Abstract
Among characteristics of photocatalysts is hydrophilic property. Taking advantage of this feature, the authors have installed an evaporation cooling system in an experimental building (165 square meters in total floorage) for verification. Under this system, the exterior walls of the building are coated with photocatalysts (titanium oxide) and water is sprinkled over the walls. Tests show that water sprinkling on the outer walls has reduced their surface temperature by five to ten degrees centigrade and the room temperature by one to two degrees.