Commercial and industrial buildings total more than 40% of U.S. energy consumption. The importance of targeting building energy use as a key to decreasing the nation's energy consumption has led to incorporating energy-efficient strategies into their design, construction, and operation.
To that end, seven years ago the federal government instituted the Energy Independence and Security Act of 2007, which requires all federal facilities to become zero net energy (ZNE) buildings by 2030, as well as setting a target for all commercial buildings to become ZNE by 2050.
WHAT IS A ZERO NET BUILDING?
The most common concept states that ZNE buildings produce as much energy on site as they use on an annual basis, says BCC Research analyst Michael Sullivan-Trainor. They are net zero because they do require some energy from the grid, but they are able to balance that with energy they create on site.
“In some cases, this means feeding power back to the grid, whereas in others, they still pull power from it,” explains Sullivan-Trainor. ”In the end, the energy pulled is equal to the energy returned for zero net effect on an annual basis.”
Other definitions go beyond this simple grid relationship and measure the amount of carbon emissions created from supplying energy to the building. The challenge is that most large facilities require the combination of energy from renewable carbon-friendly sources and grid-based energy that is produced via traditional carbon-emission processes.
Sullivan-Trainor says this second constraint emphasizes the use of renewable energy sources to be truly net zero, (also known by the acronym NZE) both in energy consumption and carbon emissions, for the most effective positive environmental impact. Thus, ZNE with respect to the grid and zero energy with respect to the environment are important distinctions when considering ZNE building requirements and solutions from both regulatory and design standpoints.
ZERO NET ENERGY VERIFICATION
As ZNE initiatives increase, determining whether a building has achieved ZNE status is spawning a growing verification requirement. ZNE verified buildings or districts have been documented to have met all net energy use through onsite renewables over the course of a year. The energy use of all fuels (e.g., electric, natural gas, steam) is counted and offset by production from onsite renewables.
Last August, the 2nd Annual Net Zero Energy Building Conference (NZEB-C2) showcased the emerging energy efficiency building technologies, as well as case studies of net zero building performance and how design and performance were achieved.
ZNE status is achieved through one of three verification methods, explains Sullivan-Trainor. One verification method requires associations or consultants to review monthly measured energy consumption data for all fuels and the renewable energy production data as provided by the ownership or design team. A second approach is representation by a third-party entity of the measured data via an evaluation report, published article, presentation, or citation in an award or other public forum.
The third verification method, as in the case studies cited at NZEB-C2, is administered through the International Living Future Institute (ILFI) as part of the Living Building Challenge or Net Zero Energy Building Certification. The ILFI definition requires 100% of the project’s site energy to be carbon neutral (i.e., zero direct use of gas and other fossil-based fuels at the site) and supplied by renewable energy on a net annual basis.
The ILFI is an environmental non-governmental organization committed to catalyzing the transformation toward communities that are socially just, culturally rich and ecologically restorative. The institute’s Net Zero Energy Building Certification (NZEB) is the only program in the world that verifies net zero energy building performance.
ZNE verification does not restrict gas or other fuels, but it requires that all fuels be accounted for in the whole building energy total EUI, Sullivan-Trainor says. Documented onsite renewable production must then equal or exceed the energy use of all fuels over the course of a year.
NZEB-C2 RECOGNIZES NZE AWARDEES
The NZEB-C2 recognized the Bullitt Center, which was awarded ILFI’s Full Living Building Challenge (LBC) certification by ILFI.
The ILFI Full LBC certification, the most rigorous of three sustainable rating programs offered by the ILFI, designates that a building has a “positive regenerative” or “restorative” impact on the environment, writes Patricia Kirk.
She reports that Brendan Cook, net-zero energy manager at the ILFI, explains that “a building must demonstrate at least 105 percent net-positive energy and water performance for 12 continuous months before it is awarded full certification.” According to Kirk, only eight U.S. buildings have attained this level of sustainability, the largest of which is the Seattle’s Bullitt Center.
BULLITT CENTER EARNS LIVING BUILDING CERTIFICATION
To earn the certification, the six-story, 52,000 sq. ft. office center demonstrated that it produces more electricity from solar panels on its roof than occupants use in a year. In addition, toxic chemicals were screened from all building materials and all wood was Forest Stewardship Council certified. Its occupants’ human waste is composted and rainwater is captured for all uses, including drinking, states the center’s media release.
“We made a huge, bold bet that human creativity could overcome dozens of unprecedented challenges,” said Bullitt Center CEO Denis Hayes. “If Living Buildings can be built and operated in Seattle, the cloudiest major city in the contiguous 48 states, they can and should be built everywhere.”
In 2014, the Bullitt Center produced 60 percent more energy from solar panels on its roof than it used, largely due to efficiencies that exceeded expectations, making it the most energy efficient office building in the United States.
SANTA MONICA’S CITY SERVICES BUILDING TARGETING FULL LBC CERTIFICATION
Patricia Kirk writes that “designers of Santa Monica’s proposed $57 million, 50,000-square-foot City Services Building plan to apply strategies similar to those used at the Bullitt Center to achieve full LBC certification.”
The building’s sunny southern California location and exposure to consistent ocean breezes that provide natural ventilation could help it achieve net-zero energy. Kirk notes that “strategies to reduce the building’s energy and water demand include:
- a high-performance building envelope;
- natural ventilation, with a radiant slab and panels providing heating and cooling;
- thermostats set at 78 degrees Fahrenheit (26 C);
- electrochromatic glazing and shadow boxes on the glass facade to reduce solar heat gain and increase natural daylighting;
- LED lighting;
- sensors that adjust lighting and room temperature as needed; and
- water-saving fixtures, including composting toilets.”
The global market for zero net energy (ZNE) for commercial buildings will total $239.7 million by 2018, reports Sullivan-Trainor. The compound annual growth rate (CAGR) of ZNE investments will be 50.6% between 2013 and 2018. This trajectory is expected to continue, and market volume will increase as residential buildings are added to the spending, he adds.