For years, windows have borne the brunt of criticism about heat- leaking houses. Let’s set the record straight, a window is not the villain some claim it is — if it is the right kind of window.
(1) In cold winters, a single pane of glass is not enough protection. That is why storm windows or double — even triple glazing makes sense. It is the thickness of glass that counts.
(2) Metal allows more heat to escape than glass. Aluminum and steel windows more than ten years old are likely to have no thermal break (a heat-flow barrier of non-metal, usually vinyl). This is applied inside the frames of most new metal windows.
(3) The biggest heat loss from a house occurs not through glass, or even through metal frames, but through holes. Tiny cracks around the window frame, beneath exterior doors, between the foundation and the wall frame, and momentary holes like the occasionally opened front door are enemy.