Abstract: A solar panel, comprising a closed body of thermal insulation material with a transparent surface on at least one side thereof, the body having one or more countersunk sections which are lower than the side edges and optional support members, and is surrounded by a transparent sleeve such that one or more air spaces are formed between said sleeve and said lowered sections, the body and the sleeve together constituting an element which is adapted to be installed between structural members in a building or itself constituting an independent wall/roof member.