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NIST Unveils Zero Net Energy House

Ribbon cutting for NIST Net Zero Energy House.

September 17, 2012 By

In California’s Sierra Nevada, gold-rush era shacks still stand, with shingles made from flattened bean cans, and gaps between boards are filled with newspapers or mud — not what one would call energy-efficient.

Though that was 150 years ago, today’s houses are much warmer, tighter and efficient than they were just few decades ago. But just how far can energy efficiency go? Today, a house that produces as much energy as it consumes — a net zero home — is an attainable goal.

Some approaches to net zero rely on miniscule floor space and wearing heavy body insulation, but the National Institute of Standards and Technology (NIST) has a better idea. Last week, NIST cut the ribbon on a two-story, four-bedroom, three-bath house with 2,700 square feet of living space, plus a 1,500-square-foot basement and a garage equipped to charge electric vehicles — it is a net zero energy test facility with all the modern conveniences that an upscale family might expect.

Nobody lives in this net zero home, but a family of four is simulated by heating, cooling, running showers, cycling washers and dryers, lights going on and off, and running the dishwasher, etc. Even the normal heat and moisture emitted by human bodies is simulated. And all the equipment, appliances, etc., used in the test facility are commercially available.

“You can take a normal home and add solar to it, and it will reduce your energy bill, but it won’t get you to net zero,” said A. Hunter Fanney, chief of NIST’s Building Environment Division. “The most economical steps to doing so are you build it so the shell of the structure – the thermal envelope – is insulated extremely well and is airtight. The second thing you do is pick energy-efficient appliances and heating and cooling equipment. And then the third thing is adding solar.” Fanney said the test facility integrates those things.

In addition to its curb appeal and creature comforts, the test facility — which Fanney said would cost approximately $800,000 to build as a net zero residence — is an engineer’s delight. The roof is covered with solar panels, and three different styles of geothermal systems are buried in the ground. The first geothermal system, Fanney said, “is a long horizontal loop in the backyard [that’s] six feet down in trenches six feet apart, laid out in a serpentine manner — about 1,200 linear feet of tubing.”

At the six-foot depth, Fanney said, the temperature is about 55 degrees Fahrenheit. Three different 400-foot vertical geothermal wells are to the side of the house, and in front is a buried “slinky” coil system of tubing. Geothermal is part of a long-term testing phase that can go on for decades, said Fanney, while the first year will be devoted to achieving net zero.

While the facility is smart-grid compatible, Fanney said that currently, there are no commercially available appliances or heating and cooling systems that are smart-grid ready. “Once the standards are put in place, and NIST has a major role in doing that, the utility can talk to the appliances and heating and cooling equipment,” he said. “Then it’s going to be a substantial change. ... Right now as a residential customer, you pay the same amount for your energy, it doesn’t matter if it’s three o’clock in the afternoon, or three o’clock in the morning.”

Utilities have a lot of excess energy at 3 a.m., but may experience shortages at 3 p.m. on a hot day, Fanney said, adding that the change he sees coming is what he calls “time-of-use pricing.”

“The cost of a unit of energy at 3 a.m. will be substantially less than three in the afternoon,” he said, so dishwashers, clothes dryers and heating hot water can be scheduled for early morning hours to cost less and even out the energy load.

Even without the full smart-grid hookups, smart electric meters currently have four advantages. “Right now, utilities are using smart meters for automatic billing; they don’t have to send a meter reader out,” said Fanney. “And it allows them to connect and disconnect service, and they can do all that remotely.”

And when there’s a power outage, he said, they know immediately where the outage is, in which houses. Additionally, some utilities have a program called green button; once these smart meters are in place, the green button program allows the consumers to use a smartphone or computer to see the energy used by their home on a daily basis.

“You don’t know where it’s used in the home, but at least you can look at your patterns,” Fanney said. “Some studies have shown that if people know how much energy they are using, they will actually reduce their energy use about 6 percent.”

The facility has only been operating for a week, but results will be available soon, as actual operation is compared to computer simulation benchmarks. “The whole mission of NIST is to develop measurement science and metrics to pull new technologies into the market,” said Fanney, adding that energy is an invisible attribute, and the only way the consumer can judge is kind of like the appliance labels — the yellow energy labels that give consumers the anticipated cost of operating those systems over a year. “We hope to develop methods and metrics to better allow the consumer to make wiser energy selections as far as equipment and housing construction in the future.”

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