Abstract: Ventilation air for a building is preheated by providing on a south-facing wall a solar-energy absorbent collector panel with a plurality of air-inlet openings which communicate with air collection channels behind the panel. Outside air passing upwardly along the panel is heated by the heat of the panel which itself is heated by a combination of solar radiation and heat being lost from the interior of the building. The outside air, passing upwardly a short distance along the panel to the closest air inlet opening, is withdrawn therethrough into the air collection channel and expelled into the interior of the building.

Abstract: Ventilation air for a building is preheated by providing on a south-facing wall a solar-energy absorbent collector panel with a plurality of air-inlet openings which communicate with air collection channels behind the panel. Outside air passing upwardly along the panel is heated by the heat of the panel which itself is heated by a combination of solar radiation and heat being lost from the interior of the building. The outside air, passing upwardly a short distance along the panel to the closest air inlet opening, is withdrawn therethrough into the air collection channel and expelled into the interior of the building.