What is Passive Solar Design?

Passive solar design uses a building’s orientation, structure, and materials to capture the sun’s energy and uses this energy for heat, light and ventilation. The building absorbs heat during winter days and contains it to provide warmth at night, while overhangs block heat gain during the summer. Natural convection currents from the sun’s energy move air through the building for improved ventilation and heat distribution. The extra natural sunlight in the home also makes it more bright and pleasant.

To absorb winter sun, the building should be oriented so that the longest wall is facing within 15 degrees of true south. Living spaces should be placed on the south side to take advantage of the heating and lighting, while storage rooms, utility rooms, etc. should be placed on the north side. Evergreen trees should be planted on the north and west sides of the house providing wind break, while trees planted on the south side should be planned carefully as to not block the sun from the house. Deciduous trees will shade the house in the summer and allow sun to enter the house in the fall and winter when the leaves are gone.

The building envelope should be tight with good ventilation. Most of the windows should be located on the south side of the building and windows on the north should be minimal and/or smaller to reduce heat loss. It is wise to invest in high quality windows and insulation/sealing as these components offer quick payback on your investment. Overhangs should be designed to allow the lower angle of the winter sun in and block the higher angle of the summer sun.

Thermal mass is material that soaks up heat during the day and slowly disperses it at night. Concrete, brick, and stone are examples of materials with very good thermal mass properties. The inside walls, floors, and other objects in the home also act as thermal mass. Generally, the more dense the material the better the thermal mass properties. These materials are generally not good insulators but if they are located inside well-insulated outer walls, they will absorb and store heat during the day and disperse it at night.

Passive solar design has economical and aesthetic benefits and it doesn’t have to cost any more than conventional construction. It is worth the investment to work with a qualified design/build team when incorporating passive solar design into your home design. For more information on building your custom home and incorporating energy efficient sustainable features into your plan contact Hammer Builders. For more information on passive solar design, see US Dept. of Energy, Energy Efficiency and Renewable Energy and the National Renewable Energy Laboratory.