.168 Shading by textured surfaces Surface shading can be provided as an integral part of the building element also. Highly textured walls have a portion of their surface in shade as shown in Figure 5. The increased surface area of such a wall results in an increased outer surface coefficient, which permits the sunlit surface to stay cooler as well as to cool down faster at night (Fig. 6).
2.1.2 Insulation The effect of insulation is to reduce heat gain and heat loss. The more insulation in a building exterior envelope, the less heat transferred into or out of the building due to temperature difference between the interior and exterior. Insulation also controls the interior mean radiant temperature (MRT) by isolating the interior surfaces from the influence of the exterior conditions, and also reduces draughts produced by temperature differences between walls and air. Insulation is of great value when a building requires mechanical heating or cooling and helps reduce the space-conditioning loads. Location of insulation and its optimum thickness are very important. In hot climates, insulation is placed on the outer face (facing exterior) of the wall or roof so that thermal mass of the wall is weakly coupled with the external source and strongly coupled with the interior. Use of 40 mm thick expanded polystyrene insulation on walls and vermiculite concrete insulation on the roof has brought down space-conditioning loads of the RETREAT building in Gurgaon by about 15% . Air cavities within walls or an attic space in the roof ceiling combination reduce the solar heat gain factor, thereby reducing spaceconditioning loads. The performance improves if the void is ventilated. Heat is transmitted through the air cavity by convection and radiation.
2.1.3 Induced ventilation techniques 22.214.171.124 Solar chimney A solar chimney is a modern device that induces natural ventilation by the thermal-buoyancy effect. The structure of the chimney absorbs solar energy during the day, thereby heating the enclosed air within and causing it to rise. Thus air is drawn from the building into an open near the bottom of the chimney. The air exhausted from the house, through the chimney, is replaced by ambient air. However, if the latter is warmer than the air inside the house, as it usually is during the day in hot climates, the continued use of the solar chimney will then begin to heat the structure of the building previously cooled overnight. The solar chimney is used to exhaust hot air from the building at a quick rate, thus improving the cooling potential of incoming air from other openings. Thus solar chimneys having a relatively low construction cost, can move air without the need for the expenditure of conventional forms of energy, and can help achieve
comfort by cooling the building structure at night. They can also improve the comfort of the inhabitants during the day if they are combined with an evaporative-cooling device. 126.96.36.199 Air vents Curved roofs and air vents are used in combination for passive cooling of air in hot and dry climates, where dusty winds make wind towers impracticable. Suited for single units, they work well in hot and dry and warm and humid climates. A hole in the apex of the domed or cylindrical roof with the protective cap over the vent directs the wind across it (Fig. 7). The opening at the top provides ventilation and provides an escape path for hot air collected at top. Arrangements may be made to draw air from the coolest part of the structure as replacement, to set up a continuous circulation and cool the living spaces. The system works on the principle of cooling by induced ventilation, caused by pressure differences.
Section showing detail of a wind tower. 188.8.131.52 Wind tower In a wind tower, the hot ambient air enters the tower through the openings in the tower, gets cooled, and thus becomes heavier and sinks down. The inlet and outlet of rooms induce cool air movement. When an inlet is provided to the rooms with an outlet on the other side, there is a draft of cool air. It resembles a chimney, with one end in the basement or lower floor and the other on the roof. The top part is divided into several vertical air spaces ending in the openings in the sides of the tower (Fig. 8). In the presence of wind, air is cooled more effectively and flows faster down the tower and into the living area. The system works effectively in hot and dry climates where diurnal variations are high. Figure 8 shows the section and detail of a wind tower.
2.1.4 Radiative cooling The roof of a building can be used both as a nocturnal radiator and also as a cold store. It is often a cost-effective solution. During the night the roof is exposed to the night sky, losing heat by longwave radiation and also by convection. During the day, the roof is externally insulated in
order to minimize the heat gains from solar radiation and the ambient air. The roof then absorbs the heat from the room below. 184.108.40.206 Diode roof The diode roof eliminates the water loss by evaporation and reduces heat gains without the need for movable insulation. It is a pipe system, consisting of a corrugated sheet-metal roof on which are placed polyethylene bags coated with white titanium oxide each containing a layer of pebbles wetted with water. The roof loses heat by long-wave heat radiation to the sky and by the evaporation of water which condenses on the inside surface of the bags and drops back onto the pebbles. By this means, it is possible to cool the roof to 4Â°C below the minimum air temperature . 220.127.116.11 Roof pond In this system a shallow water pond is provided over highly conductive flat roof with fixed side thermal insulation. The top thermal insulation is movable. The pond is covered in day hours to prevent heating of pond from solar radiation. The use of roof pond can lower room temperature by about 20Â°C. While keeping the pond open during night the water is cooled by nocturnal cooling. The covered pond during the day provides cooling due to the effect of nocturnally cooled water pond and on other side the thermal insulation cuts off the solar radiation from the roof. The system can be used for heating during the winter by operating the system just reverse. The movable insulation is taken away during day so the water of pond gets heated up by solar radiation and heating the building. The pond is covered in night to reduce the thermal losses from the roof and the hot water in the pond transfers heat into building .
2.1.5 Evaporative cooling Evaporative cooling is a passive cooling technique in which outdoor air is cooled by evaporating water before it is introduced in the building. Its physical principle lies in the fact that the heat of air is used to evaporate water, thus cooling the air, which in turn cools the living space in the building. However passive evaporative cooling can also be indirect. The roof can be cooled with a pond, wetted pads or spray, and the ceiling transformed into a cooling element that cools the space below by convection and radiation without raising the indoor humidity. 18.104.22.168 Passive downdraft evaporative cooling (PDEC) Passive downdraft evaporative cooling systems consist of a downdraft tower with wetted cellulose pads at the top of the tower. Water is distributed on the top of the pads, collected at the bottom into a sump and re-circulated by a pump. Certain designs exclude the re-circulation pump and use the pressure in the supply water line to periodically surge water over the pads, eliminating the requirement for any electrical energy input. In some designs, water is sprayed using micronisers or nozzles in place of pads, in others, water is made to drip. Thus, the towers 21
are equipped with evaporative cooling devices at the top to provide cool air by gravity flow. These towers are often described as reverse chimneys. While the column of warm air rises in a chimney, in this case the column of cool air falls. The air flow rate depends on the efficiency of the evaporative cooling device, tower height and cross section, as well as the resistance to air flow in the cooling device, tower and structure (if any) into which it discharges . Passive downdraft evaporative cooling tower has been used successfully at the Torrent Research Centre in Ahmedabad (Fig. 9). The inside temperatures of 29 –30 °C were recorded when the outside temperatures were 43 – 44 °C. Six to nine air changes per hour were achieved on different floors.
Passive Downdraught Evaporative Cooling in Torrent Research Centre, Ahmedabad. 22.214.171.124 Roof surface evaporative cooling (RSEC) In a tropical country like India, the solar radiation incident on roofs is very high in summer, leading to overheating of rooms below them. Roof surfaces can be effectively and inexpensively cooled by spraying water over suitable water-retentive materials (e.g., gunny bags) spread over the roof surface. Wetted roof surface provides the evaporation from the roof due to unsaturated ambient air. As the water evaporates, it draws most of the required latent heat from the surface, thus lowering its temperature of the roof and hence reduces heat gain. Therefore, the wetted roof temperatures 40°C are much lower than the ambient air about 55°C. However, the water requirement for such arrangement is very high and it is a main constrain in the arid region to adopt this technique .
2.1.6 Earth coupling This technique is used for passive cooling as well as heating of buildings, which is made possible by the earth acting as a massive heat sink. At depths beyond 4 to 5m, both daily and seasonal fluctuations die out and the soil temperature remains almost constant throughout the year. Thus, the underground or partially sunk buildings will provide both cooling (in summer) and heating (in winter) to the living space. A building may be coupled with the earth by burying it underground or berming. Figure 9 shows the functioning of earth berming during summer and winter . 126.96.36.199 Earth air tunnel The use of earth as a heat sink or a source for cooling/heating air in buried pipes or underground tunnels has been a testimony to Islamic and Persian architecture. The air passing through a tunnel or a buried pipe at a depth of few meters gets cooled in summers and heated in winters (Fig. 10). Parameters like surface area of pipe, length and depth of the tunnel below ground, dampness of the earth, humidity of inlet air velocity, affect the exchange of heat between air and the surrounding soil.
Working principle of earth air tunnel. 188.8.131.52 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. Fig. 11(a) and Fig. 11(b) shows the working principle of earth berming during summer and winter conditions.
Working principle of earth berming during summer (a) and winter (b) conditions.
2.1.7 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 personâ€™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 .
Chapter 3 Passive Cooling of Vernacular Buildings raditional buildings are time tested and well known for energy conservation. It therefore becomes necessary to understand and incorporate the passive technologies used in vernacular architecture in present day architecture since today's buildings are completely dependent on mechanical devices for heating/ cooling and providing comfortable indoor thermal conditions. It has been estimated that about 40 % of the world's energy is dedicated towards the building sector (Development 2009). Lifetime energy requirements of a building include the energy used in that building right from the construction stage to its occupancy and also include the energy that is necessary to sustain and maintain the building throughout its life which is dependent on selection of site, orientation of building, building material, shading devices, faรงade treatments, openings, windows, form and space utilization, courtyard planning, skylights, structure etc. Hence, incorporating these methods with passive solar techniques will help reduce the lifetime energy requirement of a building substantially. The combination of various passive heating and cooling techniques in order to achieve comfortable thermal temperature conditions has always been visible in vernacular architecture. Vernacular term refers to the construction done by the local people using traditional technologies, using locally available material in accordance with the environmental context. It offers a good solution to the climatic constraints. With incorporation of passive solar design, about 1-5 % of savings may be achieved without any additional cost in adaptation of such design (building orientation, shape, form, layout, size, aspect ratio, daylight and natural ventilation) (Mingfang 2002). Passive cooling refers to (a) reduction of solar heat gains by using solar shading devices, insulation, appropriate building materials and colors), (b) decrease in thermal heat gains by lighting controls etc., and (c) removal of excess heat from the building via convection, evaporative cooling, air movement, cool breeze, earth coupling, reflection of radiation etc. Passive cooling concepts channelize the air flow, thus removing the excess heat from the interior spaces. Therefore, lessons should be learnt from the vernacular architectural elements, before their demise and to create more appropriate and acceptable environment for present day users and sustainable development. Its applicability was already mapped in several studies Before the advent of mechanical refrigeration, ingenious use was made of the many means of cooling (e.g. damp cloths hung in draughts created by the connective stack effect in buildings). So dwellings and life styles were developed to make best possible use of these sources of cooling. The introduction of mechanical refrigeration permitted not only the ability to increase the likelihood of achieving complete thermal comfort for more extended periods, but also a great deal of flexibility in building design, and simultaneously led to changes in life style and work habits. However, increasingly, the use of a 'higher technology' resulted in natural-cooling techniques being ignored. Now with the growing realization of the rapid depletion of nonrenewable energy sources and of the adverse environmental impacts of fossil-fuel dissipating processes, it is accepted that it is foolish to continue consuming vast amounts of non-renewable fuels for the air-conditioning of buildings, when our ancestors achieved thermal comfort by natural means. Hence to reduce the emission of greenhouse gases, caused by fossil fuels to 25
power the cooling requirement of the buildings has stimulated the interest towards adoption of passive cooling techniques for buildings.
