Direct Gain: Heat Storage

Direct gain is a passive heating technique generally used in cold climates in which sunlight is admitted into the inside space, directly through equator-facing windows, to heat the walls and floors and thereby the air inside. A thermal storage system (masonry floors, walls and/or ceilings) is required to absorb and store the heat during the daytime and release it back at night for space heating. This increases comfort and reduces energy costs. Thermal mass is especially beneficial where there is a big difference between day and night outdoor temperatures.