This paper describes the cooling effect of trees on outdoor and indoor environment in summer, making use of the concept of radiant exergy, which should be applied to the design of buildings and their surrounding open space. The measurement of air temperature, humidity, wind velocity, globe temperature and surface temperature for two days was carried out in order to estimate the radiant exergy of indoor space and outdoor space in the vicinity of buildings and where a lot of trees are planted. We compared the radiant exergy emitted from window surfaces towards the indoor space in north-facing rooms and that in south-facing rooms on the third and sixth floor. Hot indoor radiant environment especially in the perimeter zones, was found due to the warm exergy available from outside and the incident solar radiation reflected by brick pavement outdoors and the roof surface of residential buildings in the vicinity. We have confirmed, through this series of measurement and calculation, that the currents of “warm” and “cool” radiant exergy is useful in quantifying the radiant environmental conditions of indoors and outdoors.
