In 2005, the WWF report “Window of opportunity – The environmental benefits of specifying timber frames” reviewed evidence on the lifecycle and environmental performance of wood versus PVC-U windows, concluding that the overall environmental burden, across several factors, was significantly lower for wood than for PVC-U. More than a decade on, concerns about chemicals in our environment and the rising tide of plastic waste continue. So what does more recent research tell us about the environmental performance of PVCu and the steps the industry has taken towards mitigation of some of the material’s worst impacts? Does the use of wood for windows still rank as the better choice? The Wood Window Alliance has reviewed new evidence to see what’s changed, and whether its members can still confidently present the environmental argument for wood windows.