The traditional buildings or houses in India were great architectural example as far as energy efficiency is concerned, since various native features used to be incorporated. The thick walls used to act as insulators. Buildings in hot and dry geographical regions had corridors directing wind to cool naturally. For wet regions, natural light and breeze were used (Business Standard, March 2010). Hawa Mahal or palace of Winds or Palace of Breeze in Jaipur, India is one the magnificent structures with articulated windows that provide cool breeze in a desert area and Golkanda where ventilation is designed to let in fresh cool breeze in spite of summer.
The recent concrete construction lacks environment friendly design. With its expansive growth, building and construction sector has a significant impact on environment and available resources.
“More than 62% decline in the availability of natural resources has been observed in last 4 decades. The Real Estate sector has been one of the major energy consumer and emitter of green house gases (GHGs). The sector has more than 50% share of resources, also accounts for more than one third waste generation worldwide.” observed by the Millennium Ecosystem Assessment Study 2005. The increase in urban pockets development and population makes it very challenging. The particulate matters and the other hazardous substances used and emitted during construction activities contribute the environment degradation. The non recyclable materials such as mercury, fluorescent bulbs, batteries, hazardous waste and lead based paints etc. poses serious threats on environment as well as health.
Urban Heat Island Impact (UHI)
The unplanned construction has let to one of the most significant impact called Urban Heat Island (UHI), which leads to hotter cities due to the following reasons
• Spacing between buildings and building dimensions has been very low
• Relatively dense building material used in construction are slow to warm and cool, this store a lot of energy
• Replacement of natural surfaces by impervious or water proof surfaces, leading to a drier urban area, where less water is available for evaporation, which offsets heating of the air,
• Lower surface reflectivity to solar radiation — dark surfaces such as asphalt roads absorb more sunlight and become much warmer than light-colored surfaces,
• Waste heat generated by energy usage is a secondary contributor
The UHI is mostly noticeable during the summer and winter. Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons, and decreases the occurrence of weak tornadoes. The UHI decreases air quality by increasing the production of pollutants such as ozone and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems. Heat islands results in human discomfort, health risks, increase in energy use, air pollution, release of green house gases, and higher costs due to greater water and energy use. With the increasing urbanization all over the world, especially in tropical countries, it has potential to contribute to global warming directly or indirectly.
Around 61% of population is expected to live in urban area by 2030. This will increase the impact of urban heat islands on human health as well as on global warming directly and indirectly. The observations on the climate change over large cities over the past century show similarities with projected future climate changes. Therefore cities may serve as a model for assessing the impacts of, and adaptation strategies to, climate change on both local and global scales.