With combination of various passive cooling concepts as listed in in Table 1, energy saving potentials may be increased tremendously as summarized in Table 2.
3.1 Indian Vernacular Architecture Various passive cooling strategies have been discussed in Table 1 and 2. The following section comprises of few examples from the traditional Indian architecture and how these concepts have been implemented since long.
3.1.1 Planning type Indigenous planning layout was followed for places and simple small dwellings as seen in Shahjahanabad, Jaisalmer and many other cities in India. This type of a dense clustering layout ensured that the buildings were not exposed to the outer sun. This prevents the solar gain and the hot winds from entering the premises and also allows the cold wind to circulate within the building
3.1.2 Evaporative cooling and landscaping Concept of evaporative cooling is extensively used in ancient architecture for example Amber Fort, Rajasthan, India comprises of a garden which has been positioned just at the center of the lake to modify the microclimate for comfortable outdoor sitting during summers. Also, this concept can be seen in Red Fort, New Delhi where the entire building has been surrounded by water body and landscaping or by a water garden in Deegh Palace, Bharatpur, India or green area in Imambara, Lucknow (Figures 2a, 2b and 5). This was done in order to reduce the surrounding temperatures using landscaping. The small spaces were constructed to keep them sheltered from sun by the neighboring buildings. In case of large open spaces, plantation and water pools were used as landscaping element to protect them from the solar gains.
3.1.3 Radiative cooling and Courtyard planning Courtyard planning is visible in havelis and forts of Rajasthan, India for cooling effect (Figure 3). Courtyards were the main architectural element used in planning generally integrated with water bodies, vegetation and usually open to sky to enhance evaporative cooling, provision of shade and infuse maximum daylight in the buildings. In Shahjahanabad, India, the lower floors are used to spend the hot days while the nights are spent on the terrace taking advantage of the radiative cooling. The rooftops are sprinkled with water for evaporative cooling effect. Whereas during the winters, the days are spent on the sunny rooftops and the nights in the enclosed rooms. The buildings in Shahjahanabad, India were designed to allow the heavy cool air to enter the building. There was no provision of parapet wall towards the courtyard and solid parapets were constructed towards the street. Large openings are provided towards the courtyard to take advantage of radiative cooling so that the cool air is passed through the interiors.
Solar shading devices is another control medium for solar heat gains in form of horizontal (canopies, awnings, horizontal louvers, overhangs), vertical (vertical louvers, projecting fins), screening (movable insulations, vegetation etc.) or egg crate devices (jalis, grills). These devices reduce the heat gains and thus provides comfortable indoor temperature, reducing the cooling costs. They also act as an aesthetic element and also satisfy daylighting needs if properly designed. Mughal architecture used inclined and deep shades to cover more surface area with deep carvings which creates self-shading effect (Figures 4a and 4b). Horizontal shading devices are best suited for south oriented whereas vertical for east and west facing facades.
Ancient buildings were able to keep themselves cool without using the movable screens or curtains rather with the use of some passive techniques as seen in Diwan-e-Khas, Red Fort, Delhi, India (Figure 5). Two sets of columns spaced at 4 m have been placed. The provision of curtains and screens has been provided in these sets for use as per the need. During summers, three screens were used, out of which two were made of sprinkled grass to take advantage of the evaporative cooling. Whereas during winters, these screens were replaced by heavy quilted curtains. During the days, these curtains were rolled up to allow the sun to penetrate and were rolled down in the evening hours to retain the solar gain. These type of screens and curtains are also presently seen in Deegh Palace, Rajasthan, India. Roll up bamboo screens were also used in vernacular architecture as screening device for shading purposes and also for east and west orientations.
3.1.4 Ventilation and daylighting The details of the windows and the openings were also taken care of in the vernacular architecture. Examples included small windows (lesser than 100 mm in diameter) used in Amber fort, India in order to ensure the visibility without letting the light or air in (Figure 6a). Openings installed for ventilation purpose were seen in Shahjahanabad, India. These were installed near the floor level and near the roof level in order to let the cool air in from the bottom opening and let the hot air out from the top opening (Figs. 6b and 6c). At some places jalis (perforated stone or latticed screen) have been used to maintain privacy (Figures 4a, 6d and 6e), let the air and light enter the building and also allow the visual connectivity from inside to the outside surroundings (Figures 5d and 5e). Diffused light is allowed to enter the interiors during sunshine hours, and at the same time the interiors are not visible from the outside. For the outside view, small opening is provided at the eye level of the viewer in sitting position (Gupta 1984).
3.1.5 Trombe wall Another planning tool widely seen in vernacular architecture is thick walls i.e., Trombe walls (Figure 4a). They can be seen in Shahjahanabad, Jaisalmer, India. The natural, ventilated air also enters the chambers at the same temperature. The Trombe wall of 600 mm thickness is also seen in all the buildings of Banaras Hindu University, Varanasi. The inside temperature range was found to be about 25-28 Â°C when the outside temperature was in the range of about 45- 48 Â°C. (Gupta 1984). 2.7 Some examples of region specific architecture are: o Passive cooling features of vernacular architecture for Kerela, India have been discussed by Dili et al. (Dili, Naseer & Varghese 2010). These included courtyard planning, verandah, scale and proportions, orientation of the building, local building materials (mud, laterite, granite, lime mortar, wood, bamboo, clay roofing, coconut palm leaves etc.,) steep sloped roofs, 34
decorative jalis (for ventilation and daylight), strut comprising walls spaced by slats forming fenestration design thus creating comfortable indoor thermal conditions without input of an external cooling source. The temperature near the courtyards was found to be in the range of 3-8 ?C lower than the ambient with RH between 50- 80% (while the outside RH= 32-95 %) (Dili, Naseer & Varghese 2010) (Dili, Naseer & Varghese 2010). An example from Kerela of use of local materials like burnt coconut shells, egg whites, plant juices etc. is Padmanabhapuram palace, Kerela. Multiple courtyards are again seen in the palace to facilitate proper air movement. o Warli house, Maharashtra. These are mud plastered houses on framework of karvi walls. Suitable for hot humid climatic conditions. o Bhunga, Rajasthan. These are generally mud structures with thatch roof, circular in form planned around atriums or courtyards in clusters with minimum exposure to sun. These structures have controlled entry of light, wind and sun due to small openings. Suitable for hot dry climatic conditions. o Laterite structures, Goa. These are lime and earth structures with un-plastered sloping roof overhangs to battle sun and rain. Jackfruit wood is usually used as a local material eg. Chapel of Saint Catherine.
Chapter 4 CLIMATE CLASSIFICATION Diversity is one word that well defines India, be it culture, religious, ethnic, or geographical and climatic. The Koppen-Grieger classification  of climate types lists nine climatic zones in the country, ranging from hot and dry to warm and humid and cold and cloudy.The modified Koppen-Grieger classification developed by Peel and coworkers  divides the Indian subcontinent into eight major climatic zones (Figure 1), namely Am Tropical Monsoon; Aw Tropical Savannah; BSh Arid, Steppe, Hot; BWh Arid, Desert, Hot; Bwk Arid, Desert, Cold; Cwa Temperate, Dry Winter, Hot Summer; Cwb Temperate, Dry Winter, Warm Summer; Dsb Cold, Dry and Warm Summer.
a. Dwelling typology Using this climatic classification, the representative vernacular dwelling types in these zones have been classified in terms of their passive design elements (Table 1)â€”the construction, materials, orientation, and other specific design features. Table 1.
Dwelling type classification.
Chapter 5 CASE STUDY OF VARIOUS ECO BUILDINGS 5.1 INTRODUCTION Various buildings in India are being rated by LEEDS (India) & GRIHA rating system. Few buildings are being studied for in-depth analysis of various energy efficient features & sustainable building design points.
5.2 CASE STUDY, CENTRAL UNIVERSITY OF RAJASTHAN (CURAJ), KISHANGARH, AJMER, RAJASTHAN
Figure 1: View of The Central University, Rajasthan The Central University of Rajasthan established in 2009 and is located at Bander Sindri near Kishangarh on Jaipur -Ajmer Road . Itâ€™s campus is developed on green concepts particularly focused on water conservation, use of alternative sources of energy, solid waste management, vermin composting, green belt development, sustainable architectural designs of building etc. It
has emerged as a model campus giving a message that in a water scarce area the problem of water crisis can be handled & mitigating the impacts of regional as well as global environmental challenges to a greater extent.
5.2.1 Innovation and Design Process Central University of Rajasthan (CURAJ) has promoted ecological sustainability & recognized environmental responsibility as a way of life. Efforts to improve environmental sustainability comprise the establishment of the water-shed management, green buildings, sewage treatment plant, rain water harvesting, functional composting system (vermin composting), green belt development, installation of solar panels and solar water heaters etc. These campus sustainability efforts help to maintain the health of the public and surrounding ecosystems.
Figure 2: Layout Plan of Central University of Rajasthan Sustainable Sites
The buildings in CURAJ are designed in such a manner where energy conservation techniques & sustainable building techniques are implemented. Green buildings are necessary since there is a growing awareness on carbon emissions. It doesn’t take much to make a building green: utilize locally available material, make the best use of sunlight and natural air currents, harvest rainwater and recycle water, and manage waste efficiently. This was accomplished with the coordination of different organizations & sustainable techniques. Complying ECBC with cavity walls of 2” thickness having extruded polystyrene insulation + roof slab with 3” polyurethane insulation to reduce heat gain - windows protected from direct solar exposure with the help of horizontal shading devices & precast vertical ‘Jalis’’ a vernacular design feature of this region.
Figure 3: Courtyards at Central University of Rajasthan Essential area of window glass is fitted with high performance glazing. Local stone is used for external cladding. In the master plan, much emphasizes is given on courtyards / enclosed spaces , cutouts in student’s hostels, passive systems like. earth air tunnel, geothermal heat exchange and two stage evaporative cooling. The existing Building Thermal Performance was recorded on 30.05.2013 and was found to be:
5.2.2 Water Efficiency Rain Water Harvesting: The rain water harvesting is carried out by collecting and storing rain water from roof tops and land surface. The principal components consist of the catchment area, conveyance system and collection device. The quantity of rainfall in Rajasthan being minimal, rainwater pipes for roof drainage are installed in the range of 75mm to 100 mm diameter.
