DECC estimates that by the end of 2008, around 10m UK homes had received cavity wall insulation, leaving around 3.5m homes with cavities that could still be filled without significant practical difficulties, according to energy efficiency minister Joan Ruddock.

She told former Conservative shadow environment secretary Peter Ainsworth that: “Approximately 600,000 cavities were treated during 2009, taking the total number of filled cavities to just over 10.5m and leaving an estimated 2.9m homes with cavities considered practical to fill. The Government has committed to filling all cavity walls, where practical, by the end of 2015.”