NOVELTY - The roof structure (10) has a support structure (14) supporting a cladding layer, and a metal backing plates (16) supported on the support structure and in contact with a lower portion of the cladding layer and including pipes (18) for heat exchange of fluid made of polyethylene. The backing plates include body of metal, and the cladding layer is made of metal. A part of area of the cladding layer is in surface contact with the backing plates. The cladding layer is formed of tiles (12), and the backing plates comprise a substrate carrying a metal surface layer. The tiles are made of steel.    USE - Roof structure for a building.    ADVANTAGE - The pipes are made of polyethylene, durable, easy to use, low in cost, light in weight, and have low thermal expansion. The thermal performance of the structure can be enhanced by provision of thermally conductive filler material between the cladding layer and the backing member. The pipes are laid into channels as a single run of flexible pipe, to form required heat exchange circuit, thus minimizing or removing the requirement for access for maintenance after installation. The tiles and the backing plates are made of metal having low thermal mass and the high thermal conductivity such that the tiles heats up quickly in the sunlight, so that the tiles can be quickly placed in a position to allow heat transfer to the exchange fluid. The surface contact between the tiles and the backing plates provides better thermal contact between the components, thus allowing heat to pass from the tiles into the backing plates. The low thermal mass and high thermal conductivity of the backing plates distribute the heat quickly throughout the backing plates, thus making the heat available to the pipes. The structure can collect solar energy in order to improve the energy efficiency of the building on which the roof is constructed.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial sectional view of a part of a roof structure.    Roof structure (10)    Tiles (12)    Support structure (14)    Metal backing plates (16)    Pipes (18)