Affordable Zero Energy Homes

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Zero Energy Home Enters Affordable Range
Tracy Staedter, Discovery News


May 31, 2006 — A for-profit home builder has constructed a house priced under $200,000 that, in an average year, costs nothing to power or heat.

The so-called zero-energy home, built by Norman, Oklahoma-based Ideal Homes, is priced affordably even though it incorporates some of the latest technology and energy-efficient construction available today.

"I think Americans have this concept in their head that a zero-energy house costs a million dollars," said Vernon McKown, co-founder of Ideal Homes, who partnered with the U.S. Department of Energy's Building America program for the project.

In fact, a zero energy house built two years ago in Frisco, Texas by Aderson Sargent Custom Builder, spanned about 3,000 square feet and was priced at around $1 million.

But for Ideal Homes' 1,650 square-foot house, McKown worked with the Boston-based Building Science Consortium, an architectural consulting firm, to use computer simulations developed by the National Renewable Energy Laboratory (NREL).

The simulations showed how making a few construction modifications as well as adding some high-end technology could achieve the energy-efficient abode.

For starters, the builder added long-lasting compact fluorescent lights, which use far less energy than incandescent bulbs. And instead of laying down pink fiberglass insulation, they blew in cellulose, which is better at reducing air flow within walls and ceilings.

Other modifications — including installing vinyl-framed, low-emittance windows, sealing duct work and installing heat-reflecting solar board under the rooftop shingles — helped reduce the home's energy requirements. Then getting it down to zero required investing in a few high-end components.

Instead of using a conventional air conditioner and furnace, the home was outfitted with a ground-source heat pump. This equipment circulates a fluid through coils of pipes buried 200 feet in the ground, where temperatures remain constant at about 60 degrees Fahrenheit.

The system uses the piped fluid in combination with a heat exchanger or a heater to cool and heat the house.

Because the starting temperature is always around 60 degrees, the rest of the system doesn't have to work hard to reach the desired comfort zone, which may be somewhere between 68 and 74 degrees.

Ideal Homes also installed a tankless water heater, which works to instantly heat temperate water on an as-needed basis.

Although all of these components work together to reduce the home's overall energy consumption, a zero-energy home must generate its own power. To this end, Ideal Homes installed rooftop solar panels, which produce approximately 6,600 kilowatt hours of electricity per year.

During months when the house needs more energy, it draws it from the local power grid. But during months when it is producing more electricity than it needs, it transfers the energy back into the grid for a credit.

At the end of the year, the home's energy bills averages zero.

So far the home, built in September 2005, is living up to its claim.

"It's saving about 85 percent [of the] energy from the builder's normal product, which is already better than code," said Ron Judkoff, director of the Buildings and Thermal Systems Center at the NREL.

Ideal Homes is currently renting out their zero-energy home in order to retain rights to study its performance over time. Knowledge they gain from this house will go into incorporating energy-efficient technology into their mainstream production.