Local environmental factors affect the performance of a green building to a great extent. These factors play a significant role in selecting materials and technology for a commercial green building complex. In this paper, an attempt has been made to identify the local environmental factors that affect green building design and to study their effect on selection of green building materials and technology particularly for a typical commercial complex located in Ahmedabad. The major local environmental factors considered in this research work are surrounding buildings, industries, vehicles, population and other factors causing atmospheric pollution. Analysis for recommending materials has been conducted through general study of the properties of the material, their energy saving potential and the conditions in which these materials can be used related to their availability in Ahmedabad, and other site conditions. Energy simulation software "Energy Plus" has also been used to suggest the most suitable material for the commercial green building complex under study. After these analyses, the effect of the regional environmental factors on these suggested materials have been studied and the most appropriate material that can withstand the effect of these factors has been chosen.
IntroductionClimate change has substantial adverse impacts on the community. Most of these changes can be attributed to the effect of global warming. There are many regional or local environmental factors that directly or indirectly contribute to these changes. The effects of global warming have to be combated and one of the solutions is sustainable development or use of energy efficient structures. In this paper, an attempt has been made to identify the local environmental factors that affect green building design and to study their effect on selection of green building materials and technology particularly for a typical commercial complex located in Ahmedabad.
Local Environmental FactorsLocal environmental factors considered for this study are (a) Surrounding buildings (b) Industries (c) Vehicles (d) Population and (e) other Factors causing atmospheric pollution.
(a) Surrounding buildingsThe FSI in the area of the commercial building considered for case study is around 2.25. A similar building with approximately the same area may come up in the vicinity. This may affect the energy consumption pattern of the building under design over the lifespan of the building. Some of the sub-factors affecting this factor are discussed as follows.
- Air movement When moving air strikes an obstacle such as a building, this will slow down the air flow but the air flow will exert a pressure on the obstructing surface. This slowing down process effects a roughly wedge shaped mass of air on the windward side of the building, which in turn diverts the rest of the air flow upwards and sideways. A vortex is formed, referred to as wind shadow. On the windward side such vortexes are at an increased pressure and on the leeward side at a reduced pressure. If the building has an opening facing a high pressure zone and another facing a low pressure zone, air movement will be generated through the building. The wind direction thereby affects the inlet opening size.
- Day light factor Considering a point inside a building, light may reach it from the sun as diffused or skylight, through a window or opening; as externally reflected light by the ground or other buildings; as internally reflected light from walls, ceiling or other internal surfaces and as direct sunlight along a straight path from the sun. Both the ground and the external surfaces of other buildings are usually light coloured, in the strong sunshine, it may create glare. Therefore externally reflected light can only be used providing that great care is taken to avoid glare.
- In the case of tall blocks, the air stream separates on the face of a tall block, part of it moving up and over the roof part of it down, to form a large vortex leading to very high pressure build up. An increased velocity is found at ground level at the sides of the tall block. This could serve a useful purpose, especially in hot climates, although if the tall block is not fully closed but is permeable to wind, these effects may be reduced.
- Internally reflected light would be the most convenient form of daylighting. One suitable arrangement is a high level window which would admit reflected light to the ceiling. If the ceiling is coloured white, this method would ensure adequate and well diffused interior lighting. When a sunlit view through a window is unavoidable, the strong luminance contrast between the view and the window surround can be reduced by painting the adjacent wall a light colour or painting the inside of window frames with white colour. Other openings may be placed in opposite or flanking walls, to throw some light onto the wall surrounding the window.
(b) IndustriesIndustries primarily create air and water pollution due to which air, water or land media becomes unsuitable for specific or established uses.
- Air The most contaminants originating from industrial operations are ammonia, sulphur oxides, nitrogen oxides, hydrogen sulfide, methyl amines, carbon monoxide, particulate matter of carbon origin, particulate matter of dust origin, radioactive gases, methane, chlorine and various organic solvents. Some of the effects of these pollutants are soiling and deterioration of building materials and other surfaces, impairment of visibility, cloud formation, corrosion of metals, deterioration of electrical contacts, deterioration of finishes and coatings and fading of paints and dye.
