How Does a Passive Solar Heating System Work? Direct, Indirect & Isolated Gain

These passive solar heating system designs are the simplest forms of design. The passive solar energy is simply allowed to enter the building through properly placed windows. Care is taken to provide good solar energy-absorbing and energy-storing surfaces within the building space. Energy is conserved during the non-sunny hours through good energy-conservation practices.

• Heating:
• Solar energy through large south facing windows heats living area during sunny hours.
• Minimum window area of 20% - 25% of the floor area
• Double or triple glazed windows needed to minimize heat loss
• Correctly fitted insulated curtains, blinds or shutters will be needed
• Paint sun receiving surfaces such as floors with dark colors
• Do not cover tile or concrete (heat absorbing) floors with carpeting
• Consider adding a layer of brick, heavy tiling, or a 2" to 4" concrete overlay to the floor (if the construction of the home could take this weight)
• Consider lining an interior wall with stone or brick
• Create a water wall using a rack of water bottles or an arrangement of barrels ( be sure that the floor is able carry the weight

Cooling:

• Large overhang on south facing windows will shade the interior from the high summer sun, movable shades are ideal, since spring time and fall time heating requirements are very different.
• Plantings of deciduous trees to shade the house during the warm months
• Consider the installation of a trellis over the east and south facing wall which will be planted with deciduous vines
• Do not cover tile or concrete (heat absorbing) floors with carpeting
• Consider adding a layer of brick, heavy tiling, or a 2" to 4" concrete overlay to the floor (if the construction of the home could take this weight)
• Consider lining an interior wall with stone or brick
• Create a water wall using a rack of water bottles or an arrangement of barrels ( be sure that the floor is able carry the weight

Indirect gain passive solar heating systems collect and store solar energy in an area that is not directly in the living area of the building that is being heated. The heat is allowed to enter the room indirectly. Usually the heat is released more slowly than it is received, and this means that heating by passive systems of this sort is more evenly distributed over time, than it otherwise would be.

Examples of indirect gain passive solar heating systems include Trombe walls, water walls, and roof ponds. In these systems the surface that actually transfers the heat of cool is in direct contact with the region that receives the solar heating (or radient cooling).

A passive heating system in which heat is gained in one area to be distributed to another area is an isolated gain passive system. A good example of an isolated gain system is a window box. Window box passive solar heating systems gain the heat in the window box, and allow it to pass into the building adjacent. Solar Greenhouses would be another example of isolated gain passive solar heating systems.

References:

Anderson, Bruce and Malcolm Wells.(1994) Passive Solar Energy Second Edition, The Homeowner's Guide to Natural heating and Cooling. Brick House Publishing Company, Amherst, New Hampshire,

Bossong, Ken and Jan Pilarski. (1982) Passive Solar Retrofit for Homeowners and Apartment Dwellers. Citizens' Energy Project, Wash D.C. report series no.137" Home owner's Guide to Passive Solar: An Overview"