Incorporating a Trombe Wall into a house is one of the most efficient ways to capture the heat of the sun. They work in the mildest to the most severe of climates.
Basically, sunlight strikes the wall through a window, and the Trombe Wall heats up, causing warm air to flow into a room.
Trombe walls are located on the south side of houses. Clear glass is situated three to six inches away from a mass wall (one made out of concrete, rammed earth or dense masonry). See our post on The Solar House: Free Heating for more information.