Thermal mass

Thermal mass, in the most general sense, is any mass that absorbs and holds heat. In the architectural sense, it is any mass that absorbs and stores heat during sunny periods when the heat is not desirable in the living space of a building, and then releases the heat during overcast periods or during the night, when the heat is desirable. The same can be said for not absorbing heat during hot periods of weather. The internal mass remains at a lower temperature than outside keeping the occupants at a more comfortable temperature. Cooling the internal mass can then be achieved by ventilation during cooler periods, typically at night. Thermal mass normally involves some type of solar heating:For example, in passive solar building design, the building might use a sun-facing, uninsulated wall made of adobe, stone, or concrete, called a trombe wall, to directly absorb sunlight. In some buildings, this wall is on the interior, and glass installed in front of the wall increases heat collection by reducing convective heat loss and by focusing the sunlight.In active solar architecture, the building transfers heat between the collectors, the thermal mass, and the living space using water or air, often with a complex pump system.
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