Comparison of heat transfer through roof and wall of a house subjected to solar energy in northern malaysia

Abstract

Heat transfer in a house occurs through convection, conduction, and thermal radiation through roof, walls, floor and windows. House materials and direction to where the surfaces of building face, play a role in the total heat transfer for the building. Apart from that the roof slope of house plays a vital role in the intensity of heat from solar radiation that flows through a roof to the attic space bellow it. Reducing the amount of heat that flows through the roof and goes into the attic space can reduce the cooling load and thus reduces the building’s energy cost. This paper discusses the comparison of heat transfer through roof and walls of a house subjected to solar energy, in Kangar – Perlis Region, Northern Malaysia. Solar radiation effect on a house of different roof slope have been investigated. In the same time the heat transfer through the house walls is calculated for the four walls of a house, each facing to the East, West, South and North, respectively. A computer program is developed to compute the effect of solar radiation through different roof slopes and also through the walls. The variation of the ambient temperature, Tair, and solar heat flux incident, qsolar, on each of wall and roof surface throughout the day are chosen for a typical day (day representation in month of March) with 1-h interval. Influence of radiation to the sky is also considered in this calculation. In simulation, we applied the finite difference method to transient problem, where the qsolar, at the walls and roof change with the time as well as the position of the sun along day. From results of investigation, it is recommended that the best roof slope in Kangar has to be taken in the range of 30o- 40o. The comparison of heat transfer per meter square per day between roofs and walls for a house is around 1: 0.867. This ratio is indicated for simple type of house with common materials like brick for wall, asbestos-cement for roof and fiber for ceiling.