Design Strategies
Passive solar design integrates building materials and features to minimize the need for mechanical cooling and heating. This design involves proper window orientation and sizing to take advantage of the sun's energy. The type and effectiveness of passive solar design varies with the local climate, passive solar heating techniques generally fall into one of three categories:
- direct gain -- radiation that directly penetrates and is stored in the living space
- indirect gain -- collects, stores and distributes radiation using thermal storage material and uses conduction, radiation or convection to transfer heat throughout the living space
- isolated gain -- collect solar radiation in the area (such as a sun room) that can be selectively closed off or opened to the rest of the house
Materials
To enhance and control the use of the sun for heating, typical elements of passive solar design include:
- Thermal mass: high density materials that store solar heat (sometimes through water storage) during the day that is released at night to heat the home.
- Trombé wall: a masonry wall placed between the aperture (expanse of glass) and the interior heated space. Sunlight is directed towards the Trombé wall through the aperture, stored during the day, and then released at night, sometimes assisted by non-mechanical ventilation.
- Roof overhang: designed to shade the aperture during the summer months; roof overhang dimensions vary according to climate zone, and prevent overheating.
- Bioclimatic chart: when plotted with temperature and humidity data, identifies heating and cooling strategies appropriate for a particular climate zone.
- Solar glazing area: the ratio of solar collection area to floor area required to adequately reduce the heating load of a building, depending on the insulation R-value of the building envelope.
For more information see the National Renewable Energy Laboratory (NREL) publication Passive Solar Design for the Home (Acrobat Reader is required for viewing).
