First of all i must say that i have lack of knowledge about physics. I have this silly idea to spray my metal roof in a humid area. No lack of groundwater and im intending to sprinkle my metal roof with groundwater during solar peakhours. The roof is total only 30m2. I understand that thermal conductivity of metal is such that my roof will be cooler underneath if on top flow of cooler water is realised. By cooler i mean a temp difference of at least 10 degree C. So if i put a fan under the roof can the roof function as a sort of radiator and the fan blowing cooler air to the room? Hope my question is understood.