California Leads the Nation in Net-Zero Projects
A tally of net-zero-energy buildings in the U.S. and Canada gives Sacramento the highest city total
A coalition of net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. advocates has completed the first-ever count of net-zero and near net-zero projects in the U.S. and Canada, reporting a total of 6,177 residential units in 3,330 buildings.
The Net-Zero Energy Coalition, a group representing some 180 builders, product manufacturers, designers, and others in the high-performance industry, said that the catalog of North American projects would help the industry track progress over time, create a single point of access for net-zero case studies, and help spread the word about net-zero building.
The projects fell into one of four categories:
- Zero-energy, which produce as much energy as they use on an annual basis.
- “Zero-energy-ready,” in which renewable energy could or does supply at least 90% of the annual energy demand.
- Net producers, which make more energy than they consume.
- Thousand Home Challenge projects, a category that covers deep-energy retrofits of existing homes whether they include renewable energy sources or not.
The largest category by far — more than 84% — is zero-energy-ready. Coalition Executive Director Shilpa Sankaran said that projects could qualify for this group in one of several ways, including participation in a Department of Energy zero-energy program or by tracking energy use over a period of time. Many of these projects are self-reported by builders, designers, or others, she said, with no third-party certification.
The number of residential units actually hitting net-zero performance or making more energy than they consume, was 868, or 15% of the tally.
The coalition found the projects by tapping into data bases of organizations like the Northeast Sustainable Energy Association, Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Institute U.S., the Department of Energy, and the "deep network" of coalition partners and members, Sankaran said.
"It is certainly higher than I expected," she said, "and I've been building zero-energy homes since 2008 when it was very, very unusual. It was much higher than I expected. That said, if you look at the number of homes in the United States and Canada, it's a very small percentage. What that tells me is that the momentum is gaining and certainly there is traction."
The tally was the first part of the project. Phase 2 is the development of a case study directory.
California is the leader
California far outstripped the rest of the country: 1,538 of the total of 3,339 buildings are located there. Twelve of the top 20 cities, listed in order of the number of residential units, are in California, including three of the top five: Sacramento, Davis, and Townsend.
"It has created a market for zero-energy builders," the coalition's report says of the state. "Twenty-four percent of total builders are in California; 23% of all builders have more than one zero-energy project; 11% of builders are performing retrofits as well as new construction, indicating a combination of strategies for zero energy."
Part of that is due to the size of some California projects, including an 800-home development in Sacramento and a huge University of California project in Davis that houses nearly 2,000 residents.
On the East Coast, Massachusetts and Connecticut had the highest number of buildings, with those two states and New York having the most zero-energy builders in the eastern U.S. There are plenty of states without a single qualifying project.
In all, the qualifying projects were about evenly split between multifamily and single-family projects.
The number of net-zero and net producing residential units found in the tally represents about 0.07% of total housing starts last year, but Sankaran seeks promise in steady growth.
"The number of projects that are actually in the design phase, under construction or haven't even been built yet would double the number we have right now," she said. "That's pretty significant."
The coalition sees the net-zero market growing to $1.4 trillion by 2035.
- Net-Zero Energy Coalition
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