A passive solar house has a high level of conservation provided by good insulation, windows, and construction. Such a house is also sited so that a lot of windows can be put on the south side. The south side should face within 20 degrees or so of true south, and should be relatively free of obstructions like other buildings and trees.
The photo shows the south elevation of our house. In the northern hemisphere, the sun is low in the sky and the sun shines through the windows, providing heat to the house. In the summertime, the sun is high in the sky and the overhangs prevent the sun from coming in these south windows.
Another passive solar feature we use is called a Trombe Wall. This concrete wall is in the house with fixed windows on the outside; the sun comes in and strikes the wall, heating it up, where it releases heat later in the day. Our wall is covered on the outside with a selective surface coating that absorbs about 90% of the incident solar energy and emits only about 10%. On the inside, the wall is covered with slate and granite.