Heat gains to building interiors through roofs : a study based on selected configurations in Sri Lanka

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 modeling 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 order to validate the computational tool, an experimental setup was build and readings were recorded for several days. Same system was simulated using the computational tool and the results were compared. Furthermore, a commercial software and the developed computational tool were used to simulate a selected case and the results were compared with each other.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 modeling 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 order to validate the computational tool, an experimental setup was build and readings were recorded for several days. Same system was simulated using the computational tool and the results were compared. Furthermore, a commercial software and the developed computational tool were used to simulate a selected case and the results were compared with each other.