Indirect Gain Solar

Indirect gain solar energy systems use a thermal mass between the sun and the living space. This thermal mass absorbs the sunlight and transfers it to the living space by conduction. Conduction is the way heat moves through materials, traveling from molecule to molecule.


There are two types of Indirect Gain systems:

  • Trombe Walls
  • Roof Pond systems

                   Trombe Walls

A Trombe wall is the most common type of systems. This is a wall that is similar to a giant flat plate collector. The wall is usually 8 to 16 inches thick of dark colored masonry on the sun side of the house. A single or double layer of glass (glazing?) is mounted about 1 inch or less in front of the wall’s surface.

Solar heat is absorbed by the walls dark-colored outside surface and stored in the wall’s mass, where it radiates into the living space. Vents are located at the top and bottom of a Trombe wall to allow heat to convect from between the wall and the glass into the living space. At night the vents are closed and and radiant heat from the wall heats the living space.Roof Pond systems

                 Roof Pond System

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