Retrofitting Your Home for Passive Solar: Adding Thermal Mass

In previous blogs in this series, I’ve been describing one way to solarize your home: by adding passive solar. The strategy I’ve been describing requires installation of windows on the south-facing walls of your home or business to allow the low-angled winter sun to enter, warming your home in the winter.

Sunroom If you end up dramatically increasing the amount of south-facing glass, however, you may need to add thermal mass inside your home or business. Thermal mass is any material that can absorb solar energy during the day and release it at night and on cold days. It serves as a heat sponge that prevents overheating. It helps maintain a more constant internal temperature. Tile, brick, concrete block, adobe blocks and concrete floors are good examples of thermal mass.

Thermal mass is easiest to install in new construction, and much more challenging to install in retrofits. Tiling floor or adding brick facing to nearby walls may help.

For best results, the thermal mass must be in direct contact with the sun. Adding a second layer of drywall to existing walls in direct contact with the incoming solar radiation works well, too. Mass should be a darker color to increase absorption of sunlight.

One note of caution in all of this: for best results, the south-facing windows you install should be shaded by eaves (overhang) to prevent heat gain in the cooling season. You may need to build eaves over these windows if there is no overhang on the south side of the building, or install retractable awnings that can be employed in the summer to prevent overheating.

Adding new windows is relatively inexpensive, though not cheap by any stretch of the imagination. It will help improve the energy performance and comfort of your home, if done correctly, and will increase the amount of daylighting. This, in turn, could reduce electrical costs by reducing the amount of artificial lighting.

Scott's Contracting GREEN BUILDER, St Louis "Renewable Energy" Missouri.http://www.stlouisrenewableenergy.com, contact scotty@stlouisrenewableenergy.com for additional information