Estimation of heat exchange across multi-facade roof structures for residential buildings

Abstract

Roofs of residential buildings play a crucial role in the context of building heat gains and thermal comfort, since they are exposed to a significant portion of insolation during the day. Therefore, it is important to develop a generalized model to evaluate thermal performance of roof structures under local conditions. This modelling becomes complex due to the dynamic nature of the parameters and various configurations, orientations of the roof surfaces in 3-D space. To address this issue a numerical approach was used to determine view factors of roof surfaces of a generic configuration. Consequently, a thermal model was developed to represent roof structures with four roof surfaces and a ceiling. Model is capable of incorporating insolation on roof surfaces, environmental conditions, roof configuration and materials and obtaining thermal responses of roof surfaces. A computational tool was finally developed based on the model. In this paper, the developed model and the roof thermal responses which were obtained with the aid of computational tool for several roof materials under Sri Lankan environmental conditions are presented and discussed.