Figure 4: Rain Water Harvesting at Central University, Rajasthan Series of ponds have been constructed under the integrated rain water harvesting scheme. The total area covered is 217 ha. The total catchment is divided into 7 parts having area of 11 ha, 15 ha, 8.5 ha, 2.5 ha, 18 ha, 56 ha, 42 ha and 64 ha. Water gets collected into ponds. There are eight buildings which are equipped with water harvesting and sewer re-charge system, provide water into 30 bores raising the groundwater table to support the green cover. Two artificial water bodies on either side of the campus have 20 crore litres of water. Rare birds like egret, black nirds, ibis, heron and lapwing are now regular visiters to these ponds. These surrounding ponds are helping in maintaining the favorable microclimate of the university.
5.2.3 Energy and Atmosphere Solar Power: Availability of sunshine for a larger part of the day makes it convenient to use solar energy to meet most of its own & in a first-of-its-kind initiative, meets 60% of its energy needs through solar energy. The university has successfully channelized solar energy to meet its daily requirement. The university campus has four buildings with a monthly requirement of 600 kilowatt electricity (for November 2013), of which 420 KW is generated by solar panels. The energy is used to heat around 80,000 litersâ€™ of water and light up 62 electric poles in the campus. In addition to being eco friendly, the method is also proving to be cost effective for the university. It is now also planning to install four solar units of 30 KW each and one of 1 megawatt in the next year to run 100% on a renewable source of energy. The university lies in the tropical region and receives enough sunlight to meet 100% energy requirements for eight months barring months of monsoon and winter. Fulfilling its commitment of promoting â€˜sustainable developmentâ€™, the university has installed 62 electric poles of 400 watt each across the university driven by solar panels. These poles automatically become active after sunset and switch off automatically during sunrise. Throughout the day the cells recharge themselves to a level that they could run for 16 hours. Fans, tube lights, computers and other equipments below 9 KW can be operated by solar energy. The production of solar energy in future will attain self reliance in terms of power requirement. In addition to being a renewable source of energy and eco friendly, the method is also proving to be cost effective for the university. University is now planning to install four solar units of 30 KW each and one of 1 MW in order to run 100% on a renewable source of energy.
Figure 5: Solar Street Lights at Central University, Rajasthan 45
Sewage Treatment Plant: The sewage treatment plant treats University wastewater. A 120 KLD Sewage Treatment Plant based on Sequential Batch Reactor (SBR) Technology has been installed and the treated water is used for the irrigation of plants with drip technology to reduce water loss. The water is also supplied to the nursery plants. The main benefit of wastewater treatment is maintaining clean water for reuse. Wastewater treatment processes remove potential disease-causing contaminants through a filtering system that blocks their path and further treatment that kills harmful organisms. This keeps potential diseases and bacteria from entering other water sources, or the ground, and harming people as well as plants and animals.
Figure 6: Sewage Treatment Plant at Central University, Rajasthan
5.2.4 Materials and Resources Sustainability and environmental considerations have been taken care during construction practices .Few examples are the use of fly ash bricks and smart usage of materials on-site for construction. Energy usage is optimized by keeping the temperature within the buildings at an optimal range by using double layered glass panes for windows, and passive subterranean cooling system coupled with thermal insulation on the roof of the buildings. The architectural style is a fusion of traditional Rajasthani architectural styles and features and contemporary design elements. The chhatri and jaali are used as prominent design elements in the buildings giving the buildings the look of a unique blend of the traditional and the modern.
5.2.5 Indoor Environmental Quality Vermin composting: They have established the Solid Waste Management Facility using Vermincompost technology at its campus to manage the solid waste generated on the campus. The earthworms vermin-compost is proving to be highly nutritive ‘organic fertilizer’ and more powerful ‘growth promoter’ over the conventional composts and a ‘protective’ farm input (increasing the physical, chemical & biological properties of soil, restoring & improving its natural fertility) against the ‘destructive’ chemical fertilizers which have destroyed the soil properties and decreased its natural fertility over the years. Vermin-compost is rich in NKP (nitrogen, potassium and phosphorus), micronutrients, and beneficial soil microbes and also contain ‘plant growth hormones and enzymes’. Vermin-compost is produced from waste materials collected in dustbin which is converted into a ‘valuable resource’. More significant is that it is of biological origin i.e. a ‘renewable resource’ and will be readily available to mankind in future.
Figure 7: Vermin composting at Central University, Rajasthan
Nursery: Plants are natureâ€™s one of the most beautiful wonders. A nursery has been created for the students to do the research work and also it greatly reduces the personâ€™s stress levels. Natural aesthetic beauty is soothing to people, and keeping ornamental flowers around the university buildings is an excellent way to reduce levels of stress and anxiety. As a result of the positive energy they derive from the environment, the chances of suffering from stress-related depression will decrease as well. Green Transport: Students of various departments are asked to make use of cycles instead of any other two/ three or four wheeler making it a pollution free environment
5.3 CASE STUDY- SUZLON ONE EARTH, PUNE One Earth is Suzlonâ€™s corporate headquarters office in Pune, India. The building, showcases itself as a building project with minimal impact on the environment. The complex consists of an office block and a corporate learning centre. The buildings are positioned on a site area of 45 392 sq.m. The total built-up area is 70 865 sq.m. The building is certified green under GRIHA rating system. There are various salient features which enable it to become an iconic green building.
5.3.1 Architectural aspects: The architectural aspects of design are well taken care of in the building. Passive design strategies help in ensuring that visual and thermal comfort is maintained within the building with minimum interventions of technologies. The orientation of the blocks is such that the majority of the buildingâ€™s facades face north, south, north-west and south-east. This enables adequate day lighting and glare control. Glazing on the first and second floors has been shaded from direct solar radiation using louvers. These also act as important design elements of the building and give it a visual identity. Architectural design of the office block is such that various extrusions on various floors shade portions of the building. Therefore, the building is partly self-shaded. In order to create an interesting office atmosphere, break-out spaces have been created in the form of small terraces which have been interspersed all over the office block. In order to minimize disturbance on site and to ensure easy maintenance, various utility corridors have been provided coupled with the roads and pathways on site. This ensures minimum site disruption postoccupancy.
5.3.2 Energy conservation: High efficiency mechanical systems in the building ensure that the energy consumption of the building is significantly reduced. All desks are equipped with LED lights for task lighting which are governed by motion sensors. So they turn on only when people are seated on their seats. This reduces lighting load to 0.8 W/sq.ft. Extremely high efficiency HVAC systems have been chosen. The HVAC system has various components like pre-cooling of fresh air heat recovery/ exchanger mechanisms to minimize energy consumption in HVAC. Overall, the complex has managed to reduce its energy consumption by 47% below the GRIHA criterion..
5.3.3 Renewable energy: After the reduction of energy performance index of the building , renewable energy systems in the form of solar PV and windmills were installed to generate approximately 250 000 units of electricity through renewable sources annually. The project has an installed 13.44 kWp of solar PV and 18 windmills with power capacity of 4.75 kW each.
5.3.4 Water conservation: 49
Drastic steps have been taken in order to reduce its water consumption. Use of low flow fixtures throughout the complex ensures that the building requires 65% less water than conventional buildings for sanitary purposes. By planting only native trees and shrubs and using high efficiency sprinkler and drip irrigation systems, the complex has reduced its landscape water requirement by about 50%. Over 55% of the water in the building is recycled and reused within the complex.
5.3.5 Low energy materials: The intent of making a green building is also reflected in various materials used in the structural systems and in interiors. Use of Post Tension slabs help in reducing concrete requirement in slabs and beams by 37%. Use of PT structural system has helped reduce the requirement of structural steel by almost 50%. Use of Siporex blocks gives the walls of the buildings good insulation while simultaneously using waste material like fly-ash. Majority of the materials used for interior application have high recycled content and are low-energy materials.
5.3.6 Observations: Overall, the One Earth complex has adopted very high standards for energy and water management. The One Earth complex has taken strong steps to minimize its environmental impact at various levels while simultaneously projecting a very contemporary feel to the buildings and spaces, thereby proving the point that green buildings can be as aesthetically pleasing as any conventional building and yet are able to have minimal negative impact on environment.
5.4 CASE STUDY- CENTRE FOR ENVIRONMENTAL SCIENCE AND ENGINEERING BUILDING (CESE) AT IIT, KANPUR Centre for Environmental Science and Engineering Building at IIT, Kanpur has been taken as an example to study how the building attempted various GRIHA criteria to make it into a green building.
5.4.1 Sustainable site planning In order to minimize impact of site development on the environment and surroundings, several best practice guidelines were adopted like demarcation of site for construction, installation dust screen around the disturbed area to prevent air pollution and spillage to undisturbed site area. Top soil was excavated, stored and preserved outside the disturbed construction site. Erosion control systems were adopted and several trees on site were protected. To increase the perviousness of site and to reduce heat island effect caused due to hard paving around the building, total paving around the building was restricted to 17%, and more than 50% of the paving is either pervious or shaded by trees. 50
5.4.2 Water conservation In this building, reduction in landscape water demand by more than 50% was achieved by use of minimum grass/lawn area, maximum green area under native vegetation and native trees. Low flow plumbing fixtures are used in the building resulting in reduced water consumption from GRIHAâ€™s benchmark in this building by 62%. Waste water is treated and reused for irrigation. Rain water harvesting has been done.
5.4.3Conservation and efficient utilization of resources: energy Maximum points /weight age in GRIHA is given for energy conservation. The criteria and commitment for energy conservation could be divided into three parts. a. Energy: end use b. Energy: embodied and construction c. Energy: Renewable energy utilization Energy: end use Annual energy consumption of the building has been reduced through following measures: 1. Architectural design optimized as per the climate of Kanpur, sun path analysis, predominant wind direction, and existing vegetation. 2. Optimized building envelope to comply to the Energy Conservation Building. Code, to reduce cooling load in the air conditioned spaces and to achieve thermal comfort in the non air conditioned areas. 3. Efficient window design by selecting efficient glazing, external shading to reduce solar heat gain but at the same time achieving glare free natural daylight inside all the laboratory spaces of the building. 4. Roof shaded by bamboo trellis and green cover to reduce external solar heat gains from the roof. 5. Common circulation areas are natural day lit and naturally ventilated through integration of skylights and ventilators. 6. Water cooled chiller selected that complies with the efficiency as per ECBC. 7. Variable Frequency Drive installed in the Air Handling Units (AHUs). 8. Low energy strategies such as replacement of water cooler by water body to cool the condenser water loop, integration of thermal energy storage and earth air tunnels enabled reduction in chiller capacity. 9. Energy efficient lighting design that complies to ECBC. 10. Integration of daylight with artificial lighting.
11. Optimized architectural design and integration of energy efficient fixtures resulted in the reduction of annual energy consumption by 41% from GRIHAâ€™s benchmark.
