Abstract: There is disclosed a building structure partially covered with siding panels, the outer surface of which are transparent to solar energy, the panels being slightly spaced from an insulating wall of the building to allow a fluid flow, preferably air, therebetween with effective heat exchange from a solar radiation absorbing surface with the fluid being selectively utilizable for space heating purposes or other purposes. The air can be moved by fans or convection or both. A preferred embodiment employs small horizontal lenticular lenses in the transparent material on the surface of the siding together with a mask, which may be three dimensional, on the back of the siding with the result that when the siding is viewed from the horizontal it displays a decorative color while it is highly reflective for solar rays at high angles of elevation and is transparent for solar rays at low angles of elevation, as during winter months.