Windows and doors in centrally heated houses in southeast England are opened less often in 2007 than they were in 1984. This is a finding of a recently completed face-to-face survey of home energy use in English households. The survey replicated many of the questions asked in a face-to-face survey in southern England in 1984. When the central heating is on, opening windows increases energy consumption, so the reduction in window-opening over the last twenty years would have saved energy. This paper explores the changes in window-opening behaviours in detail. This research forms part of the UK's 'Carbon Vision' programme on carbon reductions in buildings.