Method of calculating solar heat transmitted through shaded windows for OTTV in consideration of diffuse radiation diminished

Abstract

The energy used in the buildings in subtropical and tropical countries is mainly for the cooling load requirements for air conditioning in summer, which is evaluated by OTTV value. To ensure a satisfactory OTTV value, the top priority of building envelope designing is reasonable WWR with appropriate sun shading devices to reduce the heat penetrated through window glass into the buildings. Therefore, the accurate calculation of solar radiation through window glass with shading devices is very important. The research aims to calibrate the reduced solar radiation coefficient of the shading device (β) from the original method, thereby completing the OTTV evaluation method with high accuracy. The calculation is based on the sunlight projection to determine the window’s shaded area created by shading devices of any shapes with consideration of diffuse radiation diminished. The results of β calculated showed that in tropical climate, the total solar radiation on the window glass is much lower than the previous method. A computer software built from the proposed theory helps the designer easily choose the optimal sun shading solutions. The research conducts the calculation as an example for horizontal-inclined and the combined of horizontal and left/right vertical shading devices.

Keywords

• envelope thermal transfer value
• sun shading devices
• diffuse radiation diminished
• building energy performance
• tropical region
• overall thermal transfer value