Austin aims for net-zero capable homes by 2015
Builders and homeowners in Austin, Texas, have some pretty aggressive mandates to meet when it comes to energy efficiency for residential homes. The city of Austin, long considered a leader when it comes to energy saving issues, has a directive in place that calls for all new single-family homes to be net-zero energy capable by 2015.
That means builders must incrementally increase energy efficiency to an aggressive 65 percent above the Department of Energy’s IECC 2000 energy building code. That’s a lofty goal, but one that Miki Cook, green building and senior sustainability consultant for Austin Energy, a municipal-owned utility of the City of Austin.
"We are considered an incubator for new green strategies and technologies,” Cook said. “We have a number of builders and architects that have participated in the program since its inception. We teach conservation as a way of avoiding the building of more fossil fuel plants. It’s much less expensive to teach conservation than to build a new power plant.”
The strategy seems to be working. Since Austin Energy founded its own Green Building Program in 1991—the only green-building rating system in the country at the time—the utility has been able to avoid constructing at least two power plants.
Austin Energy served as a consultant for the National Association of Home Builders and the U.S. Green Building Council when those groups developed their green-home rating systems.
Reaching the 2015 directive, which applies to all new homes, re-modeling jobs and retrofits, won't be easy.
“Sixty-five percent is a pretty high goal,” said Khail Zaman, the owner of Z Works Design Build in Austin. Zaman has built only a few Austin Energy-rated homes, and usually builds only one or two a year because of the strict guidelines involved. “If that’s the case, it would definitely make big difference in terms of a home’s energy use. As homes become more efficient, Austin Energy’s service requirements go down and their costs become less.”
The 2015 initiative is administered through the City’s building codes, which apply to all new homes and existing homes as major remodels are undertaken. As it stands now, the Austin City Council’s 2006 energy efficiency requirements pushed 16 percent above the DOE’s IECC code, and the 2009 requirements called for another 18 percent gain in energy efficiency.
“So we’re halfway there,” says Richard Morgan, green building and sustainability manager for Austin Energy. “It gets much tougher from this point, and we don’t see any more significant gains from the envelope. Ultimately, we need to figure out a way to reward design efficiency.”
The Austin City Council has defined a net-zero energy capable home as being energy efficient enough that if the owner put a reasonably sized solar system on the roof, the home would produce as much energy as it uses. The definition takes into account the hot months of July and August, when cooling needs are so high that the home will still pull power off the grid. However, the utility meter would spin backwards during cooler months, banking power credits on the grid.
The Austin City Council doesn’t expect every home to utilize solar power. “There are homes that are just not conducive to solar,” says Morgan. “We obviously don’t want a homeowner in a tree-lined property to cut down trees to accommodate solar panels. But if a home has solar accessibility to provide the power to make that home net-zero, then we encourage that.”
Austin Energy has certified just over 8,000 homes since 1992. Because it certifies new homes for free (there will be a $50 cost per home beginning in October), very few homes in the region have pursued the LEED for Homes certification offered by the U.S. Green Building Council, which can be costly. Cook estimates that Austin Energy certified 25 percent of homes built last year, and expects that number to reach 30 percent for 2010.
The Austin Energy rating consists of a five-star program, with a single star being the lowest rating. The rating system considers energy efficiency, water conservation, material and product selection, health and safety and community issues. Each area can include several design, specification, construction and performance steps, with some relevant to several different building professions and trades.
To assess the quality of workmanship of a home’s thermal-envelope and the HVAC-system installation, various tests must be conducted by a qualified third-party tester, as required by the City of Austin residential building code. These tests scrutinize duct leakage, envelope air leakage, static pressure, supply airflow, return-air sizing and combustion-gas back-drafting. Although there is a modest cost, it can be recouped quickly by the homeowner through reduced utility costs.
A recently rated five-star home, for example, included two 10,000 gallon tanks that held collected rainwater, which is filtered for household use. Rainwater is the only water source for the residence. In addition, the home utilized total-fill insulation, has a standing-seam metal roof, a 16 SEER dual-phase HVAC, no-voc interior paint and salvaged building materials.