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Home ecology

By JIM MEZZANOTTE

 

If using less energy doesn’t seem to be foremost in the minds of consumers, what about the home construction industry?


What steps are builders taking to improve the energy efficiency of homes? Stan Wrzeski, a professor at the University of Wisconsin-Milwaukee’s School of Architecture and Urban Planning, explains that nowadays it’s best to think in terms of an "ecology of systems; that is, to consider all the various parts of a house that need to work together.

Wrzeski cites the importance of effective ventilation systems. In the last decade, he notes, there’s been a trend towards creating a thoroughly insulated, tightly-constructed "thermal envelope" that limits air infiltration and allows a house to stay warm in the winter and cool in the summer. But as Wrzeski points out, "people, plants, and pets create moisture." Without proper ventilation, a tightly-built house can trap this moisture, which may lead to condensation on windows, internal rot, or high levels of humidity. Also, improper air circulation — for instance, from ventilation fans that create high
levels of suction — can cause drafts, including downdrafts in the chimney. If you move air correctly, Wrzeski stresses, "you minimize the amount of energy you have to use."

To get rid of this moisture and ensure proper air flow, savvy builders install high-quality bathroom fans and range hoods that are suited to a household’s needs, and they also make sure that a house’s thermal envelope is not blocking off the intake or exhaust path of furnaces and water heaters. These devices need what is called "combustion air" to keep their fires going, and as Wrzeski points out, "every cubic foot of air that comes in has to go back out."

To get rid of this moisture and ensure proper air flow, savvy builders install heavy-duty fans in the bathroom and powerful range hoods in the kitchen, and they also make sure that a house’s thermal envelope is not blocking off the intake or exhaust path of furnaces and water heaters. These devices need what is called "combustion air" to keep their fires going, and as Wrzeski points out, "every cubic foot of air that comes in has to go back out."

Nowadays, many houses have what is called "sealed combustion" for their water heaters and furnaces. One pipe brings in air; another takes it out again. Some water heaters now use powered ventilation. In addition, there are recovery systems available that can take excess heat from another part of the house — from an air-conditioning unit, for instance — and put it back in the water heater.

Windows are another important aspect of a house’s total system, because they are typically the weakest link in a house’s thermal envelope. A house’s "r" value refers to the resistance of heat flow, and windows have the lowest "r" value in the envelope. One current trend among builders is the installation of what are called "low-emissivity" or "low-e" windows. These windows are double-glazed; i.e., have two panes of glass with an insulating layer of air or gas in between,with special coatings that reflect radiant heat. In the winter, these coatings throw heat back inside the house, and in the summer, they reflect it outward.

A house, Wrzeski says, should be looked at as several different zones of activity. People can focus improvements in energy efficiency on rooms that they use the most. He adds that some new houses have systems that can shut off different zones.

One important trend in home construction is the establishment of practices and standards for builders to follow so as to make houses more
energy-efficient. The Wisconsin Environmental Initiative offers a program called Green Built Home. This voluntary program is available to builders throughout the state, reviews and certifies new houses based on an extensive checklist, which contains over 200 suggestions on such matters as insulation, sealing, water heating and windows, to name just a few. To receive certification, builders earn points by fulfilling certain basic requirements and then implementing additional suggestions. Consultants from the program make site visits to verify compliance.

Dirk Mason, the director of the Green Built Home program, says good insulation is essential for energy conservation, but notes that the insulation has to be installed correctly to be effective. "How it’s put in really matters," he says. He cites two new insulation trends: permanent concrete forms that insulate a basement, and insulated structural panels that can serve as walls.

A basic requirement for builders participating in Green Built Home is
certification from another Wisconsin program, Energy Star Homes. Administered by the Energy Conservation Corporation, a non-profit
organization that manages all statewide residential energy-efficiency
programs, Energy Star Homes certifies a new house as being energy-efficient after several site inspections and performance tests. Right now, there are 160 builders actively constructing houses in the Energy Star program.

Ed Carroll, program manager for the Wisconsin Energy Conservation Corporation, explains that site inspections help contractors identify ways to improve energy efficiency. For instance, Carroll notes that, when framing a house, contractors often inadvertently create escape routes for air, which site inspectors tried to catch. "Energy Star homes are 23 percent less leaky than the average," he notes. Another overlooked area is a house’s orientation to the sun, so it can take advantage of passive solar energy.

Other forms of solar power — such as solar heating systems, and
photovoltaic, or "P.V." panels, which convert the sun’s radiant energy into electrical current — haven’t yet caught on in the mainstream. "The cost is too high," Carroll notes. However, the efficiency — and aesthetics — of solar technology is improving, and this clean, renewable energy source will
definitely be something to look out for in the future.

Like Wrzeski, Carroll stresses the importance of proper ventilation. "Ventilation doesn’t have to be expensive," he says. "It just has to work well." Whether you’re having a house built or just remodeling, you will ultimately save money by upgrading your bathroom fan and range hoods. Carroll notes that bathroom fans are now available with timers and dehumidistats, which further cut costs. He also suggests upgrading the blower motor in forced-air furnaces and central air-conditioning units. A high quality, variable-speed motor will consume a third the power of an average blower.

One possible future trend is something called "distributed generation." This is essentially local power production, with some kind of small power generator—a micro-turbine, for instance—set up to service a particular neighborhood or city block, perhaps during off-peak periods. But don’t expect this scenario to be arriving at your doorstep any time soon. For now, we’re all in this together.