- Water The categories of contaminants which could have a deleterious effect on water quality include alkaline and acidic materials, colored matter, heated liquids, toxic chemicals, detergents, floating materials, non biodegradable materials, organic matter, suspended solids, mineral salts, algal nutrients, foaming agents, bacteria and viruses. The effects of these contaminants can be degradation of the general area, killing fishes and other aquatic life, increase corrosion of all types of surfaces, lower land use and monetary values of the land surrounding the water, growth of undesirable biological life, often in excessive quantities, interfere with the recreational uses of water, render the water unsuitable for irrigation purposes and make the water unsuitable for industrial use.
(c) VehiclesAutomobile contribute significantly to air pollution. The degree of contribution to air pollution depends on their population, traffic flow and more directly on automobile commuting activities.
The pollutants emitted by automobile are as follows:
The results of these emissions are that the temperature of the area is going to increase.
According to the provisional results of Population Census 2001, the population of Gujarat as on 1st March 2001, was about 5.06 crore, including the estimated population of earthquake affected areas. The decadal growth rate of the decade 1991-2001 has increased in comparison to 1981-1991 from 21.19 percent to 22.48%. As per the 2001 Indian census, the area under Ahmedabad Municipal Corporation has a population of 3,520,085. The population of the Ahmedabad urban agglomeration (which includes the region governed by AUDA) was 4,525,013. The urban agglomeration accounts for 21.7% of Gujarat’s urban population. The increase in population results in the internal heat gain which has tremendous adverse impact on the environment.
(e) Other Factors Causing Atmospheric PollutionThere are several factors causing atmospheric pollution. These contaminants pollute air, water and land. The air pollution problems of cities differ greatly and are influenced by a number of factors, including topography, demography, meteorology, the level and rate of industrialization and socio-economic development. The most common air pollutants in urban environments include sulphur dioxide, nitrogen oxides, carbon monoxide, ozone, suspended particulate matter and lead. The common water pollutants include alkaline and acidic materials, colored matter, heated liquids, toxic chemicals, detergents, floating materials, non biodegradable materials, organic matter, suspended solids, mineral salts, algal nutrients, foaming agents, bacteria and viruses. The common land pollutants include toxic substances, industrial wastes, plastic wastes, harmful chemicals, pesticides, domestic wastes and other non degradable inorganic compounds.
Figure 3: Glare from sunlit surfaces
Figure 4: Reflected light diffused by ceiling
The above factors have a great impact on the local environment and affect natural light and ventilation of the building under design. The temperature of the surrounding area increases by about two degree Celsius. Pollution created by the industrial wastes, vehicles and also the green house gases emitted by the vehicles have a tremendous adverse effect on the local environment. Other factors creating atmospheric pollution and internal heat gain due to population growth also have adverse effect on the environment. All these factors should be considered during design and selection of materials and technology of a green building situated in a particular locality.
Case StudyCase study considered for this research is a green building commercial complex of Ahmedabad. This complex is situated on Sarkhej – Gandhinagar highway. The developer is Ahmedabad based local developer with a proven track record of developing commercial complexes and residential complexes in and around Ahmedabad through the last decade. This is the first green building commercial complex undertaken for development in Ahmedabad region. The project management consultant (PMC) is also an emerging organization from Ahmedabad. The consultant for the services is an organization from Noida, Delhi.
Effect on the Technology Selected for the Green Building Commercial Complex
- Storm Water Management
The storm water management has to be carried out as per the local environmental factors. This comes under the sustainable sites credit according to LEED India CS credit system. The intent is to limit disruption of natural water hydrology by reducing impervious cover, increasing onsite infiltration and managing storm water runoff. The strategy employed is to design the project site to maintain natural storm water flows by promoting infiltration. Thus pervious pavement in form of porous asphalt, porous concrete and open celled or block pavers can be feasible technologies for storm water management.
