The number of zero-energy commercial buildings and zero-energy-capable commercial buildings is on the rise across the U.S., according to a report from the New Buildings Institute (NBI) and the Zero Energy Commercial Building Consortium (CBC). Zero-energy buildings (ZEB) in the report are defined as those that produce as much energy as they use through on-site renewable resources. Zero-energy-capable buildings are defined as those that are energy-efficient enough to be zero-energy, but have not taken the step of on-site renewable generation.
The report, “Getting to Zero 2012 Status Update: A First Look at the Costs and Features of Zero Energy Commercial Buildings,” identifies 99 buildings in the U.S. that are either zero energy or zero energy capable, or are ZEBs under construction or recently completed with limited performance data. The buildings are mostly small buildings, but include a range of project types such as K–12 schools, offices, university buildings, recreation centers, and assembly halls.
NBI identified 21 occupied commercial buildings with either measured net-zero energy results (15) or credible modeled expectations (six). The report also found 29 “emerging” ZEB projects under construction and 49 zero-energy-capable buildings.
Key report findings include:
ZEBs have been successfully built in most climate zones of the United States, with buildings constructed in California, Colorado, Florida, Hawaii, Kentucky, Minnesota, Missouri, New Jersey, New York, Ohio, Oregon, Vermont, and Wisconsin. California tops the list with six ZEBs.
To date, the majority of ZEBs are small or very small buildings, but there are an increasing number of examples of larger and more complex buildings. All but two of the ZEBs studied are less than 15,000 square feet and half are less than 5,000 square feet. Many of the earliest examples are academic buildings or environmental centers, in effect, demonstration buildings sometimes with low occupancy levels. More recent buildings include office buildings, K–8 schools, and a credit union—buildings that represent large numbers of “average” or typical buildings.
ZEBs are constructed using readily available technology. An integrated design approach with careful attention to building site and layout, envelope, mechanical systems, and electrical systems is critical to achieve the high levels of energy efficiency. Unique or experimental systems are infrequently used to reach net-zero goals, but the emergence of new technologies will be a factor as this expands to more building types.
All of the ZEBs to date use photovoltaic panels to provide their on-site renewable energy.
As larger office buildings move toward ZEB status, minimizing plug loads and other miscellaneous or unregulated loads is a priority.
Modeling studies indicate costs of 3% to 18% for energy-efficiency features, depending on building type, size, climate, and other variables. Reported incremental costs are only available from a few ZEBs, which makes conclusions or trends difficult to derive. However, the few reported ZEBs appear to show lower overall incremental costs than modeled estimates, possibly due to positive trade-offs with other features in the design and construction process. Those costs range from zero to 10%.
More than 85% of the studied buildings report designs that incorporate daylighting, but there was not enough detail to determine whether effective automated controls were used to maximize energy savings. Two-thirds reported high-efficiency lighting, and more than half reported using a high-performance envelope with increased insulation and glazing. Half of the buildings use natural ventilation.
The report also produces three key recommendations:
Practical guidance is needed to help designers, developers, and owners identify areas of opportunity and available resources.
Data collection efforts should be enhanced.
A better basis for benchmarking performance can come from emerging experience of ZEBs. The benchmarking focus should shift to a forward-looking target of zero energy, rather than a comparison with existing building stock.
“Lofty goals have been set for achieving zero energy buildings by 2030. This study is a first look at whether we could possibly reach those goals. 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,” says NBI executive director Dave Hewitt.
NBI is a nonprofit organization that works with commercial building professionals and the energy industry to promote better building energy performance. CBC members include over 450 commercial building stakeholders committed to charting a path for achieving net-zero energy commercial buildings. The National Association of State Energy Officials (NASEO) serves as the secretariat for the CBC and also co-sponsored the study.