The relative performance of different approaches to the passive cooling of roofs

Abstract

This communication presents a discussion of the relative performance of five different approaches to the reduction of heat flux through the roof. These are roof shading by plants, use of removable canvas, evaporative cooling, a roof garden and use of earthen pots over the roof. Explicit expressions have been obtained for the time-dependent heat flux entering into the living space through the roof; the living space is assumed to be at constant temperature (corresponding to air conditioning). Results of numerical calculations corresponding to a typical hot day (16 May 1981) at New Delhi have been presented. For optimum thermal load levelling and least average heat flux into the room, a shaded roof (due to a vegetable pergola) with a water film is the best choice.