Numerical assessment of the impact of shading on opaque wall in Malaysian conditions

Solar radiation on building envelope is the main reason for heat gain and thermal discomfort. In the case of Malaysia being a tropical country with high solar radiation,solar heat gain through building envelope is the main reason for cooling requirement. The design criterion for minimizing solar heat gain into a building envelope is known as the Overall Thermal Transfer Value (OTTV), which consists of three main parts:heat conduction through walls, heat conduction through fenestration, and solar radiation through fenestration. Although various strategies such as wall insulation and shading with plants have been developed to control the heat transfer through opaque façades, these strategies have some disadvantages. However, there is no study about the effect of controlling direct solar radiation on opaque facades in Malaysian climate conditions via external fixed shading system. Moreover, since the current OTTV equation and coefficient for Malaysia were initially introduced to apply to buildings with bare envelope, building designers have the problem of computing the OTTV for buildings with external shading. The purpose of this research is to examine impact on heat gain of buildings under Malaysian climate conditions by introducing external fixed shading system on opaque facades. To achieve this aim, a computerized simulation method was used and ECOTECT simulation software was selected as a simulation engine. First, an existing cell in the Faculty of Design and Architecture at Universiti Putra Malaysia camp‟s was selected to validate the model in the simulation package. After preparing the base line model, solar analysis tool was run to assess the solar radiation on building envelope. Thermal analysis was run to consider the indoor thermal comfort condition and cooling requirement. After analyzing the base line model, the effect of external shading on opaque facades was evaluated by introducing the horizontal louver fixed shading devices to the base line model and reassessing the model with louver shading system. Finally, findings for the base line model without shading system and with shading system were compared and the effect of external fixed shading on opaque facades was discussed. Based on the results of solar analysis, variations for solar heat gain through envelope and OTTV were calculated to present the external fixed shading effects on opaque facades. The findings of this research show that the reduction of solar radiation on opaque facades achieved by external shading on opaque surfaces, decreases the solar absorption and as a result of this, there is less solar heat gain by buildings. Equivalent temperature differences (TDeq) for opaque facades are affected by solar radiation and less direct solar radiation on building envelope reduces the TDeq, Thus, heat conduction through opaque facades shows a decrease. It means less solar radiation on building envelope reduces the OTTV for Malaysian climate buildings. Moreover, the results for thermal analysis indicate that by rejecting excess solar radiation from walls,external fixed shading on opaque facades limits the mean radiant temperature (MRT). Therefore, indoor temperature comes down and PMV variation is low. Thus indoor thermal performances improve, and less cooling requirement is needed for providing thermal comfort. The results of this study contribute toward finding optimal ways for architects to design buildings with better understanding of thermal transfer of building envelope as well as energy efficient standards in tropical regions especially in Malaysia for future research