Of course, daylight originates at the sun. But more specifically, the daylight that enters a building may shine directly from the sun, bounce off of bodies of water, streets, buildings, or other surfaces, or come from the diffuse, day-lit sky. Placing and sizing windows and figuring control measures, such as roof overhangs, requires a clear understanding of the sun's path. The sun's daily east-to-west arc changes throughout the year. At the summer solstice, June 21, the sun rises and sets farthest to the north, which means that it is higher during the day.

At the winter solstice, December 21, the sun's arc is at its southern-most position, with a much lower mid-day elevation. The sun's angle at any given time of the day depends on your latitude. The further north you live, the lower the winter sun will be in the southern sky. Whether a window faces north, east, south or west makes a big difference in the type of light it receives.

If you want morning sunlight to spray across your breakfast table, your breakfast room window should face east. Light from the south is bright and direct; solar houses are oriented to the south for maximum heat gain. South-facing windows are often located beneath eaves or roof overhangs that block the high, intense summer sun but allow the warmth of the lower winter sun.

Western sun can be intense and glaring. Controlling it is more difficult because, as the sun sets, its low angle dips beneath eaves and overhangs. Shades, blinds or glare-resistant glazing are generally required. It's also helpful if deciduous trees are planted on the west side of a house--their spring-and-summer leaves block unwanted heat, then when the leaves drop in the fall, the trees allow the sun's warmth and light.

North light, never direct from the sun, has cool, bluish hues because it comes from the sky. Because it's constant, north light is favored for artists' studios and the like. Be sure any architect or builder you hire will take all of this into account when planning your house's window placement; ask for references and call previous clients.