- Rain Water Harvesting
The rain water harvesting for this project primarily can be 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 Ahmedabad being minimal, rainwater pipes for roof drainage can be installed in the range of 75mm to 100 mm diameter. The rainwater should be collected in pre constructed storage tanks of capacities ranging from 30,000 liters to about 50,000 liters. These tanks can be constructed of reinforced cement concrete, brick masonry, stone masonry, precast concrete blocks or ferrocement.
Figure 5: Rainwater harvesting through sump
- Roof–Heat Island Effect
The heat island effect of roof is considered under the sustainable site credit. The intent is to reduce the heat islands or the thermal gradient differences between developed and undeveloped areas to minimize impact on microclimate, human and wild life habitat. The strategy is to use roofing materials, having Solar Reflectance Index (SRI) greater than 29 for sloped roof and 78 for low sloped roof for a minimum of 75% of the roof surface. Table below indicates the solar reflecting characteristics of some suggested roof materials.
Applying white paint is a viable option but it increases the glare to an uncomfortable level. Asphalt white shingles, red clay tiles and white concrete tiles are applicable at places with sloping roof only. For the commercial complex building under study application of white elastomeric coating or light coloured precast concrete slabs which has a high SRI of 70, appear to be the most suitable, considering the conditions of the building and the availability of the materials.
- Water Efficient Fixtures
This comes under innovative waste water technology under the water efficiency credit. The intent is to reduce the generation of wastewater and potable water demand, while increasing the local aquifer recharge. The strategy is to specify high efficiency fixtures and dry fixtures such as composting toilets and waterless urinals to reduce these volumes. It an also be considered to reuse storm water or grey water for sewage conveyance or on-site wastewater treatment systems (mechanical or natural).
Figure 6: Schematic sketch of composting toilet
For the commercial green building complex under study composting toilets are suggested as a part of the green building initiative. Composting toilets are primarily of two types like a dry toilet fixture or a micro-flush fixture. Urine and faeces move by gravity down a relatively large tube (12-14 inches) that connects the toilet fixture to the composting system directly below. The micro-flush toilet uses a tiny amount of water to carry waste down a 4-inch drain line. Neither fixture has a water trap; instead, a fan pulls air down the fixture, resulting in a completely odourless bathroom. These toilets reduces water usage by about 20% to 50%.
- Energy Efficient Lighting
This comes under the energy & atmosphere credit. The intent is to optimize energy performance of the building and reduce wastage. For the commercial green building complex under study, following energy efficient lighting system are proposed.
- Incandescent to CFL Fluorescent Lamps are about 3 to 5 times as efficient as standard incandescent lamps and can last about 10 to 20 times longer. Since the luminous efficacy of incandescent lamp, 100W is 14 lm / W, where as that of a 40W CFL is 49 lm / W. The saving potential is 80%.
- T12 to T8 / T5 The luminous efficacies of the specified fluorescent lamps are given below, which clearly shows that T-8 and T-5 are more energy efficient. The saving potential of changing from 40W TL to 28 W T-5 is 50%.
- Luminaires An efficient luminaire optimizes the system performance of each of its components. There are a few types of luminaires that offer opportunities for energy conservation in a lighting system design. Many of these provide indirect light to brighten the ceiling or are designed to brighten walls or task surfaces. Most of them are fluorescent and are easily controlled for further energy savings.
- Renewable Energy
This comes under the energy & atmosphere credit. The intent is to eencourage and recognizes increasing levels of self-supply through renewable technologies to reduce environmental impacts associated with fossil fuel energy use. The strategy is to assess the project for renewable energy potential including solar, wind, geothermal, biomass, hydro, and bio-gas strategies. When applying these strategies, advantage should be taken of net metering with the local utility.
