ADVERTISEMENT

Net-Zero Energy Buildings Take Hold in U.S.

Buildings that produce as much energy on-site as they consume are becoming more common



Wikimedia Commons/Daderot

A weak economy and rising energy prices have led to a buzz over building efficiency. Light bulb regulations, LEED and Energy Star ratings for homes and appliances, stricter construction codes, and government incentives are all parts of a national effort to cut energy waste in the building sector.

Nearly 40 percent of the nation's energy is consumed by homes and commercial buildings, which means that making them more efficient would not only save money but also drastically reduce carbon emissions. So a handful of builders are taking the idea one step further: Why construct a building that uses less energy when we can make one that uses no energy at all?

That's the philosophy behind "net-zero" buildings, and they have been springing up all over the country in recent years. By the purest definition, a net-zero building produces all the renewable energy it needs on site, drawing no more power from the grid than it gives back.

Considering that a shack in the woods is technically net zero, the concept isn't exactly new. But advances in technology over the past decade have made it easier to design sophisticated buildings that produce 100 percent of their own energy. At least 21 commercial buildings in the United States meet net-zero standards, according to a study released yesterday by the New Buildings Institute and the Zero Energy Commercial Building Consortium.

They run the gamut from offices to libraries to elementary schools. Researchers identified eight more unverified buildings that may also be net zero and an additional 39 that would classify if they installed more on-site renewable energy systems, plus dozens more under construction.

"We are seeing commercial examples of larger and more complicated buildings, which I think is a positive sign," says Stacey Hobart, the communications director at the New Buildings Institute. "Most of these buildings are smaller buildings, and most of them are early market adopters." Universities and local governments have also been responsible for much of the construction, largely because "they have a charge to say, 'This is a net-zero building,'" explains Hobart.

Expanding the possibilities
The first commercial-scale net-zero building was a center for environmental studies, completed at Oberlin College in Ohio in 2000. At that time, the project was largely an experiment in sustainable architecture.

"We intended to create not just a place for classes but rather a building that would help to redefine the relationship between humankind and the environment -- one that would expand our sense of ecological possibilities," said David Orr, the director of Oberlin's Environmental Studies program, at the center's groundbreaking ceremony in 1999. "We now know that such things are possible -- that buildings can be designed to give more than they take."

Commercial net-zero construction has steadily increased since then, with the number of completed buildings more than doubling since 2008, according to the latest study. Thanks to advances in structural insulation, energy-efficient appliances, new government incentives and the falling price of solar, expensive green-building projects -- like net zero -- are now within reach. And they don't always require a commercial-scale budget.

When Frank Walker first stepped inside a net-zero house in Denver two summers ago, he knew he wanted to trying building one himself. As the chief operating officer of a major Colorado homebuilding company, Oakwood Homes, he couldn't believe such a structure was possible.

"It was a 102-degree day in Denver, and the house was 72 degrees with no air conditioning and no cooling systems whatsoever," he remembers. "It's like building a Thermos."

The house was contracted by a local resident who had researched German "passive houses" and wanted to have one of his own. The design was so efficient, says Walker, that "you could heat the house using a hair dryer."

$188,000 homes in Colo.
Inspired by what he saw, Walker decided to replicate the building. With the help of students from a University of Denver work-study program, his company was able to complete two experimental net-zero homes -- the second of which recently sold for under $190,000.

Having perfected its net-zero design, Oakwood plans to start marketing more of the homes in Colorado later this year. Each four-bedroom house will feature rooftop solar panels, a high-efficiency tankless water heater, super-insulated windows and airtight construction.

With a $188,000 price tag -- only $9,000 more than Oakwood's Energy Star version of the same house -- it could soon be the most affordable net-zero home in the country. With about $750 in energy savings predicted annually, homeowners are expected to see a full return on their investment in less than 12 years.

"We've hit a price point that no one else has been able to hit in our marketplace," says Walker, and "we've gotten a lot of great response."

At least a dozen other U.S. commercial homebuilders have begun to offer net-zero residences. The Los Angeles-based company KB Home recently introduced a net-zero option for its houses in parts of Florida, Texas, Colorado and California. Another company, Nexus EnergyHomes, is building 59 duplex units in Frederick, Md., and 14 additional houses near the Chesapeake Bay. The duplexes are about 1,700 square feet -- the same size as Oakwood's homes -- and sell for $275,000 and up.

Each commercial and residential building employs a unique blend of renewable energy and architectural design to reach net zero, but there are some characteristics that nearly every structure shares. Most use solar panels to achieve the bulk of their power and have numerous windows to minimize the need for artificial light. Tight insulation and low-energy appliances are also key elements. Paradoxically, most buildings actually receive electricity bills -- though not very many.

This happens because a net-zero building may need to draw electricity from the grid to power its lights at night, for example, then returns that energy the next day, when its solar panels are most efficient. Likewise, residents may have to pay for heating costs in the winter, but in the summer they would receive a check for their overflow of energy.

Transitioning into a net-zero world without electric bills may sound like a no-brainer, but the technology still faces significant obstacles.

Cost and space remain drawbacks
The success of a building depends largely on the people who use it. If occupants aren't committed to reducing their personal energy use by shutting windows and turning off appliances, a net-zero structure can easily lose its status, becoming just another "efficient" building.

Some areas are also poorly suited for net zero. A building needs enough sunshine to power its solar panels, and that's not always possible in a densely populated city, where tall buildings can cast shadows onto shorter ones. It's also tough to keep structures cool in very hot and humid climates, like in the Southeast, says Hobart. But most experts agree the main barrier is still the price.

"Most building owners aren't going to add 1 percent to their costs. They are just going to build to code," Hobart says. And retrofitting existing buildings to be net zero becomes even costlier.

"When you put all the pieces together, the payback becomes so great that it doesn't make sense," Walker says of the retrofits. Aside from solar panels, thicker windows, and a new heating and cooling system, buildings often need far more insulation than the walls can hold. That requires shrinking rooms or expanding the exterior, which isn't cheap. Walker believes net-zero upgrades are for people who "are less worried about payback and more concerned to do something good for the environment."

Net-zero construction may not be dominating the industry any time soon, but with countless commercial and residential projects in the works, the trend shows no signs of slowing down. Experts say strong government support for building efficiency, coupled with falling costs, means we will likely see more and more net-zero buildings.

"Lofty goals have been set for achieving zero-energy buildings by 2030," says Dave Hewitt, executive director of the New Buildings Institute. "The really good news is extremely energy-efficient buildings are being demonstrated in a multitude of climates and across building types. This is certainly a good sign for the future of zero-energy buildings."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Scientific American Dinosaurs

Get Total Access to our Digital Anthology

1,200 Articles

Order Now - Just $39! >

X

Email this Article

X