Saved by zero: What if a house used no energy?


Architect Jeff Christian hopes to one day build a zero-energy home.

As the building industry as we know it seems to be collapsing, and as fuel prices soar, the latest research in energy-efficient building technologies could be poised to revolutionize the way we live. No joke.


Not only have researchers refined various energy saving technologies, but they've begun to integrate them along with various building technologies to make houses energy efficient and affordable.

"It's the integration of all these technologies that's making the difference," says Jeff Christian, nationally-known "energy efficiency guru," architect, and director of the Building Technologies Center at the Tennnesse-based Oak Ridge National Laboratory, pointing out that technologies used creatively with  building design can yield extraordinary results. 

Since 2002, Christian has directed an effort to create "zero-energy" houses, a goal that is close to fruition. Recently, Christian completed five "zero energy" houses in partnership with Habitat for Humanity which were built for about $100,000 each and cost little to power. 

After "tweaking things" over the years, Christian says, the houses have grown increasingly energy efficient, without becoming expensive. Using such things as Structural Insulated Panels (SIPS),  triple-pane glass, geo-thermal heating and cooling systems, even glass that changes from transparent to opaque, Christian says he's built a 1,100 square-foot house that costs about a dollar a day in electricity, and a 2,600 square foot house that cost about a buck-and-a-half a day, compared to a similarly sized conventional house, which costs about $7 a day. 

As he describes the technologies employed, many of them seem to involve more common sense than fancy gadgets. For instance, the geo-thermal heating and cooling systems take advantage of the fact that underground air temperature is warmer than outdoor air in the winter and cooler in the summer. Heat-pumps in the houses draw on this underground air through buried ductwork, a system that normally requires separate and extensive below-ground drilling that can be very expensive. But Christian discovered that a sufficient underground duct system could be installed along with the normal excavation required to build the foundations. And the practical innovation didn't stop there. To take advantage of the heat created by the heat pump units themselves, piping was circulated around the units to supply hot water.

In addition, the main bathroom, the laundry room, and the kitchen are all laid out back-to-back, with a single "utility wall" that contains most of the hot water plumbing coming up between them, which requires the hot water to travel shorter distances through the house. 

Other features include air-tight SIPS that can be easily and inexpensively installed by contractors to create the framed envelope of the house, while proving superior insulation. The houses also include solar panels that heat water and generate electricity. And the standing-seam metal roofs come with "cool colored coatings" that reflect infrared rays and reduce the need for air conditioning.

Since not everyone is in a position to build a nice new green house, one of the houses Christian's center built was a "retro-fit" house– that is, an existing house that was updated with all the energy saving gizmos. "We cut energy use in half in this retro house," says Christian, "a whole house savings of 25 percent."

Overall, Christian says the homes he's built have a HERS index well below the average. The HERS index, or Home Energy Rating system, is the accepted standard by which a home's energy efficiency is measured. In fact, Christian says one of his experimental houses has a HERS index of 31. To put that in perspective, the standard Energy Star rated new home, considered exceptionally energy efficient, has a HERS index of 85. 

Of course, 31 isn't zero. But Christian hopes to get there before too long. More importantly, though, he believes that the home technologies the center has developed are now ready for the real world market. In fact, he says he's working to create a standard building label for homes built in Tennessee based on the HERS index, much like the MPG label for cars, which he hopes might change the way houses are built and marketed.

Here in Charlottesville, builder Mike Kelly knows all about such things. He opts for metal roofs– even though they may cost five times more than an asphalt roof– because the buyer gets lower air-conditioning bills and won't have to think about replacement for 75 years. Such a roof combined with sprayed foam insulation and a savvy sun orientation often adds up to some serious economy.

"You can save $150 a month in heating and cooling bills," says Kelly.

Kelly, however, typically builds high end, i.e. higher-priced, dwellings such as a half-million-dollar contemporary he recently completed near the Rivanna River.

In the affordable, energy efficient housing movement, UVA's architecture department is making its own contributions with its ecoMOD project, directed by assistant professor John Quale. He invited Christian to speak at UVA in October.

"There's nothing like a face-to-face to really impact a design process," says Quale.

So far, ecoMOD has built three ecological, modular, and affordable house prototypes; and plans for a fourth are underway. 

In fact, the ecoMOD project was recently selected as one of 12 finalists for a World Habitat Award, which go to projects "that provide practical and innovative solutions to current housing needs and problems."

"This recognition is meaningful," says Quale, "because the emphasis of the World Habitat Award program is on visionary yet realistic affordable housing strategies that have an emphasis on sustainability."

Indeed, the idea of a 2,000 square foot home for $100,000 that cost a dollar a day to power sounds plenty sustainable. But why stop there? What if homes were affordable and produced energy, like little power plants?

For folks like Christian, that's not so far fetched. In fact, the center he directs has a goal that goes beyond zero: "to create an affordable home by 2020 that could generate more energy than it consumes."


This story is a part of the Green Home Fall 2009 special.