Abstract: Roof installations consisting of an array of interfitting members e.g. tiles, strips (3), slats or the like which interfit to form a roof covering and a set of heat pipes (7) which run parallel to the plane of the roof (6,1). Heat is abstracted from the heat pipes and used directly or indirectly, e.g. via a heat pump apparatus. Solar energy may thus be captured, as well as ambient energy, e.g. arising from the building below.