Energy: embodied and construction GRIHA encourages replacement of high energy intensive materials with low energy intensive materials, to utilize regionally available materials, materials which use low energy in their manufacturing process. Following few were the measures incorporated: 1. Portland pozzolona cement (PPC) with fly-ash content is used in plaster and masonry mortar. 2. Wood for doors is procured from commercially managed forests. Modular furniture made from particle board is used for interiors. Energy: renewable energy utilization Following measures incorporated to integrate renewable sources of energy with the building: 1. Renewable energy from photovoltaic panels provide annual energy r
Chapter 6 SOLAR PASSIVE DESIGN FEATURES FOR WARM & HUMID CLIMATE 6.1 Over view of passive concepts: Incorporation of solar passive techniques in a building design helps to minimize load on conventional systems such as heating, cooling, ventilation & light. Passive strategies provide thermal and visual comfort by using natural energy sources & sinks. Ex: solar radiation, outside air, wet surfaces, vegetation etc means, in warm & humid climate: an architectâ€˜s aim would be to design a building in such a way that solar gains are maximized in winter and, reduce solar gains in summer, and maximize natural ventilation. Once the solar passive architectural concepts are applied to design, the load on conventional systems (HVAC & lighting) is reduced. Architects can achieve a solar passive design by studying the macro and micro climate of the site, applying bioclimatic architecture design features and taking advantage of the existing natural resources on the site. The solar passive design strategy should vary from one climate to another. Since these buildings can also function independent of mechanical systems, in case of power failure they are still well lit by natural daylight and thermally comfortable.
6.2 Landscape Landscaping is an important element in altering the micro-climate of a place. Proper landscaping reduced direct sun from striking and heating up building surfaces. It is the best way to provide a buffer for heat, sun, noise, traffic, and airflow or for diverting airflow or exchanging heat in a solar-passive design. It prevents reflected light carrying heat into a building from the ground or other surfaces. Additionally, the shade created by trees, reduces air temperature of the micro climate around the building through evapo-transpiration. Properly designed roof gardens help to reduce heat loads in a building.
Figure 2: Location of landscape to cut direct sunlight and shade buildings (source: www.oikos.com ) Deciduous trees provide shade in summers and sunlight in winters; hence, planting such trees on the west and southwestern side of the building is a natural solar passive strategy. On the other hand, evergreen trees on the north and north-west of the building provide shade round the year. The use of dense trees and shrub plantings on the west and southwest sides of a building will block the summer setting sun.
Figure 3: Dense trees and shrub plantings blocks the summer setting sun (source: www.bloomsoon.com , www.landscape-design-advisor.com) Natural cooling without air-conditioning can be enhanced by locating trees to channel southeasterly summer breezes in tropical climates like India. Cooling breezes will be able to pass through the trunks of trees placed for shading. Shade can also be created by using a combination of landscape features, such as shrubs and vines on arbours or trellises. Trees, which serve as windbreaks or form shelterbelts, diminish wind. Certain climbers are also useful for shading exposed walls from direct sunlight. Trees also provide visual relief and a psychological barrier from traffic and thus reduce pollution on the site. Place trees approximately half the width of the treeâ€˜s canopy from the building and spaced at 1/4th to 1/3rd the canopy width. This parameter should also be considered for good daylight integration inside the built spaces.
Figure 4: Location of trees to protect from winds (source: the dailygreen.com) 54
6.3 Building form Building form can affect solar access and wind exposure as well as the rate of heat loss or heat gain through the external envelope. The volume of space inside a building that needs to be heated or cooled and its relationship with the area of the envelope enclosing the volume affect the thermal performance of the building. Building form can affect solar access and wind exposure as well as the rate of heat loss or heat gain through the external envelope. The general design objectives are
Contain the exposure of external elements by means of compact building envelope and careful consideration of the treatment of different elevations Use sheltering and buffering Compactness: The building form also determines the air flow pattern around the building directly affecting its ventilation. The compactness of the building is measured using the ratio of surface area to volume (S/V). The depth of a building also determines the requirement for artificial lighting. The greater the depth, higher is the need for artificial lighting. The circular geometry has the lowest S/V ratio thus the conduction gains from the building envelope as well as solar gains from windows are least, in circular geometry in comparison to other building geometries which is most energy efficient in warm & humid climate.
Sheltering or self-shading Built form, which is designed such that it is self-shaded through massing or articulation results in sheltered built forms, and cuts off a large amount of direct solar radiation. In warm & humid climate, the envelope should be designed so that it remains shaded for the greater part of the day; the external walls should be so planned that they shade each other.
6.4 ORIENTATION In solar passive design features, orientation is a major design consideration, mainly with regard to solar radiation, daylight and wind.
In tropical climate like India long facades of buildings oriented towards Northâ€”South are preferred. East and West receive maximum solar radiation during summer. In predominantly cold regions, also North South long facades are advisable, as South orientation receives maximum intensity of solar radiation in winter months. Orientation in warm & humid climate: Orient the buildings with the long axes in the east-west direction so that the longest walls face north and south, and only the short wall face east and west.
Figure5: Orientation with longer facades on N-S The below figures shows the solar radiation received on each facade of the building orientation which were modelled in Eco-tect software. South orientation receives maximum solar radiation during winters which is preferable. East and West receive maximum solar radiation during summer. West is a crucial orientation because high intensity of solar radiation is received during
summers, when the internal gains are also at its peak. Thus, designers need to be very careful while designing West facade and spaces behind West facade. Orientation also plays an important role with respect to wind direction. At building level, orientation affects the heat gain through building envelope and thus the cooling demand, orientation may affect the daylight factor depending upon the surrounding built forms, and finally the depending upon the windward and leeward orientation fenestration could be designed to integrate natural ventilation. Table 1: Average solar radiation intensity on various facades of a building in warm & humid climate
Figure 6: Average daily solar radiation received on North orientation in Bhubaneswar
Figure 7: Average daily solar radiation received on South orientation in Bhubaneswar
Figure 8: Average daily solar radiation received on East orientation in Bhubaneswar
Figure 9: Average daily solar radiation received on West orientation in Bhubaneswar
6.5 SHADED ENVELOPE All the elements of a building are vulnerable to heat gains. Proper shading is therefore a very important aspect in solar passive building design. It is observed using software simulations that, shading of roof, walls and windows have considerable potential in reducing the cooling energy consumption. This section explains the technical details and advantages of shaded envelope (Roof, Walls and Windows) Shading of roof: Shading of roof through design features like pergolas or solar photovoltaic panels helps in reducing the incident direct solar radiation on the roof surface. This in turn helps to reduce the air temperature of the roof and conduction gains in the space below. It is observed using software simulations that shading of roof has equal potential in reducing the cooling energy consumption to that of an insulated roof. For ex: the below figure 1 shows the fully shaded roof of Centre for Environment, IIT Kanpur through Pergolas and Solar PV panels.
Figure 11 Fully shaded roof of Research lab in IIT, Kanpur through pergolas & Solar PV panels 59
Impact of shaded roof It is observed in air conditioned buildings, adopting ECBC envelope in building has high energy saving potential. However, shaded roof has similar energy saving potential as that of ECBC compliant roof. Shading of roof could can be done by designing pergolas, trellis on roof or by installation of solar panels. Why the shading of roof is required? Roof receives a significant amount of solar radiation round the year. As illustrated in Fig below, the intensity of solar radiation received is maximum on the horizontal plane which is the roof. Conductance of heat from the roof can be very high if not insulated well. This can result in increased cooling load if the space below is air conditioned or high discomfort hours if the space below is naturally ventilated.
Figure 12: Average Solar radiation received on a roof Cool Roof: Along with shading of roof, solar passive design also recommends cool roof. Cool roofs are roofs covered with a reflective coating that has high emissivity property which is very effective in reflecting the sunâ€˜s energy away from the roof surface. This quality greatly helps in reducing the cooling load that needs to be met by the HVAC system. Combination of insulated roof with cool roof has high saving energy potential. Shading of windows: Heat gain through window is determined by the overall heat loss co-efficient U-value (W/m2 -k) and solar energy gain factor, and is much higher as compared to that through opaque wall. Direct sunlight can cause glare. Incorporation of shading elements with windows help in: keeping out the sunâ€˜s heat, block uncomfortable direct sun, and soften harsh daylight contrasts. Shading 60
devices are therefore necessary to allow glare free natural light. Shading devices are also critical for visual and thermal comfort and for minimizing mechanical cooling loads. Shading devices for windows and walls moderate heat gains into the building. External shading is the most effective ways of shading, as it cuts off direct sunlight during summer and allows winter sunlight to enter inside the space. However, in cloudy weather or if not designed properly, these can reduce daylight availability inside the space. For such cases, external moving shading devices are preferred. External shading devices should be designed according to the orientation of faรงade. For instance on North orientation minimum or no shading is required. On South orientation external shades should be designed after studying the sun path. Shading devices on South orientation could be permanent in nature, as most part of the day, Sun remains in South orientation. It is preferable to design movable external shading devices on East and West facades, so that the shades could be removed after sun faces opposite orientation.
Figure 13 External shading for windows as an effective means of shading
Horizontal Sun Angle (HSA) This is the horizontal angle between the normal of the window and the Sun azimuth angle at a given time The horizontal sun angle at critical hours can be cut by the vertical fins provided as external shading device. 61
Vertical Solar Angle (VSA) It is the angle that a plane containing the bottom two points of the window and the centre of the Sun makes with the ground when measured normal to the shaded surface The vertical solar angle at critical hours can be cut by the horizontal fins provided as external shading device.
Figure 15 Horizontal fins as an external shading device
Figure21: Fixed types of louvers (www.wbdg.org) Movable louvers:
They can cope well with the sunâ€˜s changing altitude and can also be adjusted as per the angle of sunâ€˜s altitude, but can be very costly and also requires high operation and maintenance.
Figure 22: Adjustable and Movable types of louvers (www. fsec.ucf.edu)
Shading of walls: Shading walls from direct sun can be one of the simplest and most effective ways of reducing the heat load on a building. Clever use of shade can dramatically improve the comfort conditions inside and reduce reliance on expensive air conditioning systems. As in the warm & humid climate, the East and West facades receive maximum solar intensity especially in summers, shading the East and West facades is a challenge. As eastern and western walls heat significantly in summers, overhangs may not be enough. The entire east and west walls have to be shaded to protect from the strong summer solar intensity.
Figure 23: Shading of East & West wall through green wall feature Impact of shaded wall: In day time use buildings shaded east and west walls have higher energy saving potential than insulating the external walls. The different kinds of shadings for wall are explained below: Deep porches and verandas - These are excellent at reducing the solar heat gain in a building because they completely shade the walls. They also cut the solar intensity creating cool spaces even without plants or shrubs.
