The role of the external convection coefficient and wind direction sensitivity models in dynamic building simulations

Abstract

This study evaluates the significance of accurately selecting the external convection heat-transfer coefficient (CHTC) in building energy simulations. Two different CHTC correlations were compared: one derived from ISO 6946, which is independent of the wind direction, and another that accounts for the wind direction according to the Emmel model. Dynamic simulations were performed using TRNSYS 18® on a residential building model considering various envelope characteristics, weather conditions, and external convection approaches across three Spanish cities (Almeria, Palma, and Soria). The results indicate that the wind-direction-sensitive CHTC correlation consistently reduces heating demand and increases cooling demand. While the differences in cooling (from 5 to 10% depending on the city) and heating demands (from 1 to 5%) between the models were, generally minor, these effects became more pronounced in climates with extreme conditions, particularly for non-insulated buildings i.e. Almeria and Palma with 5.38% and 24.32% in heating and cooling, respectively. This study highlights the importance of incorporating CHTC and thermal insulation in building design and operation. Proper consideration of these factors can enhance energy efficiency, reduce energy consumption, and maintain indoor comfort, thereby contributing to more sustainable building practices. © 2025 The Author(s). Published by IOP Publishing Ltd.