From the Design Quarterly: Looking back on the first large-scale net zero energy building
April 14, 2020
What the successes of the National Renewable Energy Laboratory research facility say about striving for zero today
This article first appeared as ¡°First large-scale net zero energy building¡± in the Â鶹´«Ã½ Design Quarterly, Issue 06.
In 2007, when the?National Renewable Energy Laboratory?(NREL) in Golden, Colorado, issued a design competition for a new 222,000-square-foot research support facility (RSF), it wanted to make a splash in the industry. The U.S. Department of Energy, which runs NREL as a?national laboratory, wanted to show that ultra-energy-efficient buildings were achievable. The project¡¯s requirements were highly researched and written in detail with requirements ranging from ¡°mission critical¡± to ¡°blue sky¡± or ¡°if possible.¡± It specified LEED Platinum as a requirement, but the project aspired to be net zero energy, a certification that didn¡¯t exist at the time.
NREL¡¯s mission was to prove how its own research on energy efficiency, commercial building technology, and renewable energy could be translated to viable commercial properties within a reasonable budget. The building competition came with a $65 million budget and a stringent mix of requirements in energy, sustainability, safety, and design-build process¡ªits energy use would be offset by a renewable system. There were no prototypes for the building NREL envisioned, it would be the first of its kind.
The design-build team, led by Â鶹´«Ã½ as architect and mechanical-systems designer, had experience building smaller net zero energy and LEED-Platinum facilities up to 40,000 SF in the US. To win the competition, the team had to scale up its ideas and approaches in order to deliver NREL everything it specified, not just the essentials. To win the project, we implemented a range of strategies and in doing so, created a model for the largest net zero energy building in the nation¡ªon a budget. The result? An iconic building which sparked the net zero design movement, one that today¡ªalmost 10 years after opening day¡ªstill shines a light on the what¡¯s possible with high-performance, sustainable design.
Completed in June 2010, the NREL RSF-I is home to approximately 800 Department of Energy and NREL administrative staff.
How did it happen?
The?National Renewable Energy Laboratory Research Support Facility?in Golden, Colorado, opened in 2010.
Ambitious but clear goals and an integrated team
As an organization focused in the field of building energy performance, NREL had the detailed knowledge and research to target and specify a clear energy utilization intensity goal for its new building. They knew what they wanted and knew it was possible.
The highly researched targets resulted in a specific goal. The original target of 25 KBTU per square foot was adjusted to 35 KBTU per square foot to include the energy use of a 2,000-person data center. That was an extraordinary target for a building at that time.
NREL mandated several critical inputs that influenced the building¡¯s energy appetite and created the basis for the performance-based energy model. We committed to meeting every one of NREL¡¯s challenging mission critical, highly desirable and if-possible objectives as a strategy to win the project. NREL insisted that delivery come from an integrated team of architects, engineers, and builders so that everyone involved, from day one, understood the project goals and strategies. Maintaining that integrated team communication around a given solution was a huge part of what set this project up for success.
Architectural solutions and strategies
Our solution to the goals set out in the design competition¡ªwhich required a 90% daylit building¡ªwas to design a form and shape of the building that could maximize daylighting.?
As an organization focused in the field of building energy performance, NREL had the detailed knowledge and research to target and specify a clear energy utilization intensity goal for its new building.
We chose an H-shaped building with narrow 60-foot wide floor plates, which enabled us to use natural daylight but also to naturally ventilate the space. That¡¯s just one of the architectural and passive strategies we employed to achieve efficiency¡ªbefore any mechanical or renewable systems were selected.
The two long wings of the H-shaped building stay cool in warmer months due to the internal facing thermal mass in the walls, not unlike the cathedrals of Europe. Continuous insulation and extensive exterior window shading further contribute to an envelope-driven, low-energy building performance strategy.
When we realized that the site had expansive soil and would require a raft slab, we proposed an underground thermal labyrinth that could be used to preheat or precool the air for the building at minimum additional cost. Further strategies employed included orienting the building to the path of the sun to reduce heat gain and enhance daylighting, making sure there was no thermal bridging and utilizing triple-pane windows, evaporative underfloor cooling, radiant ceilings, natural ventilation, and night venting. We utilized a transpired solar collector on the south fa?ade to make hot air and release it to the labyrinth to preheat the building. We did something similar with the hot air from the data center, containing it and dumping it into the labyrinth to use for preheating the building.
Natural daylight flows into the NREL research facility¡ªwith 90% of the building daylit without large glass openings.
Natural daylight, natural ventilation by design
With our narrow floor plates, we could naturally cross-ventilate by using an operable window system. Windows were comprised of a vision window and daylighting window, which incorporated a light louver system that could project light 14 feet deep into the space per vertical foot of light louver installed. That¡¯s how we daylit 90% of the building without turning to large glass openings, which would have detracted from the insulation needs of our high-performance envelope. We daylit 90% of the building while achieving a 28% window-to-wall ratio.
Serious goals, serious stakes
One key to our success was modeling the project as accurately as possible, to ensure that we could hit our targets during both design and construction. NREL was so serious about hitting net zero energy, that it tied financial incentives to achieving energy goals in each phase. In fact, if we couldn¡¯t demonstrate that we were on target in the early months to hit the goals we promised in the design competition phase, then a contractual mechanism allowed the design-build team and client to part ways.
Those targets were paramount to NREL, because they wanted to use this building as an example for the entire industry, to show it how to achieve net zero energy at cost comparable to conventional.
A second opportunity
The resulting RSF-I building was the demonstration center that NREL envisioned. In fact, the client was so happy they asked us to do it again. The same design-build team was asked to design and construct a 110,000-SF addition (NREL RSF-II) to the campus. For RSF-II, we were able to apply some lessons learned from RSF-I.
For example, we found that we didn¡¯t need concrete partitions in our thermal labyrinth because there was enough thermal mass in the raft slab and basement walls for thermal storage. We also realized we could reduce the window frame area by using larger operable windows. And we discovered we could naturally ventilate the stairwells instead of using active cooling. But probably the most rewarding discovery was that we¡¯d done very well the first time around.
Annual energy use has been tracked at the NREL facility against energy models, and it consistently falls within 5-10% of predictions.
A long-term commitment
NREL RSF-I was conceived as a living laboratory. NREL planned to write dozens of scientific research papers on the building and its performance, so it has made investigating and tracking a zero-energy building¡¯s operational energy performance a priority. In fact, the building monitors its energy use and production, light levels and water usage, and displays the data in the building lobby.
Through a close connection with NREL¡¯s Shanti Pless, I was able to remain in the loop on the measurement and verification stage of the building long after the design-build team had left the site. It was important for Â鶹´«Ã½, as a consulting firm, to stay connected with the operational side of a zero-energy building and access performance data to confirm that the targets we set during design were met. This is key to the reputation and success of our ongoing building performance and sustainable design practice.
Proven net zero
Annual energy use has been tracked against our energy model since the building opened in 2010, and it consistently falls within 5-10% of predictions, which sets a high standard for the industry. NREL is applying for the new LEED Zero certification with the U.S. Green Building Council that addresses net zero operations and resources in building.
NREL RSF I&II succeeded because it was driven by a committed and educated client who wanted to create a truly replicable strategy for NZE buildings and a truly integrated team that focused on the little details with the big picture project goals in mind. We know it succeeded because of the extensive post-occupancy focus on zero energy operations.
Today, net zero is no longer a novelty, yet we still have a long way to go move beyond what we designed for NREL across our built environment. Now we know what¡¯s possible when we strive for zero.