Construction, maintenance and use of Green Building have significant impact on environment. People’s concern about environment and energy has necessitated the development of the concept of green building. A green building is broadly denied as the building which is sited, designed and operated to reduce negative environmental and has profound positive impact on natural environment, economy, health, productivity and society over its life cycle.
Green building at present constitutes about 5 per cent of the building market. The green building is evaluated by holistic approach where each component is considered in context of the whole building and its social and environmental impacts. The important components of green building are as under:
Materials, Energy, Water, Health.
The materials to be used in the green building should be ecofriendly. These should be obtained from local renewable resources with minimum embodied energy and should be causing minimum waste during its use. These should be recyclable. Such materials will reduce green house gas emissions.
Green buildings use reclaimed materials i.e., use of materials which have been used in previous buildings. Materials such as bricks, doors, windows, frames etc. can be used for another purpose depending on the size and strength, in the new building. This reduces the embodied energy and reduces environmental impacts.
Some toxic materials are used along with the construction materials. Paints for example used as coating material consist of pigments (heavy metals like cadmium, lead and chromium used in pigments), petrochemicals and solvents, benzene, formaldehyde and volatile organic compounds (VOCs) which are used as binder (to hold the paint) and carrier (to disperse the binder). Some preservatives, thickners, thinners, and driers are also used. These toxic chemicals cause indoor pollution and are harmful to human health. These should be replaced by eco-friendly natural products.
The green buildings conform to energy efficient guidelines. Energy Conservation Building Code (ECBC) norms launched on 28 June 2007 apply to all commercial buildings that are constructed in India and have electric connected load of 500 kW or more. ECBC provides design for natural and electrical system for reduction in energy use, 40–60% less energy than baseline building. Solar panels can meet the hot water requirements and efficient lighting. Compact Fluorescent Lamps (CFLs) can reduce the electricity requirements. Natural day light reduces electricity requirement during day time. Heating and cooling costs of such buildings can be reduced by passive solar designs. Use of insulating materials and glass windows play a major role in such designs. Low E glazed windows should be used.
The energy performance rating of windows, doors and skylights is done in terms of potential for gaining and loosing heat and transmitting sunlight into the building.The non-solar heat flow conducted through a window, door or sunlight is measured in terms of u factor which is reciprocal to their energy efficiency (i.e., lower the u-factor more is the energy efficiency). Insulation for heat is an important factor for energy efficient building. Traditional mud houses (consisting of soil mixed with water and straw) are generally found in the villages and this cob technique is also being used in modern construction to have stronger and
thinner walls which provide insulation for heat and noise. During day time the material absorbs heat and the outer exposed side keeps the inside cool while during night time it radiates the absorbed heat to the interior. Stone bricks are also used in buildings which have less embodied energy than bricks from brick kilns although
quarrying of stone has environmental impacts. Natural materials like lime, gypsum, clay etc. can be used for making strong and breathable
walls. A green building can have green roof system. E-rated reflective roof coating will reduce roof heating.
In an attempt to use renewable resources in ecofriendly buildings, the traditional biomass roong (i.e., thatch and wood tiles made from local renewable source) is preferred which forms a biodegradable, appealing and durable roofing. The roof can provide natural substrate and processes for plant growth. A water proof layer (material for water retention) and proper drainage helps plant growth and at the same time protects the roof and building from damage. For green roofs small
plants with brous roots and low water requirements are best suited.
Green roof has the following advantages:
Absorbs atmospheric CO2
Improves energy efficiency.
Causes cooling in summer and provides insulation in winter.
Absorbs noxious pollutants, sound and noise from atmosphere.
Absorbs rainwater which may otherwise flood the sewer lines.
Preserves biodiversity, attracts butterfies, bees and local birds.
Improves aesthetics of the building.
Reducing energy consumption and saving energy will reduce fossil fuel consumption and thereby reduce the threat of global climate change. In green building the use of eco-friendly construction material with low embodied energy helps in reducing carbon emission. This is an important consideration as the building sector
contributes a substantial percentage of green house gases. Carbon emission can further be reduced by reducing energy consumption for heating, cooling and lighting and use of energy efficient gadgets. Reduction in energy consumption in green building will not only reduce global warming and pollution but will also
provide financial savings as the cost of fast depleting fuel will increase in near future.
Water requirement in the green building is minimised. Water is used efficiently by employing water efficient appliances like low flush toilets, waterless urinals etc. The waste water is treated and used for gardening and ushing by the use of double plumbing system. Permeable pavements and rainwater harvesting technology help in recharging groundwater.
Indoor pollution is harmful to the health of residents. People who spend their time indoors with less ventilation get exposed to toxic materials, volatile organic compounds (VOCs) from paints, solvents, plastics and also mites, moulds, spores, microbes, and many other indoor pollutants. They suer from various types of diseases like asthma, headache, palpitation and chronic fatigue, nausea, eye irritation, skin disorders, liver and kidney damage and even cancer.
Green building provides sufficient air circulation and the stale air is replaced by fresh one. The non toxic materials and breathable walls help maintain good indoor air quality. Non-toxic materials like lead free paints i.e., water soluble, natural or organic paints are used. Green buildings with proper ventilation for air circulation are good for health and well being. Natural day light while reduces electricity requirements, also improves productivity e.g., students studying in day light classrooms are known to perform better (20–26% better) than those studying with least day light. Buildings are evaluated on the basis of a number of parameters of environmental importance. Different ratings are given to such green buildings. “Platinum rating” is the highest rating for green buildings. LEED (Leadership in Energy and Environment Design) standards have been developed by USA and many countries have adopted by amending these suitably. A completed building may be rated with different levels as LEED certified, Silver, Gold or Platinum.
Indian Green Building Council (IGBC) and TERI (The Energy and Resource Institute) have developed rating systems for newly constructed buildings. IGBC has set up LEED India NC (LEED India Green Building Rating System for New Commercial Construction and Major Renovations) and TERI has its system called GRIHA (Green Rating for Integrated Habitat Assessment). The classification levels are as under:
Certified 26 to 32
Silver 33 to 38
Gold 39 to 51
Platinum 52 or more
Recently in 2009, Bureau of Energy Efficiency (BEE), taken off from Energy Conservation Building Code (ECBC) of 2007, has started rating office buildings on the basis of their energy consumption in kWh/sq. m./year over a minimum period of one year. The scheme is voluntary and buildings at least one year old are rated on the basis of power consumption, from “one to live” in increasing order of the efficient building. Cities falling in three climatic zones namely, Composite (like Delhi), Hot and Dry (like Jaipur and Ahmedabad) and Hot and Humid (like Mumbai and Chennai) will be assessed on separate assessment parameters.
Source: Online Civil Forum