"Every square metre of window exposed to the summer sun is the equivalent of leaving a one-bar electric heater switched on in your home."
Makes a lot of sense I guess, given that just a few weeks ago I accidentally left a sheet of glass on the front lawn and within an hour or so the sun had well and truly cooked the grass. So whether you're in to the green stuff or not, with the cost of electricity these days it might be worth taking a look at those windows.