Phase change material coupled building envelope for thermal comfort and energy-saving: Effect of natural night ventilation under hot climate

Incorporating phase change material (PCM) into buildings in hot climates is an excellent strategy for better thermal comfort and energy-saving in future smart cities. Nevertheless, PCM elements suffer from adverse temperature behaviour at night due to the dissipation of stored diurnal heat. Night ventilation has been proposed as a promising solution and clean strategy for decreasing indoor building temperature at night and increasing PCM benefits in the following cycle. In this study, the effect of the natural night ventilation (NNV) period on the thermal performance of a room-integrated PCM is investigated experimentally under hot summer conditions in Iraq. Six NNV periods (with 1 h increment) are studied for six consecutive days in terms of average indoor and operative temperature reduction. Moreover, the work is extended to study the average heat gain difference in each day cycle to show the contribution of PCM to energy-saving. The results showed a slight enhancement in the average indoor air temperature of the PCM room compared with another identical no-PCM room regardless of the NNV period due to high outdoor ambient temperature at night. However, NNV for 4 h can reduce the average indoor air temperature by 28.6% compared with 1 h of NNV, whereas a slight extra reduction was achieved for 5 and 6 h. Besides, NNV slightly affected the operative temperature at night against no impact during the day, which was more influenced by the solar radiation and high diurnal ambient temperature. The results further revealed that a total average heat gain difference of 63.1–87.9 W was achieved, in which the roof contributed by more than 44% in each cycle.