Figure 24: Shading of through deep porches and verandahs Sun-proof fabric covers:
For porches, or sails these can be attached to the building itself, and are a good seasonal solution. It is possible to get fabrics and shade cloth that cut out more than 95% of sunlight, and have guarantees of 20 years minimum lifespan. These are put up at the start of the shading season, taken down at the end. In addition to their function of blocking sunlight, fabric sails can be visually exciting. A row of triangular sails, for example, tilted so they overlap each other, and provides excellent shade and visual interest.
Figure 25: Shading through sun proof fabric and verandahs (Source: www.infolink.com ) Vertical shading: Vertical shading is the most advisable form of shading to cut the intensive solar heat gains for east and west walls especially in summer. It is some form of vertical light blocker that is placed at the external edge of the overhang or porch roof, extending all the way to the ground. It can be movable louvers, jalis, panels of trellis, lath or shade cloth or it can be climbing plants trained to grow up supports, either deciduous or rapidly growing annual vines. Plants have an additional cooling advantage: as well as blocking light, they evaporate cool air passing through their leaves. Jalis act as cost effective treatments for shading both for windows and walls. They bring coolness due to the breezes blowing through the jalis that fill walls. Gaps between the jalis let air and sunlight through a wall, while diffusing the glare of sunlight and cutting the intense heat. They also act as elements for enhancing and beautifying the architecture of the building. The modern form of shading is solar PV shading. In this, the solar energy can be used simultaneously shading the building. Vertical shading has the advantage that is can be placed close to a wall, so is especially useful where deep porches are not wanted and/or not possible due to lack of space.
Figure 27: Solar PV panels as shading modules for the walls (Source: www.sunenergysite.eu ) Figure 28: Series of louvers as a wall shading device (Source: www.fsec.ucf.edu )
Figure 31: Fixed types of jalis for shading (www.wikipedia.org)
6.6 DAYLIGHT INTEGRATION Day lighting has a major effect on the appearance of space and can have considerable implications on energy efficiency, if used properly. Its variability is subtly pleasing to the occupant in contrast to the relatively monotonous environment produced by artificial light. It helps to create optimum working conditions by bringing out the natural contrast and colour of objects. The presence of natural light can bring a sense of well being and awareness of the wider environment. Day lighting is important particularly in commercial and other non-domestic buildings that function during the day. Integration of day lighting with artificial light brings about considerable savings in energy consumption. A good day lighting system, has number of elements most of which must be incorporated into the building design at an early stage. This can be achieved by considering the following relation to the incidence of day light on the building. • Orientation, space organization and geometry of the space to be lit • Location, form & dimension of the fenestrations through which day light will enter • Location & surface properties of internal partitions that affect the day light distribution by reflection • Location, form and dimensions of shading devices that provides protection from excessive light and glare • Light and thermal characteristics of the glazing materials Innovative Day lighting systems: Day lighting systems help in better daylight integration in the buildings. There are various day lighting systems. Some of them are as explained below: Light pipes: Light tubes or light pipes are used for transporting or distributing natural or artificial light. In their application of day lighting, they are also called as sun pipes, solar pipes, solar light pipes, or day light pipes. Generally, it may refer to “a tube or pipe for transport of light to another location, minimizing the loss of light.” They make it possible to transport daylight through thick roof structures and attics. They are easier to install in retrofit applications than skylights. For practical reasons, light pipes are limited to smaller light collection areas. If the building has an attic, installing skylights in the roof requires building a reflective enclosure to pass the light through the attic. Unless the attic is empty, this may be difficult. Light pipes are easier to pass through attics. In effect, a light pipe is a small skylight with an integral reflective enclosure.
The light pipe has to be made of a solid transparent material, such as glass or plastic. The light pipe can be long, and it can have any number of bends. To make economical, all the light has to be squeezed in to a light piece of small diameter. A small conduit is desirable to minimise heat loss and to make the light pipe easy to install.
There are 2 types of light pipes: 1. Simple light pipes: (rigid wall light pipe & flexible wall light pipe as shown in figures below) 2. Sun trackers 1. Simple light pipes: The pipe may be rigid or flexible. Flexible light pipes are easier to install but they suffer more light loss from increased reflection and scatter inside the pipe 2.Sun trackers: A movable mirror or refracting system can be used to align the incoming sunlight with the axis of the pipe, minimizing reflecting losses which is called as ―sun trackerǁ
Figure 34: Rigid & flexible wall light pipe (source: www.reliant.com ) Figure 35: sun tracker (source:www.reuk.co.uk )
6.7 OPTIMUM WWR Window Wall Ratio (WWR)- Window Wall Ratio is the ratio of vertical fenestration area to gross exterior wall area. Gross exterior wall area is measured horizontally from the exterior surface; it is measured vertically from the top of the floor to the bottom of the roof. Example – The wall shown in the figure has width ‗W‘ and height ‗H‘. The window height is ‗a‘ and width is ‗b‘ as shown in figure. The WWR for the given facade will be = (a x b)/(H x W)
6.8 ADVANCED PASSIVE COOLING Passive cooling systems rely on natural heat-sinks to remove heat from the building. They derive cooling directly from evaporation, convection, and radiation without using any intermediate electrical devices. All passive cooling strategies rely on daily changes in temperature and relative humidity. The applicability of each system depends on the climatic conditions. The relatively simple techniques that can be adopted to provide natural cooling in the building through solar passive design strategies have been explained earlier. This section briefly describes the various passive techniques that aim heat loss from the building by convection, radiation and evaporation, or by using storage capacity of surrounding, eg: earth berming Ventilation: Good natural ventilation requires locating openings in opposite pressure zones. Natural ventilation can also be enhanced through tall spaces like stacks, chimneys etc in a building. With openings near the top of stacks warm air can escape where as cooler air enters the building from openings near the ground. (Source: Energy efficient buildings in India, TERI).
Wind tower: In a wind tower, the hot air enters the tower through the openings in the tower gets cooled, and this become heavier and sinks down. The inlet and outlet of rooms induce cool air movement. In the presence of wind, air is cooled more effectively and flows faster down the tower and into the living area. After a whole day of air exchanges, the tower becomes warm in the evenings. During the night, cooler ambient air comes in contact with the bottom of the tower through the rooms. The tower wall absorbs heat during daytime and releases it at night, warming the cool night air in the tower. Warm air moves up, creating an upward draft, and draws cool night air through the doors and windows into the building. In
dense urban areas, the wind tower has to be long enough to be able to catch enough air. Also protection from driving rain is difficult. (Source: Energy efficient buildings in India, TERI).
Courtyard effects - Due to incident solar radiation in a courtyard, the air gets warmer and rises. Cool air from the ground level flows through the louvered openings of rooms surrounding a courtyard, thus producing air flows. At night, the warm roof surfaces get cooled by convection and radiation. If this heat exchange reduces roof surface temperature to wet bulb temperature of air, condensation of atmosphere moisture occurs on the roof and the gain due to condensation limits further cooling. If the roof surfaces are sloped towards the internal courtyard, the cooled air sinks into the court and enters the living space through low-level openings, gets warmed up, and then leaves the room through high-level openings. However, care should be taken that the courtyard does not receive intense solar radiation, which would lead to conduction and radiation heat gains into the building. (Source: Energy efficient buildings in India, TERI)
Earth air tunnels: Daily and annual temperature fluctuation decreases with the increase in depth below the ground surface. At a depth of about 4m below ground, the temperature inside the earth remains nearly constant round the year and is nearly equal to the annual average temperature of the place. A tunnel in the form of a pipe or otherwise embedded at a depth of about 4m below the ground will acquire the same temperature as the surrounding earth at its surface and therefore the ambient air ventilated through this tunnel will get cooled in summer and warmed in winter and this air can be used for cooling in summer and heating in winter. (Source: Energy efficient buildings in India, TERI)
(Source: Sustainable habitat at Gual pahari, TERI)
6.9 ECBC Envelope for Warm & Humid Climate The building envelope refers to the exterior faĂ§ade, and is comprised of opaque components and fenestration systems. Opaque components include walls, roofs, slabs on grade (in touch with ground), basement walls, and opaque doors. Fenestration systems include windows, skylights, ventilators, and doors that are more than one-half glazed. The envelope protects the buildingâ€˜s interiors and occupants from the weather conditions and shields them from other external factors e.g: noise, pollution, etc
Envelope design strongly affects the visual and thermal comfort of the occupants, as well as energy consumption in the building. The design of the building envelope is generally responsible of the architect. The building designer is responsible for making sure that the building envelope is energy-efficient and complies with the mandatory and prescriptive requirements of the code. A well designed building envelope not only helps in complying with the Energy Conservation Building Envelope (ECBC) but can also result in first cost savings by taking advantage of daylighting and correct HVAC sizing. The building envelope and its components are key determinants of the amount of heat gain and loss and wind that enters inside. The envelope protects the buildingâ€˜s interior and occupants from the weather conditions and other external elements. The design features of the envelope strongly affect the visual and thermal comfort of the occupants, as well as energy consumption in the building mentioned below are explained further The commonly considered elements of ECBC envelope are: 1. Walls 2. window 3. Roof
6.10 Wall Walls are a major part of the building. Envelope receives large amounts of solar radiation. The heat storage capacity and heat conduction property of walls are key to meeting desired thermal comfort conditions. The wall thickness, materials and finishes can be chosen based on the heating and cooling needs of the building. Appropriate thermal insulation and air cavities in walls reduce heat transmission into building which is the primary aim in a hot region. The basic elements of the Wall system are: 1. Exterior cladding (natural or synthetic) 2. Drainage plane (s) 3. Air barrier system(s) 4. Vapour Retarder (s) 5. Insulating Element(s) 6. Structural elements 72
Thermal storage / thermal capacity: Thermal capacity is the measure of the amount of energy required to raise the temperature of a layer of material, it is a product of density multiplied by specific heat and volume of the construction layer. The main effect of heat storage within the building structure is to moderate fluctuation in the indoor temperature. In a building system, we can understand thermal mass as the ability of a building material to store heat energy to balance the fluctuations in the heat energy requirements or room temperature in the building due to varying outside air temperature. The capacity to store heat depends upon the mass and therefore on the density of the material as well as on its specific heat capacity. Thus, high density materials such as concrete, bricks, stone are said to have high thermal mass owing to their high capacity to store heat while lightweight materials such as wood, or plastics have low thermal mass. The heat storing capacity of the building materials help achieve thermal comfort conditions by providing a time delay. This thermal storage effect increases with increasing compactness, density and specific heat capacity of materials. Thermal performance of walls can be improved by following ways: 1. Increasing wall thickness 2. Providing air cavity between walls and hollow masonry blocks 3. Applying insulation on the external surface. 4. Applying light coloured distemper on the exposed side of the wall. Conductance: Conductivity (K) is defined as the rate of heat flow through a unit area of unit thickness of the material, by a unit temperature difference between the two sides. The unit is W/mK (Watt per metre - degree Kelvin). The conductivity value varies from 0.03 W/mK for insulators to 400W/mK for metals. Materials with lower conductivity are preferred, as they are better insulators and would reduce the external heat gains from the envelope. Walls-insulation: Thermal insulation is of great value when a building requires mechanical heating or cooling insulation helps reduce the spaceconditioning loads. Location of insulation and its optimum thickness are important. In hot climate, insulation is placed on the outer face (facing exterior)
of the wall so that thermal mass of the wall is likely coupled with the external source and strongly coupled with the interior (Bansal, Hauser, Minke 1994). Air Cavities: Air cavities within walls or an attic space in the roof-ceiling combination reduce the solar heat gain factor, thereby reducing space-conditioning loads. The performance improves of the void is ventilated. Heat is transmitted through the air cavity by convection and radiation. A cavity represents a resistance, which is not proportional to its thickness. For a thickness >20mm, the resistance to heat flow remains nearly constant. Ventilated air does not reduce radiative heat transfer from roof to ceiling. The radiative component of heat transfer may be reduced by using low emissivity or high reflective coating (E.g.: aluminum foil) on either surface facing the cavity. With aluminium foil attached to the top of ceiling, the resistance for downward heat flow increases to about 0.4m2k/W, compared to 0.21m2 k/M in the absence of the foil (Bansal, Hauser, Minke, 1994).
