Effects of roof insulation on indoor thermal environment

Abstract

This final report enumerates the research design and presents the results and analysis of the research project carried out under a Senate Research Committee Grant No. 98/01/12.

One of the main contributors to thermal discomfort in tropical buildings is the high incidence of radiant temperature. The primary reason for the increased radiant temperature is the heat gain through the roof composite. If the heat gain through the roof composite could be minimized radiant temperatures inside buildings can be maintained at or around the comfort levels. Together with adequate air movement, such a radiation reduction strategy will enhance the comfort levels of tropical buildings. Insulation plays an important role in controlling heat gain through the roof composite. Since the intensity of solar radiation and solar altitudes are high in the tropics, buildings in this region must concentrate more on minimizing heat gain from roof than any other component of the building envelope.

2. Objectives The present study aimed at ascertaining the degree of thermal insulation of conventional and new roofing materials with / without popular roof insulation systems. The purpose of the exercise was to quantify the reduction in radiant temperature resulting from the use of roof insulation and to rank them according to empirical data. This data will be useful for the estimation of thermal comfort effects of various roof insulation materials which will be studied subsequently.

3. Theory The solar intensity is defined as the rate at which the Sun's energy is received per unit of a surface in the absence of the atmosphere by a perfectly absorbing surface at the mean distance of the earth from the sun and so placed that the radiation falls normally on it. If dQ is the quantity of heat received in time dt by a surface having an area of/1, then the solar intensity /, is given by: