Heat is collected by tributary canals formed by the space bounded by the rafters of the roof and by a thermally insulated panel at the bottom and by the roof at the top. The tributary cannels collect and concentrate solar energy that has penetrated the roof. The heat is collected by a plurality of tributary canals, in which solar heat is absorbed. The tributary canals are positioned substantially parallel with a building roofs slope such that the higher ends of the tributary canals are in the proximity of the ridge board of the roof at which a mainstream duct collects hot air arriving through the higher ends of the tributary canals. At the end of the mainstream duct an evaporator box for housing an evaporator is placed with a fan that pulls the hot air from the tributary canals and into the mainstream duct and pushes it onto an evaporator.