Between Fancy and Functionality: Comparative Thermal Performance Analyses of Selected External Building Shading Elements in Tropical Building Design

Abstract

Tropical region is characterized by high temperature, arising from high solar radiation. Incoming near-infrared energy emanating from excessive direct sunlight leads to increase in the indoor temperature with its attendant indoor thermal discomfort. Thus, there is the need for protection of the interior from this excessive direct heating. One of such protective approaches is the introduction of exterior shading elements to block the incoming solar energy. To achieve this in a typical tropical city of Ogbomoso, Nigeria, several forms of exterior window shading elements are adopted predominantly based on individual preferences, fancies, etc., without scientific consideration for their effectiveness. This study therefore investigated performance effectiveness of each type, with a view to identifying the most effective shading element in the study area. The study adopted the use of multiple/iterative building performance simulation tool, DesignBuilder for evaluating indoor thermal performance of a typical three-bedroom residential building, with regard to four predominantly adopted fixed external shading elements in the study area. Virtual models of five variants of the building were subjected to energy performance simulation analysis, using weather data for Ogbomoso. While the first building tagged Building I was modelled without any shading element, to serve as the control building, the remaining four tagged Building II, Building III, Building IV and Building V were modelled with overhangs, side-fins, hybrids and louvres shading system respectively. Building V recorded highest reduction (56.55%) in the indoor solar gains. This was followed in the order of Building IV (23.90%), Building II (16.00%), and Building III (7.63%). Thus, effectiveness of external louvres system as an external shading device over side-fins and overhangs in the study area could be established. This research is necessary to minimize additional active energy required to reduce the indoor thermal discomfort arising from solar gains (through reduced annual space cooling loads). This will increase building energy efficiency and reduce carbon emissions for overall clean and safe global environment