A trombe wall is a type of solar heating system. The walls are made of a thick heat-absorbing material so they can gather heat during the day and slowly release it into the house throughout the night. A trombe wall is a type of indirect gain solar system, which captures solar heat in an area adjacent to living spaces.
The concept of capturing heat in a wall to keep a dwelling warm at night dates back many years, and trombe walls are only one technique for doing so. Trombe walls were patented in 1881 by Edward Norse although they did not become popular until the 1960s. The trombe wall gets its name from Felix Trombe, who helped make the design popular by building homes with trombe walls in the French Pyrenees.
A thick masonry wall is the main component of this type of solar heating system — common masonry materials used include brick, stone, concrete, and adobe. The walls are usually between 4 and 16 inches (about 10.16 to 40.64 centimeters) thick and face south in order to most effectively capture heat from the sun. Dark glaze is used to coat the surface of the wall so it will absorb the heat. A piece of glass, which may be single or double layered, is mounted close to the surface of the wall. High transmission glass typically works best to conduct heat to the wall.
The trombe wall works by absorbing heat from the sun during the day. Since the wall is very thick, it takes time for the heat to travel through the wall, and heat is stored in the entire thickness of the wall. If a wall is optimally designed, the heat will reach the inside of the wall at dusk and slowly release heat throughout the night. The large surface area of the wall helps to heat the room evenly.
Some trombe wall systems include vents at the top and bottom of the wall. These vents conduct heat into the house during the day. A wall requires 10 to 12 square inches (about 64.5 to 77.4 square centimeters) of vent space per linear foot (about 30.5 linear cm) of wall.
As compared to other forms of passive solar heating, trombe walls have less heat loss during the night. They are also very simple to build and maintain. On the other hand, they collect heat less efficiently than other techniques, and they lose their stored heat and may even leak heat during consecutive cloudy days.