Solar heat flux reduction through roof using porous insulation layer

India, which is in the mid latitude region, has extremly hot summers on its plains. In Northern and Central region of the country the maximum day temperature often goes beyond 45°C. The temperature inside the buildings, which generally have horizontal RCC roof, is unbearable without air conditioning. The steep rise in the cost of electricity has driven architects and builders to use passive cooling techniques in the construction. In this paper we examine the present methods that use an insulation layer to reduce the heat flux entering the living space bringing out their merits and demerits. Further we present an innovative approach in roof design that incorporates a layer of fly ash pieces which works as a porous insulation layer. The method has been implemented in a residential building in Delhi (28.380N). The experimental results demonstrate that the layer provides excellent insulation and it also shows structural stability.