Those solar space heating systems require at least two penetrations into the building and only perform when air in the solar
collector is warmer than the building room temperature. Most glazed collectors are used in the residential sector.
Unglazed solar collectors are used to pre-heat make-up ventilation air in commercial,institutional and industrial buildings with a high ventilation load. They turn building walls or sections of walls into low cost, high performance, unglazed solar collectors. They employ a painted, perforated metal solar heat absorber that
also serves as the exterior wall surface of the building. Heat conducts from the absorber surface to the thermal boundary layer of the air 1mm thick on the
outside of the absorber and to air that passes behind the absorber. Theboundary layer of air is drawn into a nearby perforation before the heat can
escape by convection to the outside air. The heated air is then drawn from behind the absorber plate into the building’s ventilation system.
