Wednesday, February 10, 2010

Windows and Heat in the Winter

Dogs know where to find comfort. Most homes, like this one, bathed by solar radiation in the winter, spurn most of that free heat. You'd think that home designers would have widely exploited the way the sun conveniently bends down low in the winter, sending light and heat streaming deep into a room through any welcoming window. But instead, passive solar homes are a rare exception. Blame the usual suspect: cheap energy.

We try to make our house as welcoming to the sun as its standard design allows, making sure the shades are up during the day and the screens stored in the basement. Most years, I get around to cleaning the windows in the fall. The combination of metal screens and dirt on the windows can reduce how much sunlight gets in, which this window illustrates all too well.

On a sunny afternoon, the greenhouse effect is noticeable, warming the house and giving the furnace a rest.

Glass windows let the energy from the sun in to the house, but prevent the reflected energy from escaping. (The reflected energy is of a different wavelength.) If we could make more use of the greenhouse effect in our homes, we'd leave less of a legacy of greenhouse gases in the atmosphere.