In the use of photovoltaic cladding for walls and roofs of buildings, the PV components can experience temperatures high enough to reduce the electrical output well below the rated value. It is shown that reductions in temperature of up to 20 K can be obtained by heat transfer to an air flow induced by buoyancy in a duct behind the PV component, with a significant increase in the electrical output and reduction of heat gain into the building. Practical PV roof installations have been implemented, on the basis of measurements with a fun-scale roof specimen. A numerical model is used, which enables basic design data for PV walls and roofs to be obtained, such as the effects of the depth of the cooling duct on the thermal and electrical performance of the system. The model predictions are confirmed by measurements on a purpose-built test rig and simulations using CFD.