The effect of vertical location on thermal performance of multistorey apartments in Riyadh, Saudi Arabia

Abstract

During the recent large-scale development that has taken place throughout the Kingdom of Saudi Arabia in various sectors (e.g., agriculture, industry, transportation, education, and health), many multistory buildings have been constructed with little or no concern for their thermal performance. This paper investigates the effect of exposed roofs on thermal performance during the hot season of the year, by comparing the indoor climate of two apartments, one located on the top floor and the other located on the ground floor of the same building. The internal surface temperatures of the four walls, the surface temperature of the roof, and the indoor air temperature of the selected apartments were recorded automatically, when no air-conditioning was used and the openings were tightly closed to eliminate the effects of natural ventilation and to minimize the effect of infiltration. The surface temperatures of the four walls and the roof were then converted to mean radiant temperature values. The computed mean radiant temperature and indoor air temperature values were then combined into environmental temperature, and these values are presented graphically to quantify the effect of the vertical location on thermal performance. Thermal comfort requirements are also presented for comparison purposes. The results indicated that there is a considerable difference in the thermal performance of the selected apartments due to their vertical location. The indoor air temperature and internal surface temperatures of top floor apartments are relatively higher than the values recorded for apartments located on lower levels, mainly due to the exposure of the roofs of the top-floor apartments to the intense heating effect of the direct solar radiation. Some of the design alternatives for roof construction which have been recently introduced into the Kingdom of Saudi Arabia in an attempt to improve a roof's thermal performance are briefly analysed. The U-values of these alternatives are computed and compared with the U-value defined by the Gulf Cooperation Council (G.C.C.) and the U-value of the roofs of the apartments in this case study.