Helping the Sun Heat Your Home in Winter

Every home can benefit from free solar energy in the winter. The first step to taking advantage of this solar heat is to understand where the sun moves around your home. In summer, the sun rises in the east or even a little north of east. It rises high overhead and heats your home’s east walls, its roof, and then its west walls. It sets in the west or northwest. In winter, the sun takes a low arc across the sky, moving from the southeast to the southwest. Most of the sun’s winter heat falls on the south-facing walls of your home.

The key features for harvesting solar heat are your windows. If you replace your windows, select the window glass according to which way the window faces. Most newer windows have insulated glass, which means that they are double-pane windows. This is good in both winter and summer. Many of these double-pane windows also have glass that is coated with a very thin and almost invisible layer of reflective metal. This low-e coating reduces radiant-heat loss from rooms through the window. The new types of spectrally selective glass, like low-e²and Sungate II, are an excellent choice for east and west-facing windows because they also block solar heat in summer. But don’t use a spectrally selective glass on the south-facing side if you want solar heat in winter. Standard low-e glass is a better choice for the south-facing windows, but clear double-pane glass is the best choice.

If you have trees or bushes on the south side of your home, be sure they don’t block your winter sun. Observe the pattern of shadows on your home in both winter and summer. Remember that the shade cast by tall trees helps block that high summer sun, and this helps keep your home cool. But low-hanging bushes or trees may be blocking your winter sun, just when you need it the most. Prune these lower branches to let the sun enter your windows in winter.

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