Experimental study on the impact of facade design on indoor thermal environment in tropical residential buildings

This paper presents an experimental study on the indoor air temperature near residential facades in naturally ventilated buildings in tropical climate of Singapore. Four residential sites (Site A-D) with different design features were selected for investigation. Indoor measurements were conducted at locations 30-cm away from the façades. 

Field measurement results showed that windows are of great significance to indoor thermal environment. In vacant units, the peak indoor air temperature reached 44 °C near a large west-facing window at Site A on sunny afternoon, when windows were kept closed and window-to-wall ratio (WWR) was 0.9. Air temperature near the closed window was lowered by 4.1 °C in the afternoon when WWR was reduced from 0.9 to 0.6. Moreover, window openings can effectively lower the indoor air temperature. At Site B, indoor air near a closed window was 7.6 °C hotter than that near an open window with the same orientation and window, and the average temperature difference reached 3.2 °C during daytime (7:00–19:00). In occupied units, air temperature near the north-facing façade was found 4.7 °C higher than that near the east-facing façade in July at Site D, due the sun path in Singapore. The percentages of time with indoor comfortable conditions were evaluated using the cri- terion for Asian residential buildings in summer. It was found that the acceptable time percentages were no less than 80% for indoor locations with daytime or occasional window ventilation. Façade design recommendations were proposed to reduce indoor air temperature and improve indoor thermal comfort in tropical climate.