On the road to a low-energy house

During a green building tour, owners and designers say super-efficient homes have many common products and techniques, starting with a very well insulated building "envelope."

Solar panels on Medford, Mass., house
Green-minded renovations to this house in Medford, Mass., include the solar panels seen here. Martin LaMonica/CNET

Building technology is improving every day, but if it's a super energy-efficient dwelling you're after, the tools are already well at hand.

Once a year, the Northeast Sustainable Energy Association organizes a green buildings open house where energy nerds like myself can see the latest in home efficiency.

The homes, which are both new construction and renovations, show that builders, architects, and homeowners have unlocked the code for making buildings dramatically more energy efficient than your typical construction. The question now is whether green building techniques and products will remain on the fringe or become more mainstream.

In a nutshell, the key is to build a house that's appropriately sized and very well insulated, said Doug Storey, the managing partner of Two Storey Building and builder of one of the houses on last week's tour.

If you create a building with a very air-tight and heavily insulated envelope, the heating and cooling needs go down significantly. That not only saves money on monthly bills, it also allows builders to install smaller, less expensive heating and cooling equipment.

"People ask me what the first thing they should do to be more energy efficient [with new construction], and I say it's to build smaller," Storey said, noting that the median house size in the U.S. has been creeping down. "The consumer is not just going for bigger these days."

Could you get to a net zero-energy house? Cutting-edge designer builders have been able to make net zero-energy houses even in chilly New England using a combination of on-site solar energy and air-source heat pumps, which run on electricity. These ductless systems, which do both heating and cooling, work best above about 40 degrees and better suited for smaller homes, Storey said.

The house in Concord, Mass., which Storey is building is too big, at 3,800 square feet, for air-source heat pumps. Instead, it has a similar geothermal ground-source heat pump which, combined with solar photovoltaic panels, will make it consume much less than a similarly sized house.

Deep energy retrofits
What about existing houses? Some of the same techniques are being applied to get 60 percent or more improvement in energy efficiency. There were 32 deep energy retrofit projects out of total of 500 homes on display in last week's tour, underscoring how it's still specialized skill and relatively expensive approach.

Boston resident Edith Buhs and her husband decided on a deep energy retrofit when they needed to reshingle their Jamaica Plain three-family home.

Instead of just shingling over a bare wall, the house received a two-inch-thick layer of foam insulation in addition to the blown-in cellulose in the walls, giving it an R-40 insulation value. The roof and basement also were insulated and made air tight. Snug, insulating fiberglass windows were also installed.

The house's shell has effectively been turned into an insulating thermos, Buhs said. Because it retains temperature so well, she expects they won't turn on the heating until it gets below 50 degrees.

It was an expensive project--$250,000 for the energy retrofit, although the couple received $72,000 in rebates from utility National Grid, which subsidized a number of deep energy retrofit projects last year. That investment pays for itself in different ways, Buhs said.

Financially, she expects this year's utility bills will be about 75 percent less than when they started making renovations. With the clapboards, she'll avoid a few expensive paint jobs. The windows would have had to be replaced at some point, too.

But the energy saving is just one of the benefits from the project, according to Buhs. With the tight insulation, it's more comfortable and noticeably quieter inside. The house it was built with quality craftsmanship that will make maintenance easier over the years, she said.

"For a house we have a long-term commitment to and we live in, I feel it not only makes sense because it's more attractive, quieter, more comfortable, easier to operate and maintain, and it will save us money. But the payback argument comes in not as the trigger, but one of the added benefits," she said. "Nobody asks us what the payback was for our porches."

 

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