The suggested measures for the project under study are as follows:
- Solar photo voltaic cell for external lighting Photovoltaic (PV) cells are semiconductor devices, usually made of silicon, which contain no liquids, corrosive chemicals or moving parts and produce electricity as long as light shines on them. It is recommended for the external lighting in the campus of the commercial complex. Photovoltaic module(s) with a variable total power from 80 Wp to 250 Wp can be used. Advantages of PV cells are that it is a cost-effective and viable option. The basic costs, beginning with a portable PV unit with a 50-watt solar panel, low-power inverter and battery, is about Rs.30000 and can operate three high-efficiency lights, a small TV and a water pump. Disadvantages are that it is not highly efficient as they convert only 12 to 15% of the sun’s light into electricity. PV systems can power any electric device but they are not suitable for water heating or other heat related appliances.
- Solar thermal technology for hot water Solar thermal technologies have a natural advantage in Ahmedabad as well as in India, due to the fact that the average radiation is 4.5–6 kWh /m2/day with an average of 280 clear days in a year. Solar water heating system with tank capacity of 125 lpd has a collector absorber area of 2m2 is designed for 60ºC. For a daily load of 1080 litres at 40ºC, the calculated capacity requirement of SWHS was found to be 340 lpd. The system consists of a collector, a fluid system to move heat from the collector, and a hot water tank for storing heat. There are three main kinds of solar thermal collectors in common use. In order of increasing cost they are (i) Formed plastic collectors (ii) Flat collectors and (iii) Evacuated tube collectors. The collectors can be roof mounted, ground mounted or wall mounted. The working fluid is either pumped (active system) or driven by natural convection (passive system) through it. The method of heat transfer are by open-loop or closed-loop (via heat exchanger) system. The performance of a solar thermal system is best when the solar collectors are installed on a southeast to southwest facing roof receiving direct sunlight for the main part of the day.
- Environmental Quality
This comes under the environmental quality credit. The intent is to reduce the quantity of indoor air contaminants that are odorous or potentially irritating to provide installer and occupant health and comfort. Some of the suggested measures for the project under study are as follows.
- Natural fiber carpet There are two basic types of natural fibers, namely plant and animal. They are stuck directly to a dry, flat surface. Plant fiber includes sisal, coir, jute, seagrass etc. But these fibres are quite expensive and are not resistant to fading and staining.
- Bamboo flooring The advantages of bamboo flooring are that it is extremely hard, stronger than many hardwoods. Some species have been rated higher than maple and almost double that of the red oak. It is also highly moisture resistant. Disadvantages of bamboo flooring are that the technology is pretty inconsistent. Some bamboo forests are being destroyed due to unsustainable management. The embodied energy for transport is high, whenever the bamboo comes from distant forests.
- Reclaimed hard wood flooring Advantages of reclaimed hard wood flooring are that it is easy to clean and maintain irrespective of its color. It has disadvantages such as that it is expensive, because only natural materials can be used instead of synthetic ones. It takes time to set hardwood flooring as it has to be laid in strips or planks. The wood loses its shine over time, giving a dull look to the floor. Sometimes the hardwood flooring becomes slippery and dangerous to walk on in socks.
- Low volatile organic content (VOC) paint Low VOC use water as a carrier instead of petroleum based solvent. Paints and stains must not contain VOC in excess of 200 g /l. Varnishes must not contain VOC in excess of 300 g/l. Benefits of low VOC paints are that it lets out lower levels of ozone pollution and fewer emissions of smog forming chemicals. Low VOC paints are cost competitive and no special equipment is needed.
ConclusionThe various factors affecting the design of the green building in the commercial sector have been studied and each of these parameters was analyzed. The analysis has been based on the consideration of the various regional or local environmental factors that need to be considered during the design. According to the impact of these environmental factors, a detailed model has been proposed by which the process of design of green building has been explained. The analysis has been conducted through energy simulation using the software ‘Energy Plus’ and suitable measures have been recommended. Analysis for recommending materials has also been conducted through general study of the properties of the material, their energy saving potential and the conditions in which these materials can be used related to their availability in Ahmedabad, and other site conditions. After these analyses, the effect of the regional environmental factors on these suggested materials have been studied and the most appropriate material that can withstand the effect of these factors have been chosen. Through this study, a proposed model for a commercial green building complex in Ahmedabad has been developed. This model will act as a guide for future green building commercial projects in Ahmedabad or in similar localities in India.
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