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Note 47. Passive Solar Heating Design

The Energy Efficiency Manual includes a group of energy conservation measures that exploit passive solar heating. This Note presents the general principles of passive solar heating.

Passive solar heating is the direct use of sunlight for space heating. Sunlight is brought into the building through skylights, clerestories, windows, or other glazing. The amount of sunlight entering the space must be controlled. The solar energy must be stored for dark periods, usually with heat storage in thermal mass. Stored heat must be released in a controlled manner. Although the name is “passive”, a successful system may require a variety of active components.

Passive solar is much more complex than generally realized. The main challenge is not collecting sufficient heat, but avoiding adverse side effects. Passive solar requires large glazing area, and this causes problems of excessive air conditioning cost, excessive heat loss during cold weather, condensation, and discomfort.

This Note explains which applications and locations are favorable for passive solar, and helps you select the components your system will need. Design issues include the energy saving potential for heating and lighting, which relate to the glazing area and location, absorption of sunlight into thermal mass, distribution of heat within the building, methods of limiting heat loss, selection of the storage medium, control of heat storage input and output, coordination with daylighting and electric lighting, coordination with the building’s heating and cooling equipment, longevity of the materials, installation methods, preventing water leakage from rain, wind and snow loads, maintenance, exterior appearance, interior esthetics, and cost.

The Note also includes a detailed comparison between active solar heating systems and passive solar heating.