Seal of Approval

In the eyes of some experts, blocking air movement is the most important energy move builders can make.

“Air movement is a big issue for us,” says C.R. Herro, national vice president of environmental affairs at Scottsdale, Ariz.–based Meritage Homes, which claims to be the only top 10 builder that offers 100 percent Energy Star–qualified homes. Air leakage, especially random air movement through building cavities, can account for 30 percent or more of a home’s heating and cooling costs, according to the DOE.

The first line of defense is to use caulk to seal cracks, gaps, and joints, especially at the connections and elements that penetrate the building envelope. Couple that with an air barrier that has been taped at the seams—which improves the performance by 20 percent—and you have a pretty air-tight, inexpensive building envelope. But the efficiency of this barrier is heavily dependent on how well the shell is sealed and the wrap is installed and taped.

The same performance may be achieved with more reliability by using one of the whole-home air sealing and insulation systems that manufacturers such as Owens Corning or Knauf have introduced recently. Another, even more effective approach—which also happens to be the priciest—is to use spray foam insulation. This approach may be three times more expensive than other methods, but green building consultants say it leaves little to chance. Plus, with an R-value approaching 6 per inch, your walls will be well insulated.

Insulation Nation

Every builder has a preference when it comes to insulation. Most swear by inexpensive batt insulation, but others say the product performs well only when it’s properly installed. "I never recommend batt," Edminster says. "It’s almost impossible to do a good job installing batt insulation. It’s a good idea in theory, but in practice it’s a nightmare to do well and certainly not fast."

At the other extreme, foam insulates very well by completely sealing wall cavities. But it is often highly impractical in production housing because of its cost. For that reason, some builders have resorted to a hybrid system that includes batt insulation, good air sealing, and, as a back up (and to stop thermal bridging), rigid foam board on the home exterior.

Whatever insulation you choose, Edminster says, “it should touch on all six sides (full contact) of the wall cavity.” Also, the DOE says it’s important to exceed local building codes that probably only include minimum requirements that likely will not result in a truly energy-efficient and high-performance home.

Windows on the World

Today nearly every builder selects insulated, low-E, Energy Star windows. But it is important to think about fenestration in a broader context, too. Window placement is just as important as window performance. Unfortunately, that may be dictated by how subdivisions are planned. Even so, exposing windows to direct sunlight is unacceptable, Binkley cautions. Thoughtful placement can do more to cut down on heat gain than a low-E coating. And make sure that windows that do have some exposure to the sun also have appropriate overhangs or protection devices such as trees or exterior shades. Postgreen prefers fiberglass windows for their durability and good looks, and the company avoids certain types of styles. "We use casement windows because they give you a tighter seal [when they are closed], and we avoid using double-hungs or products with a lot of framing," Ludeman explains. "The casement gives you more insulated glass and less framing that can cause thermal bridging." Yes, casement windows do cost more, he says, but to balance it out, the company also uses a combination of operable and fixed glass openings—about 30 percent to 40 percent—that cuts costs significantly.