Four principal materials are used for constructing window frames in the UK: wood, galvanised steel, aluminium and unplasticized polyvinyl chloride (PVC-U). The newest, PVC-U, was little used in the UK before 1970 but since then its use for domestic replacement windows has grown rapidly until it now has a majority share of that market. The use of PVC-U windows in new building is also increasing but has not become dominant.

This Digest draws on BRE research into the durability of PVC-U windows and their performance in service. It compares the key characteristics with those of alternative materials and will make specifiers aware of standards and other requirements that might influence their choice between competing makes of PVC-U windows.

PVC-U doors and conservatories are briefly mentioned.