Abstract: A solar panel unit for collecting solar heat and imparting it to circulating air has air flow directing means, desirably in the form of a perforated, corrugated baffle plate, sandwiched between a heat collector plate and a backing plate for passing air from one margin of the unit to an opposite margin thereof, with a peripheral wall enclosing the resulting heat collector chamber. Spaced from the collector plate, with a peripheral wall enclosing the resulting dead air space, is a transparent outer panel of glass or plastic for transmitting rays of the sun to the collector plate; and spaced from the backing plate, with peripheral and partition walls dividing the resulting space into air flow passages, is thermal insulation material.