Direct Gain for Solar at its Simplest

Direct gain is considered the simplest passive solar technique. Passive solar heating itself requires less maintenance than active solar heating, which relies on mechanical devices to distribute heat.

Direct gain solar heating consists of a sun-based, home heating system. As the sun’s rays shine directly into a building, the building’s heat-absorbent thermal mass stores the heat for distribution in the cooler evening hours. Heat distribution occurs through convection.

Direct gain solar designs are most commonly realized through south-facing windows, insulated with a transparent glazing. The glazing helps insulate the indoors, particularly the thermal mass, preventing heat from draining away too rapidly.

A direct gain, passive system can easily be confused with an indirect gain, passive system, which operates using the same design materials. The difference lies in placement. Indirect gain systems place the thermal mass between the sun and the space to be heated. Examples include water walls or Trombe walls. Direct gain systems, however, use the sun’s heat without interference. Therefore, heat collection, storage, and distribution all function within the same space.

The thermal mass, such as a dark colored, concrete floor or heavy internal wall, is located within the room to be heated. As solar radiation passes through the windows, it is trapped in the flooring material or wall mass.

Thermal mass can go beyond masonry to include water filled containers stored within the living space. Water is efficient in this system because it stores more heat than solid materials. The downside to using water is higher maintenance. Unlike masonry, water does not support itself and must be treated yearly against microbial growth.

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Links:

• Direct Solar Gain
• Direct Gain

Direct Gain Thermal Heating