6.11 Window Windows are very important component of the building envelope, in addition to providing physical and visual connection to outside; it also allows heat and light in and adds beauty to the building. Solar radiation coming in through windows provides natural lighting, natural air and heat gain to the space inside, thus significantly impacting the energy usage of the building. The main purpose of a building and its windows is to provide thermal and visual comfort to the occupants and if this can be achieved using less energy, so much the better. Proper location, sizing, and detailing of windows and shading form are important part of the bioclimatic design as they help to keep the sun and wind out of building or allow them when needed. The location of openings for ventilation is determined by prevalent wind direction, openings at higher levels naturally aid in venting out hot air. Size, Shape and orientation of openings moderate air velocity and flow in the room, a small inlet and a large outlet increase the velocity and distribution of air flow through the room. When possible, the house should be so positioned as the site that it takes advantage of prevailing winds. The prevailing wind direction is from the south/south-east during summer. The recommendation is IS: 3362-1977 code of practices for the design if windows for lightly and ventilation. There should be sufficient air motion in hot-humid and warm-humid climates. In such areas, fans are essential to provide comfortable air motion indoors, fenestrations having 15% -20% of floor area are found adequate for both ventilation & day lighting in hot & dry, and hot & humid regions. Natural light is also admitted into a building through glazed openings. Thus, fenestrations design is primarily governed by requirements of heat gain and losses, ventilation and day lighting. The important components of a window are the glazing systems and shading devices. 74
Shading Devices (source: www.is.jnit.edu ) Primary components of a window which have significant impact on energy and cost of the building for which guidelines are provided in this section are as follows: 1. Window size, placement 2. Glazing 3. Frame 4. Shading (external & internal) Window size & placement: Height of window head: The higher the window head, the deeper will be the penetration of daylight. Sill height (height from floor to the bottom of the window): The optimum sill for good illumination as well for good ventilation should be between the illumination workspace and head level of a person. Carrying out any task, the suitable work plane levels are to be 1.0 to 0.3 m high respectively
Strip windows provide more uniform daylight Punched windows should be paired with work areas to avoid creating contrasts of light and dark areas. Avoid big windows close to task areas since they can be source of thermal discomfort.
Also larger the windows, the more important glazing selection and shading effectiveness are to control glare and heat gain. Use separate apertures for view and daylight—for good day lighting and glare control separate the view and light windows. Light window should have clear glass for maximum daylight penetration. Tinted glass could be used below for glare control. The structure in between the two provides a visual break and an opportunity to attach light shelf or shading device. 1. Glazing systems: The most commonly glazing material used in openings is glass, although recently polycarbonate sheets are being used for skylights. Before recent innovations in glass, films and coatings, a typical residential window with one or two layers of glazing allowed roughly 75% -85% of the solar energy to enter a building. Internal shading devices such as curtains, or blinds could reflect back some of that energy outside the building. The weak thermal characteristics of the windows became a prime target for research and development. In an attempt to control the indoor air temperature of buildings windows admit direct solar radiation and hence promote heat gain. This is desirable in cold climates, but is critical in hot climates. The window size should be kept minimum in hot &dry regions. The primary properties of glazing that impact energy are
Visible reflectance (affecting heat and light reflection) Thermal transmittance or U - value (affecting conduction heat gains) Solar heat gain (affecting direct solar gain) Spectral selectivity (affecting daylight and heat gain) Glazing colour (affects the thermal and visual properties of glazing systems and thus energy usage)
Visible transmittance (VLT %) or daylight transmittance
This is the percentage of normally incident visible light transmitted through the glazing. Glazing with a high visible transmittance is clearer in appearance and provide sufficient daylight and views. Clear glass however, can create glare problem. Glazing with low visible transmittance give better glare control, but offer minimal daylight integration and diminished views. Visible reflectance or daylight reflectance This is the percentage of incident light that is reflected back. Most manufacturers provide both outside reflectance (exterior daytime view) and inside reflectance (interior mirror image at night). Treatments such as metallic coating increase the reflectance. Reflective glazing reflects a large portion of the solar radiation incident on it, thereby restricting heat gain inside the building, which is advantageous. Disadvantage is these reflective glazing allows low visible transmittance and thus minimal daylight integration. An ideal spectrally selective glazing admits only the part of the sunâ€™s energy that is useful for day lighting
Table 7: Typical optical and thermal properties for high-performance glazing options Solar heat gain coefficient (SHGC or shading coefficient) These are the indicators of total solar heat gain through a glazing. SHGC is the ratio of the solar heat gain entering the space through the fenestration area to the incident solar radiation. Solar heat gains include directly transmitted solar heat and absorbed solar radiation, which is then re radiated, conducted or convected into the space. These indices are dimensionless numbers between 0 and 1 that indicate the total heat transfer of the sunâ€˜s radiation. These properties are widely used in cooling load calculations. Glass with a lower SHGC or SC (Shading coefficient) helps in reducing cooling loads in hot climate zones.
However, glass with a low SHGC also usually has low VLT. Hence use of glass with spectral selectivity is recommended for day use air conditioned buildings to enhance day lighting and reduce cooling loads. In air conditioned buildings, it is mandatory to achieve SHGC lower or equal to that recommended by ECBC for various window wall ratios.
Glazing types and materials: Until recently, single pane clear glass was the primary glazing material used in windows. The past few decades have seen immense changes in glazing technology. Several types of advanced glazing systems are available to help control heat loss or gain. The advanced glazing include double and triple pane windows with coatings such as low - e (low emissivity)/ spectrally selective, heat absorbing (tinted), or reflective, gas filled windows and windows based on combination of these options.
Substantial improvements in glazing performance are expected from new materials and techniques. The creation of vacuum or partial vacuum in the cavity of a double glazed unit and the use of Aerogel to fill the cavity can lower the U-value considerably. Air space between glass layers Thermal resistance provided by the air cavity between glass layers increases with increase in cavity width upto 12mm. Convection currents, which form in wider cavities, lead to a drop in thermal resistance
Fig 7: Single glazing window Fig 8: Double glazing window (Source: www.green-planetsolarenergy.com )
Fig 8: Glazing materials (Source: www.gmpartitions.net ) Insulated glazing units
Insulating glazing units are hermetically sealed, multiple pane assembles consisting of two or more glazing layers held and bonded at their perimeter by a space bar typically containing a desiccant material. The glazing used in IGUs could be clear, tinted or coated or reflective as mentioned above. The spacer serves to separate the panes of glass and to provide a surface for primary and secondary sealant adhesion, since heat transfer at the edge of the IGU is greater than its centre. The choice of material for spacer is critical to the IGUs performance. It is advisable to use SS, galvanized steel, polymers or foamed silicon which have lower conductivities than aluminium. The hermetically sealed space between glass panes is most often filled with air, argon and krypton being two other alternatives. Latest trends in glazing systems a) Switchable glazing : Switchable glazing will enable the user to change the optical or thermal properties of sealed glazed units. The most useful and potentially applicable switchable property is the chromogenic phenomenon in which materials change their reflectivity and absorptivity. Examples of chromogenic proceeese are: thermochromic, electrochromic and photochromic materials. Thermochromic glazing changes optical properties in response to temperature changes. It consists of mainly liquids or gels sandwitched between layers of glazing. Thermochromic windows are designed to block solar gain. A drawback is that they reduce visible light transmission as well. Electrochromic glazing changes optical properties when an electric current goes through the unit. A thin mettalic film is deposited on the glass similar to low emissivity coatings. Another technique involves sandwiching a liquid quartz film between two layers of glazing. Photochromic materials change their properties in response to light. Photo gray sunglasses are best example. When photochromic materials change their transmittance, the absorptivity is increased, thus causing glass to absorb more heat. On sunny, colds days, they absorb solar heat and room source heat and then radiate some heat back to the surroundings. On sunny, hot days, they do not reject as much solar heat as reflective glass. b) Evacuated glazing : Evacuated, sealed insulated glazing is designed to achieve higher levels of thermal performance by using a vacuum to inhibit any kind conductive or convective heat losses. Flip windows for improved performance in summers and winters. The double pane absorptive glazing system for hot climates has a useful feature for regions of warm & humid climate, having both heating and cooling seasons If the positions of the two glass panes are flipped over from their summertime positions during the cold winter, the system converts to a solar radiant heater. In the cold day position, solar radiation passes through the clear outer pane is absorbed by the inner pane, which heats up and then this heat is transmitted to the inside, warming the building. The low - e coating on the inner
pane now reduces the radiation of heat from this hot inner pane to the cold outer one, trapping the heat inside. Flipping it back over makes it a hot climate glazing system since the solar heat is now absorbed in the outer pane of glass, which is insulated from the interior of the building. Frame The type and quality of window frame affects a window‘s air infiltration and heat gain / heat loss characteristics. There are three kinds of framing material mostly used which are metal, wood and polymers.
Wood has a good structural integrity and insulating values but low resistance to external weather conditions. Metal frames have poor thermal performance, but have excellent structural characteristics and durability. Aluminium is the most preferred metal for frames, but it is highly conductive and its thermal performance can be improved with a thermal break (a non metal component which separates the metal frame exposed to the outside from surfaces exposed to the inside.) Vinyl window frames which are primarily made from polyvinyl chloride (PVC) offer many advantages. Available in wide range of style and shapes PVC frames has high R– value (Resistance value) and low maintenance.
