A model for analyzing the thermal performance of roof configurations with flat inclined surfaces

Abstract

tThe development of a thermal model, followed by a generalized computational tool that analyses thermalperformance of roofs with four inclined surfaces and a ceiling by considering dynamic environmentaland operating conditions, changes of roof geometry and materials is presented here. Roof elements areanalyzed based on finite-volume method with implicit formulation. View factors of roof enclosures arecalculated numerically. Experimental results, obtained for six actual building roofs under tropical climaticconditions of Sri Lanka, indicated that the thermal model is capable of replicating the actual temperatureprofiles with an average accuracy of 1.1◦C. Ceiling temperature of common roofs were found to be 10◦Cabove the ambient temperature, which could even rise up to15◦C in hot days. The model was successfullyused to compare roofs and quantify the thermal effects of different parameters. For instance, changes ingeometrical parameters led ceiling temperature to change by 5◦C, highlighting the importance of roofgeometry. Out of the widely used three roofing materials in Sri Lanka, clay tile roofing has showed thebest thermal performance. Compared to clay tiles, asbestos and steel roofing can have a maximum ceilingtemperature rise of 4◦C and 6◦C, respectively.