The Three Pillars of Passive Solar: Gain, Mass, Insulation

Every passive solar building rests on three interdependent principles. All three must be present and properly balanced for the system to work. **Solar Gain** Solar gain is the capture of solar energy through glazing (windows and glazed panels). South-facing glazing (in the northern hemisphere) receives direct solar radiation during the heating season. The amount of solar gain is determined by the size, orientation, and shading of the glazing; the solar heat gain coefficient (SHGC) of the glass; and the number of heating-degree-days at the building’s location. Sizing south glazing correctly is the central design challenge of passive solar: too little, and the building cannot capture enough solar energy to meet its heating needs; too much, and it overheats on sunny days and loses excessive heat at night through the glass. **Thermal Mass** Thermal mass is the material that absorbs and stores solar energy during the day and releases it at…