Evaluation of passive cooling methods to improve microclimate for natural ventilation of a house during summer

Evaporative cooling is a widely used passive cooling method to mitigate high ambient temperatures in Japan during the hot and humid summer season. An evaporative cooling louver was developed by Hirayama et al. (2014) to create a cool microclimate in an urban residential outdoor space. This study investigated the potential of using passive cooling methods integrated with the louver to create a cool microclimate in a semi-outdoor space for natural ventilation. A field measurement was conducted to evaluate the microclimate in a semi-outdoor space under different amounts of solar radiation, surrounding vegetation, and distances from louver to window to find the best way that accumulates at most the cool air generated by the louver. Best results were found when the semi-outdoor space was exposed to low solar radiation, was fully surrounded by vegetation, and when the louver was closer to the window. Moreover, to use the cool microclimate created at the semi-outdoor space for natural ventilation, different ventilation settings such as window opening area, indoor cross ventilation, and stack ventilation with a sky window were incorporated and measured to find the best conditions to induce the cool air into the indoor space. Best results were found when the window was fully open and the wind speed of the air crossing the window was more than 0.2 m/s, which maintained a cooler vertical air temperature distribution inside the window. •We found an integrated passive cooling method to form a cool microclimate at a semi-outdoor space.•The ambient temperature was reduced by 1.0–4.0 °C when passing through the evaporative cooling louver.•Cool microclimate was formed when the semi-outdoor space was surrounded by vegetation.•Formed cool air was induced into the indoor space when wind speed crossing the window was more than 0.2 m/s.