Experimental U-values based on measured heat flows through the walls of some houses have been found to be significantly higher than predicted by conventional calculation procedures. The work was carried out in ordinary occupied houses, and included measurements on party, internal and external walls. There are a number of possible reasons for the differences including thermal bridging, high thermal conductivities and excessive air movement in the wall cavities and behind plasterboard dry lining.
Across the world, the dominant form of building construction is heavy, load-bearing masonry or poured concrete, not timber- or steelframe. It is possible to make these buildings very energy-efficient, but they present very different problems from those associated with timber-frame buildings.