A composite insulating panel (17) comprises a profiled external sheet (2) having a plurality of raised crowns (3) of generally trapezoidal form, an inner liner sheet (4) and a body of insulating foam (5) between the sheets (2, 4). The panel (1) has an integral heat collecting means for transfer of heat from one source to another. In one case there are inner conduit (21) through which a heat transfer medium is circulated to extract heat from inside a building and outer conduits (8) for collection of solar heat (9). The panel (17) may be used as part of a heating/cooling/ventilation system.