Abstract: A roof or wall face comprises a plurality of battens (216a, 216b) etc space apart to define a plurality of transverse courses each including a space (226). The roof has an outer layer of tiles (218a, 218b, 218c) etc transparent to solar radiation, and an inner layer of metal or other strips (214a, 214b, 214c) etc absorbent to solar radiation. A pipe (228) extends through each space (226) and is thermally connected to each of the absorbent strips. The pipe (228) forms a circulatory duct for a solar heating system. Solar radiation incident on the roof passes through the transparent tiles (218a) etc to be absorbed by the strips (214a) etc, whereby a heat transfer fluid in the pipe (228) is heated for the system. Air held in each space (226) provides an insulative blanket. The strips (214a) etc are formed to provide ventilation and a run-off for moisture.