What Is a Passive Solar Heating System?


A passive solar heating system collects, stores and uses energy from the sun to heat water or an entire building. Passive solar heating is cost-efficient and reduces emissions of greenhouse gases as well as environmental pollution from traditional energy sources. Solar heating system options range from simple architectural design to more complex solar air panels.


  • A variety of methods are used to create a passive solar heating system: indirect, direct or isolated gain. Indirect methods of passive solar design store heat outside the building and use ventilation or fluid movement to conduct it into desired areas. Buildings constructed in accordance with passive solar design principles will directly collect heat and store it in the building itself. Sun rooms can provide isolated areas of passive solar heating.

Architectural Design

  • Buildings designed to optimize the sun's heat are built on an elongated east-west axis as opposed to the more typical box design. Windows are abundant on the south-facing side of the building, and heat-absorbent construction materials such as concrete or stone are used in the appropriate thickness as heat sinks. A sloped roof on the north side of a building reduces heat loss.

Air Systems

  • Passive solar heating with air uses either direct or indirect methods of heat collection to warm air. Direct methods use principles of passive solar design and allow heat to pass directly into a building for storage in construction materials. Fans are used to direct heat to specific areas. Indirect solar heat collection methods store heat between walls or use fans to conduct heat from one place to another. Depending on design and construction, ventilation-based passive solar heating harnesses between 45 and 75 percent of the sun's heat.

Solar Air Panels

  • Solar air panels are an example of a ventilation-based system. They are durable and can meet half of a building's heating needs. They work by collecting heat on plates mounted either on the roof or walls while a sensor monitors temperature of both the building and collector plates. At a predetermined temperature, the sensor triggers a fan to distribute the heat by way of the building's ventilation system. Solar air panel efficiency is negatively impacted by cooler temperatures and cloudy days, making backup heating systems necessary.

Fluid Systems

  • Water or a nontoxic form of antifreeze can collect and transmit solar heat by circulating fluid through a building. Liquid flows from the collection tank to a heat exchanger, displacing cooled fluid back to the collection tank for reheating. Radiant floor heating is one way to efficiently use solar heated fluids, but less-efficient forced air systems are also possible. One important consideration of fluid-based passive solar heating is that fluids may freeze in cold weather, and systems can be prone to leaks.

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