Smart Roof for Green Building in Small City

Abstract

A cool roof is defined as the one that reflects the sun’s heat and emits absorbed radiation back into the atmosphere. The roof thus, remains cooler and reduces the amount of heat in the building. It is well known that light colored reflective surfaces heat up less in the sun. Cool roof may be white, but it need not necessarily be white as there are cool colours available which use dark coloured pigments and still are highly reflective. Cool roof can be compared with white shirt; normally one prefers to wear the same reason during summer. Cool roofs reflect more sun lights and absorb less heat than traditional dark-coloured roofs but most of the roofs in the world are dark-coloured. In the heat of the full sun, the surface of the black roof can increase the temperature as much as 50 degree centigrade. Cool roof provides through solar reflectance surfaces which are comparatively cool and thus provides comfortable conditions inside the houses. The advantage of cool roof, properties and cool roof based on the solar reflectance and thermal eminence and describes essential materials for a green roof construction. The paper discusses the importance of green roof in Bangalore city to control the temperature increase. It suggest roof garden as one of the solution to deal with the heat island phenomenon to fight the urban heat island effect.The most important feature of an ideal cool roof is that its surface strongly reflects sunlight. The surface of an ideal cool roof should also efficiently cool itself by emitting thermal radiation. Thus, a cool roof should have both high “solar reflectance” (ability to reflect sunlight, measured on a scale of 0 to 1) and high “thermal emittance” (ability to emit thermal radiation, also measured on a scale of 0 to 1). The solar reflectance and thermal emittance of a surface are called its “radiative” properties because they describe its abilities to reflect solar radiation and emit thermal radiation. For cool roof design parameters like solar reflectance index (SRI) and thermal emittance are defined and the values are obtained for cement, paint and other materials. Based on the discussion it is recommended to have high values of SRI to construct a cool roof in Bangalore.