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Making Zero Net Energy Buildings a Reality for California and Beyond


In the same way California implemented the nation’s most rigorous vehicle emissions standards, the Golden State has in place what arguably is the most stringent energy efficiency requirements for buildings. The state’s Title 24 Building Energy Efficiency Standards require all new commercial construction to be zero net energy (ZNE) by 2030. In other words, they must produce on site from renewable sources all of their own power.

As with other commercial and institutional facilities, Title 24 has major implications for the design of building envelopes in California schools and hospitals. Even if you focus on projects outside California, it is beneficial to understand what ultra-efficient building envelope systems are available, as regulations developed in California often make their way to other states and cities.

The Building Envelope’s Role in ZNE
While many people naturally assume the starting point to achieve ZNE is figuring out the type and size of renewables – such as photovoltaic panels, wind turbines or more exotic technologies – “The first, and maybe most critical, step in getting a building to net-zero energy use is to reduce its energy consumption,” said Doug Reimer, AIA, associate principal with Hennebery Eddy Architects in Portland, Oregon.

Given that heating and cooling account for one-third or more of total energy use in U.S. commercial buildings, according to the U.S. Energy Information Administration, getting to ZNE requires major focus on reducing these energy loads. As Reimer notes, a high-efficiency building envelope helps “to super insulate and reduce air leaks to stabilize the interior environment.  Then, fewer photovoltaic panels are required to generate energy to achieve net-zero.”

EnergyHigh-Efficiency Building Envelopes
To create ultra well-insulated and airtight buildings, more project teams are rethinking the envelope. Instead of attempting to make typical wall and roof assemblies more efficient, they are adopting tried-and-tested, though less common, high-efficiency envelop systems. Among these are structural insulated panels (SIPs).

SIPs are engineered wall and roof systems that combine structure, insulation and air barrier in one unit. The panels are made of a rigid insulating foam core to which structural wood panels have been laminated. Architects and contractors have successfully used SIPs for decades in a wide range of commercial and institutional buildings, including schools and hospitals, in climates ranging from sunny Southern California to the wet Pacific Northwest and frigid Alaska.

SIPs help create a high-performance building envelop by providing continuous insulation (ci) over a high percentage of the structure without having to add subsequent layers of insulation. Additionally, by having far fewer gaps to seal than other structural systems do, SIPs are much more airtight. Testing by the U.S. Dept. of Energy’s Oak Ridge National Laboratory (ORNL) showed that SIP structures are up to 15 times more airtight than stick framed walls insulated with fiberglass batts.

Because SIPs provide ci, reduce air leaks and help eliminate thermal bridges, they help lower energy costs for space heating and cooling by up to 60% above standards set forth in the 2015 International Energy Conservation Code (IECC).

Putting This into Practice – A Case Study
To help the Lake Washington School District in suburban Seattle advance its goal of being the most energy-efficient district in the state, the project team for the district’s Finn Hill Junior High set aggressive energy performance goals for the new school building. Designed to be zero net energy ready and 47% more energy efficient than targets set under the U.S. Department of Energy’s EnergyStar program, Mahlum Architects of Seattle specified 6-inch-thick SIP walls and 10-inch-thick SIP roof. The SIP-based wall assembly provides R-22 insulating power compared to R-10 for typical school construction in the region using 2×6 metal stud walls with R-19 batt insulation (the whole wall R-value of these walls is much lower than the insulation’s R-value, due to thermal bridges and air leakage).

The SIP panels help the school district reduce energy costs, and allow for smaller, more cost-effective mechanical systems. Reducing heating and cooling consumption was critical for the building’s ZNE-ready design, meaning that the potential area for the roof-mounted solar panels is sufficient to power all the school’s needs.

“Every aspect of the design and construction must be considered in an integrated way when energy conservation goals are so ambitious,” said Anjali Grant, AIA, LEED AP, project architect.

“Utilizing SIP panels not only supported the strategies for energy savings, it allowed for a smooth and rapid assembly process, shaving weeks off a tight construction schedule,” added Mitch Kent, AIA, project manager.

Opened in 2011, Finn Hill Junior High is a single-story, approximately 120,000-square-foot building replacing an existing school located on the same site. It was designed to serve 600 students, plus 150 students in an “Environmental Adventure School” located within the building. The school includes space for core academic instruction, special education, fine arts, technology, physical education, library and commons.

With ever-tightening energy codes, and building owners’ greater desire to lower energy costs, school and hospital teams increasingly will be challenged to provide ZNE facilities. Achieving ZNE requires careful attention to the building envelope. From Las Vegas to Los Banos and throughout the Western U.S., more schools and hospitals are relying on SIPs to lower energy consumption as a key step toward net zero.

Becky Susan is marketing manager for Premier SIPs.