By Rob Fanjoy
People have used solar energy throughout history — and before. Modern technology, though, lets builders put it to even better use than just sitting in the sun to warm up.
Passive solar design allows a home to be naturally heated and cooled. It requires more time and planning for site selection and choice of building materials during the design process. Features added to the home may include additional glazing, added thermal mass, translucent panels, wider roof overhangs and skylights. Many of these features are on most homes anyway, but they can be selected based on the amount of visible light transmitted and their solar properties such as heat gain.
Examples of passive solar design include:
- Selecting, orienting and sizing windows to maximize winter heat gain and minimize summer heat gain.
- Choosing different glazings for north- and south-facing windows to control solar heat gain.
- Using materials that absorb thermal energy, such as concrete and brick.
- Providing overhangs that shade south-facing windows in the summer but allow light penetration in the winter.
- Locating windows (including skylights) strategically for natural lighting and cooling with prevailing breezes.
- Using translucent structural wall and ceiling panels, which have been used heavily in commercial construction. They make sense for residential because they have higher R-values than traditional windows.
All of these techniques can be used in almost any home, at little or no additional cost.
In addition to passive solar design, builders can also use active solar technologies (also called photovoltaics or PV). Active solar consists of products that convert the sun’s energy into usable heat and electricity. One of the biggest barriers to widespread acceptance of this technology is that many people don't want "ugly" solar collectors on their roofs. Curb appeal trumps energy savings.
But a new category of solar products, called building-integrated photovoltaics (BIPV), may provide an attractive alternative. BIPVs are most common as shingles, but they’re also available in facade materials, awnings and covered walkways. The shingles replace traditional asphalt roofing, standing-seam metal roofing, and slate or concrete tiles. They are very hard to spot from the ground.
These products are so new that there's not yet a representative track record on durability and maintenance. According to the NAHB Research Center, however, existing experience has shown excellent reliability and very little maintenance.
Rob Fanjoy is the former editor of Smart Homeowner magazine. He currently is retrofitting his home in Michigan with green technology and products.
CAPTION: Tierra Concrete Homes (Boone, Colo.) recently won two awards for a 4,025 square-foot home that features a passive solar, patented precast concrete design for optimizing energy efficiency.
| 
