Investigating the thermal performance and Overall Thermal Transfer Value (OTTV) of air-conditioned buildings under the effect of adjacent shading against solar radiation

Abstract

Building energy conservation regulations are formulated for governing the design and operation of energy-efficient buildings. Overall Thermal Transfer Value (OTTV) is one of the performance-based methods for governing the design of energy-efficient building envelope. OTTV is a measure of average heat gain transmitted into a building through the building envelope. In the current OTTV regulation, any shading effect cast by adjacent buildings against solar radiation is excluded from the OTTV calculation. This may result in an inaccurate OTTV calculation. The objective of this study is to develop an appropriate approach for calculating the OTTV of buildings under adjacent shading effect against solar radiation. Firstly, 14 multi-block building developments constructed in Hong Kong were used as a case study. Through building energy simulations and analysis, it reveals that the discrepancy in OTTV calculation between the building cases with and without adjacent shading effect taken into consideration is very substantial; and the percentage difference can be up to 53.48 %. Moreover, 491 existing commercial buildings were identified and selected. Through computer modelling and simulations, a correlation between annual heat gain through building envelope and the corresponding OTTV has been developed. With this correlation, the OTTV of a building under shading effect cast by adjacent buildings can be properly evaluated. Moreover, parametric simulations have been conducted to identify the dominant factors that influence the adjacent shading effect of a building. It is envisaged that the methodology developed in this research work can be applied to other cities with OTTV regulation being implemented, for fulfilling the regulatory requirement on energy-efficient building envelope design.