Between The Gaps

There’s a curse of obscure origin that goes: “May you live in interesting times.” Someone must have slipped that message into Sam Rashkin’s fortune cookie, because Mr. Rashkin has been having two very interesting years.

Rashkin oversees the EPA’s Energy Star for Homes program. In 2005, his team set out to revamp the specification that houses must meet to earn the Energy Star label. On top of tougher window and equipment standards, the spec now includes a strict, mandatory “thermal bypass checklist.”

“It’s been a hellacious year,” says Rashkin. “I don’t think I’ve ever traveled as much in my life as in the last 15 months. When you’re a voluntary program and for years you’ve been explaining how you work, and now you go to the industry to say the rules are changing—and you have to justify why they’re changing—you have to accept an amazing challenge.”

PLUGGING THE HOLES So what’s a thermal bypass? Energy Star’s online guide says the term describes “building details where movement of heat around or through insulation frequently occurs due to missing air barriers or gaps between the air barrier and insulation.” Simply insulating isn’t enough, because insulation products, including fiberglass and cellulose, work only by trapping dead air. Exposed to moving air, they may scarcely perform at all.

Bruce Harley of Conservation Services Group in Massachusetts says, “Generally every trade does its job well, but often no one is paying attention to the gaps between them. This is stuff that just disappears once the house is rocked. The energy losses, the moisture problems—all that action happens in places you can’t see. That’s what the checklist is about.”

Take living space built into an attic. Bill Rectanus, who worked for five years as manager of building systems technology for New Town Homes in Denver, says, “Traditionally, people built an attic knee-wall with drywall, insulation, and then attic air space. And you didn’t put anything on the outside of that insulation, because it was in the attic, away from the elements.” But the back of the insulation faces attic air that is frigid in winter and roasting in summer—“and your insulation won’t perform as it should with no protection on the back side.”

“We have hundreds of thermal images showing that these assemblies were not working,” Rashkin says. “R-19 attic knee-wall insulation, according to the infrared cameras, was performing like R-1.”

“It’s a huge comfort issue,” says Rectanus. “In summer, a hot wall can make a room feel like it’s at 80 degrees Fahrenheit even if the thermostat says it’s 72 degrees Fahrenheit.” With air conditioners struggling to handle the unbalanced loads, thermal bypasses can be a formula for customer dissatisfaction.

Missing or exposed insulation behind bath or shower units is another example, says Rectanus. “There are some amazing thermal photo: courtesy dot for dot imaging pictures out there of very, very cold bathtubs. Where in the house do you least want to be cold? The bathtub.”

And big bypasses can torpedo the performance of an otherwise efficient house. Says Harley, “When you mention energy leaks, people think about cracks around windows that you can stick a dollar bill through. But we’re talking about holes in the building enclosure that you can stick your head through, or even climb through.” In training sessions, Harley cites an example he observed in New Jersey: the chimney chase for a zero-clearance fireplace, set behind a wide stone hearth. “The chase was 12 feet wide and 2 feet deep, for a 20-inch metal vent—and it was wide open to a vented attic,” says Harley. “I could have fallen in that hole.” The home’s cutting-edge ground-source heat pump system couldn’t keep people warm: “It ran on electric resistance all winter long.”