Solar control glazing: They are very effective against heat flow across the window but can reduce transmission of light inside the space
Fig 10: solar control glazing
The function of light shelf is to protect the occupants from direct sunlight in summer and allow sufficient light in winter. The light shelf is placed above the eye level so that reflections do not get into eyes of occupants. Uniform daylight is also The light shelf should be sufficiently projected outside so as to protect the window. The angle of the light shelf is also important as tilting helps in deeper light penetration but also reflects light back. The finishes should be reflective as matte surface reflects back about half light backwards The top of the shelf should be matte white or diffusely specular, and not visible from any point in the room.
Fig 11: Modelling of Light shelves
6.12 Roof Conventional Roof Insulation Practices - In India Roof Insulation with conventional materials like Foam Concrete, Mud Faska, Brick Bat Coba has been practiced since ages. However these products are quite heavy and add dead load to the roof slab. Moreover the thermal conductivity value is very high which results into higher thickness application without much benefit. These products have the tendency to develop cracks and as a result water absorption takes place. Moreover, the products are open cell and porous type which results into water absorption. This application also calls for good workmanship. 82
What types of roofing products are available? Products for low-slope roofs, found on commercial and industrial buildings fall into two categories: single-ply materials and coatings. Single-ply materials are large sheets of pre-made roofing that are mechanically fastened over the existing roof and sealed at the seams. Coatings are applied using rollers, sprays, or brushes, over an existing clean, leak-free roof surface. Products for sloped roofs are currently available in clay, or concrete tiles. These products stay cooler by the use of special pigments that reflect the sunâ€˜s infrared heat. In India, lime coats, white tiles grouted with white cement, special paints, etc. are used as cool roofing materials. Energy efficient roof insulations: The roof requires significant solar radiation and plays an important role in heat gain/losses, day lighting and ventilation. Depending on the climatic needs, proper roof treatment is essential. In a hot region, the roof should have enough insulating properties to minimize heat gains. A few roof protection methods are as follows: A cover of decidous plants or creepers can be provided. Evaporation from roof surfaces will keep the rooms cool. The entire roof surface can be covered with inverted earthen pots. It is also an insulated cover of still air over the roof shading device. This can be mounted close to the roof in the day and can be rolled to permit radiative cooling at night. The upper surfaces of the canvas should be painted white to minimize the radiation absorbed by the canvas and consequent conductive heat gain through it Effective roof insulation can be provided by using vermiculite concrete. Heat gains through roofs can be reduced by adopting the following techniques. Green roof concept A roofing system through shading, insulation, evapotranspiration and thermal mass, thus reducing a buildingâ€˜s energy demands for space conditioning. The green roof moderates the heat flow through the roofing system and helps in reducing the temperature fluctuations due to changing outside environment. Green roof is a roof of a building
that is partially or completely covered with vegetation and soil that is planted over waterproofing membrane. If widely used green roofs can also reduce the problem of urban heat island which would further reduce the energy consumption in urban areas. Use of high reflective material on roof top Use light coloured roofs having an SRI (solar reflectance index) of 50% or more. The dark coloured, traditional roofing finishes have SRI varying from 5 - 20%. A good example of high SRI is the use of broken china mosaic and light coloured tiles as roof finish, which reflects heat off the surface because of high solar reflectivity and infrared emittance, which prevents heat gain and thus help in reducing the cooling load from the building envelope. If the roof is exposed to Solar heat it will input continuous heat inside the building which in turn will add to the A.C. machinery load. This concept of protecting the roof is termed as Roof Insulation. There are many different types of insulation materials to choose from when applying on a commercial roof or reproofing an existing structure The function of roof insulation is to insulate the building against heat in flow from outside during the day. Use of higher albedo materials/cool roof: Higher albedo materials can significantly reduce the heat island effect. Higher the albedo larger will be the amount of solar radiation reflected back to the sky. Roofs provided with high reflective coatings remains cooler than those with low reflectance surfaces and are known as cool roofs. Cool roofs can reduce the building heat gain and can save the summertime air conditioning expenditures. These paints are highly efficient, energy-saving, flexible coatings, made from water-based pure acrylic resin system filled with vacuumed sodium borosilicate ceramic micro spheres of less than 100 microns in size. Each micro sphere acts as a sealed cell and entire mastic acts as a thermally efficient blanket covering the entire structure. These coatings are non-toxic, friendly to the environment, and form a monolithic (seamless) membrane that bridges hairline cracks. They are completely washable and resist many harsh chemicals. Roof Coats have high reflectance and high remittance as well as a very low conductivity value. They offer UV protection and low VOC's. They display excellent dirt pick-up resistance and retain their flexibility after aging. These roof Coats reduce noise transmission and have an effective use range from -40 Deg C (-40 Deg F) to 375 Deg C (700 Deg F) Thermal insulation for roof:
Well insulated roof with the insulation placed on the external side is an effective measure to reduce solar heat gains from the roof top. The insulated materials should be well protected by water proofing. For air conditioned spaces, Energy Conservation Building Code (ECBC) recommends the thermal performance for external roof for all the five climate zones in India. Over deck Insulation In this system a thermal barrier or insulation is provided over the RCC, so that the heat of the sun is not allowed to reach the RCC slab of the roof at all. In this way we can preserve the RCC from getting heated up Once the RCC is heated up there is no other way for the heat to escape other than inside the building So ever though the thermal barrier is provided under the RCC, as in underdeck insulation, some heat passes through it and heats up the ambience of the room. This decreases the comfort level of the room and if the building is centrally AC, increases the AC load Hence we can safely conclude that overdeck insulation has its own advantages over underdeck insulation. Overdeck Insulation material should have adequate compression resistance, low water absorption, resistance to high ambient temp. and low thermal conductivity. Overdeck insulation applications are carried out by either – • Preformed insulation materials • In-situ application A) Preformed insulation material : Preformed Insulation material are further classified as under :
Expanded Polystyrene slabs Extruded Polystyrene slab Polyurethane / Polyisocyanurate slabs
Perlite boads Expanded polystyrene (EPS, Thermocol)- is a light weight cellular plastic foam material composed of carbon and hydrogen atoms. It is derived from petroleum and natural gas by products. Molded EPS does not involve the use of CFCs. Polystyrene is highly economical EPS meets most of the performance Extruded Polystrene - Extruded Polystyrene is an improvement of Expanded Polystyrene material. This material is also comprise of beads / globules which are 85
compressed to form slabs and pipesections. Incase of Extruded Polystyrene the beads are very closely linked to each other so that the material become rigid and there is no air gap between the beads. It is a close cells material and a skin is formed on the top which stops water absorption Polyisocyanurate / Polyurethane foam slab – These are urethane foam insulation materials having low thermal conductivity, low smoke emission & low water absorption. The product confirms to IS:12436 & BS 5608. Perlite – Perlite insulation is an organic rigid board insulation. It is composed of expanded volcanic glass and wood fibres bonded with asphaltic binders. This makes a rigid board light in weight, dimensionally stable and good in compressive strength. In western countries at one time perlite was most common insulation material used for roof insulation. Although still popular, its low ‗R‘ value, high ‗K‘ value and tendency to absorb moisture have lessened its popularity.
The application procedure for overdeck insulation featuring preformed insulants are
Cleaning of the roof surface to be free of dirt and loose particles Providing a primer and adhesive coat Adhering of insulation with adhesive, taking care to seal all the joints between insulation also with a sealant. •Providing a protective plaster layer with reinforcement Providing an elastomeric membrane or felt type waterproofing treatment on top.
Insitu Technology (i)
Spray applied Polyurethane: Unlike preformed materials, this is applied directly over the roof by spraying. This eliminates separate fixing procedure. It is formed spontaneously when Isocyanate and Polyol are mixed in the presence of a blowing agent to create close cell homogenous jointless insulation cover of the roof. It is designed to combine highly efficient thermal insulation with great ease of application It is ideal for a wide range of insulation application particularly for roofs and walls of the building. By nature liquid applied foam polyurethane adheres 86
strongly to almost any surface regardless of form. The seamless and monolithic nature of spray foam provides a full proof method of sealing cracks and rendering any surface moisture resistance and drought proof. The excellent adhesion of the sprayed material makes mechanical fastening redundant. The comparatively low density of material adds little weight to overall loading. Besides external use, sprayed foam can be applied internally as well. (The foam can also be sprayed on the under side of roofs and suspended floors and on inner surface of walls). Insulation The first set of mandatory requirements addresses the proper installation and protection of insulation materials. It is recommended that insulation materials be installed according to the manufacturer‘s recommendations and in a manner that will achieve the rated insulation R-value. Compressing the insulation reduces the effective R-value and the thermal performance of the construction assembly.
Cool Roof: Depending on the material and construction, a roof will have different properties that determine how it conducts heat to the inside of the building. ―Cool roofsǁ are roofs covered with a reflective coating that has a high emissivity property that is very effective in reflecting the sun‘s energy away from the roof surface. These ―cool roofsǁ are known to stay 10°C to 16°C cooler than a normal roof under a hot summer sun; this quality greatly reduces heat gain inside the building and the cooling load that needs to be met by the HVAC system. Box below discusses how solar heat radiation is reflected, absorbed and emitted from the roof and how these concepts are used in developing cool roofs. Reflectance, Absorptance, and Emissivity - The heat transfer process involved in the roof, is similar to the heat transfer that takes in a wall. Heat transfer across the roof is more prominent compared to the wall because of higher incidence of solar radiation. Depending on the properties of the roof material and construction, the roof reflects part of the solar radiation back to the environment, and absorbs the other part of the heat in the roof (See Figure 4.9). Finally, portion of the absorbed heat in the roof is emitted as longwave radiation back to the environment and the remaining part of the absorbed heat is conducted inside of the building. This heat transfer process is governed by the Solar Reflectance and Emissivity (Thermal Emittance) properties of the roof material, apart from the thermal conductivity of the materials used in the roof.
