Abstract: A solar collector is constructed on a support structure (such as a roof (14)) that has a plurality of side-by-side channels (16) (for example formed between roof battens (20)), using a length of an elongate web (26) of flexible material that is formed with a plurality of generally parallel passageways for a thermal transfer fluid extending in the longitudinal direction of the web and spaced apart across the width of the web. A first run (26c) of the web is laid along a first of the channels of the support structure so that one face of the web faces out of said first channel. The web is split longitudinally between at least one adjacent pair of the passageways adjacent and beyond the end of said first run and is curved so that the web enters a second of the channels of the support structure. A second run (26d) of the web can then be laid along the second channel so that said one face of the web faces into said second channel.

Abstract: An external building surface formed by at least one of a roof and a wall, the external building surface comprising a plurality of battens spaced apart to define a plurality of transverse courses, a plurality of tiles supported by the battens in the courses defined thereby to provide an outer layer of said external building surface, which tiles are transparent to solar radiation, a plurality of strips arranged one for each course to form an inner layer substantially coextensive with the outer layer, which strips are absorbent to solar radiation, and a duct for a fluid heat transfer medium of a solar heating system extending lengthwise of the strips so that in use the fluid medium is heated when the strips absorb solar radiation incident through the tiles, wherein in each course there is a space wherein air is held over and along the strip in that course.