Heat Transfer Through Roof
6.13 Energy efficiency lighting Any lighting scheme interior or exterior can be called an efficient scheme when it provides the required illuminance level for the application it has been designed while utilizing least amount of energy. Technical information for achieving efficiency in the lighting scheme for three categories which are External Lighting, Internal Lighting for Commercial Buildings, and Internal Lighting for Residential Buildings have been elaborated below Optimized Lighting Scheme – What is an optimized lighting scheme? Optimized lighting scheme comprises of two key components – 1. Effectiveness of the lighting scheme 2. Efficiency of the lighting scheme 1. Effectiveness of lighting scheme Effective Lighting Scheme – A lighting scheme can be called an effective one when it serves the purpose for which it is designed. The purpose of a lighting scheme is to provide visual comfort for different kind of activities in different spaces as per various standards. In India we have standard for visual comfort given in Part 8, Section-1, Table - 4 of Lighting and Ventilation of NBC (National Building Code of India) 2005 and a lighting scheme will be called effective if it conforms to NBC 2005 recommended illuminance levels for various activities and spaces Efficient Lighting scheme –
A lighting scheme is called efficient over the other when for the same visual comfort and usage pattern it will consume lesser amount of electrical energy. The efficiency in a lighting scheme is guided by the following three factors – a. Lighting Power Density b. Integration of artificial lighting scheme with daylight c. Lighting controls a. Lighting Power Density – Lighting power density of a lighting scheme is the ratio of installed lighting power in a space (includes power of lamp, ballast, current regulators and control devices) to the floor area of that space. The ECBC (Energy Conservation Building Code of India) 2007 gives the maximum permissible lighting power values for different types of space usages and the lighting power of a designed scheme should be lower than or equal to these values. b. Energy efficiency in external lighting – External lighting in and around a building is used for lighting pedestrian walks, landscaping, artifacts, parkways & parking, facade lighting, security etc. To achieve the efficiency in external lighting scheme designed for various application following can be practiced – Use of efficient Lamps –Depending upon the kind of application, the following lamp types can be used in external lighting scheme to improve the efficiency High Pressure Sodium Vapour Lamps (HPSV) High Pressure Sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. The efficacy of HPSV varies from 50 -140 lumens/watt and lamp life is around 16000 -24000 hrs. The color rendering index of these lamps is quite low. These lamps can be primarily used for applications where lighting from a height around 5m is desired such as for the drive ways in a campus or car parking etc. Metal Halide Lamps (MH) Metal halide lamps are similar in construction and appearance to mercury vapor lamps. The addition of metal halide gases to mercury gas within the lamp results in higher light output, more lumens per watt (50-110 lumen/watt) and a higher color rendition index than from mercury gas alone. Metal halide lamps have shorter lifetimes (5,000–20,000 hours) compared to both mercury vapor and highpressure sodium lamps. Metal halide lamps in external lighting are used when better color
rendition is required such as facade lighting etc. Fluorescent Lamps Fluorescent lamp is a lowâ€“pressure mercury electric discharge lamp with a glass tube filled with a mixture of argon gas and mercury vapour at low pressure. When current flows through the ionized gas between the electrodes, it emits ultraviolet (UV) radiation from the mercury arc which is then converted to visible light by a fluorescent coating on the inside of the tube. Fluorescent lamps are usually available in various colors i.e. warm white, normal white, cool white etc. Fluorescent lamp efficacy is around 40-100 lumen/watt and the average life of the lamp varies from 10000 â€“ 24000 hrs. The color rendering of the fluorescent lamps is very good. Compact Fluorescent lamps (CFL) Compact fluorescent lamps are fluorescent lamps which are small in size, come in both types ballast integrated and non-integrated. Life of CFL lamps is almost 9 to 10 times to that of an incandescent lamp. CFLs can be extensively used in landscape lighting, security lighting fixtures, bollard lighting etc. Light emitting diode (LED) Lamps The LEDs are semiconductor lighting sources. When a diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. LEDs consume very less power and have a very long life (50000-70000 hrs) as they are shock and vibration proof. LEDs because of their very small size can be used for variety of lighting application in landscaping. Table 1: Lamps and control gears used in outdoor lighting should be selected based on the minimum efficacy values given in the table below
The exterior lighting power for the applications as mentioned in the table given below as per ECBC 2007 should be calculated and it should be in the limit of recommended values in the table – Table 2: Exterior Lighting Power Densities
c. Integration of daylight – Utilization of daylight can reduce the dependency on artificial lighting during daytime and can help in saving significant amount of energy which would have been otherwise wasted to provide similar visual comforts. d. Lighting controls – Lighting controls in a lighting scheme are directly related to the operations. Controls like dimming, step-down, on-off, occupancy; photocells, timers etc are widely used now a day in lighting schemes.
Controls in Day-lighted Areas a. There should be use of appropriate controls. And it should be well integrated with internal lighting. Each space enclosed by ceiling-height partitions shall have at least one control device to independently control the general lighting within the space. Each control device shall be activated either manually by an occupant or automatically by sensing an occupant. Refer guidance note for the same. Is capable of reducing the light output of the luminaires in the daylighted areas by at least 50%, and b. Controls only the luminaires located entirely within the daylighted area Occupancy sensors These devices – also known as ‗motion detectors‘ – turn lights off and on in response to human presence. Once sensitivity and coverage area is established, sensors are selected from two predominant technology types. Passive infrared sensors These detect the motion or heat between vertical and horizontal detection zones. This technology requires a direct line of sight and is more sensitive to lateral motion, but it requires layer motion as distance from the sensor increases. The coverage pattern and field of view can also be precisely controlled. It typically finds its best application in smaller spaces with a direct line of sight, such as restrooms. Ultrasonic sensors These detect movement by sensing disturbances in highfrequency ultrasonic patterns. Because this technology emits ultrasonic waves that are reflected around the room surfaces, it does not require a direct line of sight. It is more sensitive to motion towards and away from the sensor and its sensitivity decreases relative to its distances from the sensor. It also does not have a definable coverage pattern or field of view. These characteristics make it suitable for use in layer-enclosed areas that may have cabinets, shelving, partitions, or other obstructions. If necessary, these technologies can also be combined into one product to improve detection and reduce the likelihood of triggering a false on or off mode. Photocells
These measure the amount of natural light available and suitable for both indoor and outdoor applications. When available light falls below a specified level, a control unit switches the lights on (or adjusts a driver to provide more light). Photocells can be programmed so that lights do not flip on and off on partially cloudy days. In conclusion one can say that a lighting scheme is optimized when it is effective and at the same time efficient also.
2. Efficiency of lighting scheme 1. Select lamps, luminaires and control gears which are efficient â€“ Efficiency of lamps - Efficiency of lamp is defined by the term efficacy which means the amount of lumen produced by the lamp per unit wattage. Higher the efficacy of the lamp better it is. Also the CRI value of the lamps selected must be in accordance with the application for which it is going to be used. For example in an office space or a display area of a commercial complex one will require lamps with CRI values which will give a very near to the realistic view but on the other hand in case of a street light the CRI will not be the guiding factor in selection of lamp. High efficacy Lamps Lamp efficacy, in an interior lighting scheme, plays a very crucial role. A lighting scheme which utilizes lamps with lower efficacies will result in increased number of lamps and hence increase the LPD (lighting power density) of a space. The increased LPD will not only increase the lighting power consumption but also indirectly increase the heating load on the HVAC equipment and further add to energy consumption The reduction in energy consumption is possible with proper choice of lighting fixtures and the lamp types. Lighting output and wattage should be seen before choosing the lights. Given below are examples of high efficacy lamps currently available in market T5 lamps - These are fluorescent lamps with a diameter of 16 mm, which is 40% less than the diameter of existing slim fluorescent lamps. They are designed for higher efficacy and system miniaturization. The life span of T5 lamps is also very long, around 18 000 hours as compared to 8000 hours of standard fluorescent lamps. Bureau of energy efficiency, India in its appliance energy labelling program has rated various tubular fluorescent lamps, by different manufacturers, on the basis of the energy consumption and light output. Given below is the table listing out the BEE rated TFL lamps Table 3: BEE (bureau of energy efficiency) rated TFL lamps
Compact Fluorescent lamps - CFLs (Compact fluorescent lamps) produce light in the same manner as linear fluorescent lamp. Their tube diameter is usually 5/8 inch (T5) or smaller. CFL power is 555W. Typical CFLs have been presented in figure Light emitting diodes LEDs are small in size but can be grouped together for higher intensity. The efficacy of a typical residential application LED is approximately 20 lumens per watt though 100 lumens per watt have been created in laboratory conditions. LEDs are better at placing lighting in a single direction than incandescent or fluorescent bulbs. LED strip lights can be installed under counters, in hallways, and in staircases; concentrated arrays can be used for room lighting. Waterproof, outdoor fixtures are also available. Some manufacturers consider applications such as gardens, walkways, and decorative fixtures outside garage doors to be the most cost-efficient. LED lights are more rugged and damage-resistant than compact fluorescents and incandescent bulbs. LED lights don't flicker. They are very heat sensitive; excessive heat or inappropriate applications dramatically reduce both light output and lifetime. Uses include:
Task and reading lamps Linear strip lighting (under kitchen cabinets) Recessed lighting/ceiling cans 95
Porch/outdoor/landscaping lighting Art lighting Night lights Stair and walkway lighting Pendants and overhead Retrofit bulbs for lamps
LEDs last considerably longer than incandescent or fluorescent lighting. LEDs don't typically burn out like traditional lighting, but rather gradually decrease in light output. Efficiency of Luminaires – The efficiency of a luminaire is defined by the term ‗luminaire output ratio‘ or ‗the light output ratio of the fixture‘ which is the ratio of the lumen output of a lamp to the lumen output of a luminaire. Higher the ratio means more amount of light produced by the lamp is coming out of the luminaire. Also the light distribution, governed by the mirror optics of a luminaire, plays an important role in selection of luminaires. Efficient luminaire also plays an important role for energy conservation in lighting. The choice of a luminaire should be such that it is efficient not only initially but also throughout its life. Following luminaries are recommended by the NBC 2005 for different locations
For offices semi-direct type of luminaries are recommended so that both the work plane illumination and surround luminance can be effectively enhanced For corridors and staircases direct type of luminaries with wide spread of light distribution are recommended. In residential buildings, bare fluorescent tubes are recommended. Wherever the incandescent lamps are employed, they should be provided with white enamelled conical reflectors at an inclination of about 45°from vertical.
Chapter 7 Conclusions The aim of this study is to evaluate and propose application of passive cooling technique for Indian urban areas in hot humid climate for improving the indoor thermal comfort in naturally ventilated condition towards reducing cooling energy use. To achieve this goal, we implement the study to understand four key aspects, i.e. adaptive thermal comfort in hot-humid climate, existing householdsâ€™ behavior and energy consumption for cooling, passive cooling techniques of vernacular houses and the effects of ventilative cooling in hot humid houses. We evaluate the cooling effects of passive cooling techniques and the resultant indoor thermal comfort using data from various case studies. The findings are compared in order to determine effective passive cooling techniques for the hot humid house; combinations of some techniques are able to meet the indoor thermal comfort requirements. In this paper several passive cooling techniques were reviewed and discussed with reference to their design implications and architectural interventions. The continuing increase of energy consumption of air conditioning suggests a more profound examination of the urban environment and the impact on buildings as well as to an extended application of passive cooling techniques. Appropriate research should aim at better understanding microclimates around buildings, and to understand and describe comfort requirements under transient conditions during the summer period. Also of importance are improving quality aspects, developing advanced passive and hybrid cooling systems, and finally, developing advanced materials for the building envelope.
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Changes in our climate system today in the form of global average surface temperature increase, global average sea level increase and snow c...
Published on Apr 27, 2018
Changes in our climate system today in the form of global average surface temperature increase, global average sea level increase and snow c...