It’s an engineer’s dream: A 220,000 square-foot office space designed with performance as the ultimate priority. Most building projects start in the mind of an architect and are then passed off to engineers, who have to figure out how to make the building function well, but the new net-zero National Renewable Energy Lab office building, in Golden, Colo., started with the engineering.
So it is that the building is a rather unusual “H” shape, with the lobby area connecting two wings, because the project’s engineers determined that shape would maximize daylight and thus reduce energy needs.
The building is meant to be a national showcase and a teaching tool, in addition to serving its primary function as office space for NREL.
“The overarching goal is to demonstrate that highly energy efficient and marketable net zero buildings can be built using available technologies and techniques today,” Jeff Baker, director of the Office of Laboratory Operations for the Office of Energy Efficiency and Renewable Energy’s (EERE) said during a webinar about the building’s technologies yesterday.
To do that, the team started with what they call a “performance-based” request for proposals that included three tiers of goals for the building. The first tier, or “mission critical” goals, included achieving LEED Platinum and Energy Star Plus standards. The second tier or “highly desirable goals,” included a wide range of elements from capacity for 800 staffers to creating an expandable building to using only 25,000 BTU per square foot per year. Net-zero energy was saved for tier 3, “If Possible” goals.
In order to get there, Baker says the team had a “manic focus on energy performance.” They also took a different approach to the RFP process. They started with a national design competition, sent out a draft RFP to the top three design teams, then collaborated with those teams to help hone the project’s goals and possible solutions.
The final RFP included a well-defined design-build strategy and conceptual designs, with a $200,000 stipend to defray conceptual design development costs. The result was multiple possible solutions and plenty of solid designs that the DOE now owns (the Department retained ownership of non-selected designs).
The strategy worked. The building achieves all three tiers of the goals set out for it, exceeding expectations in some areas. It accommodates 825 staff, is 50 percent more energy efficient than the most recent requirements from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), achieved LEED Platinum, and has what NREL calls Net-Zero Site Energy, which it achieves through the use of both energy efficiency and on-site renewable energy delivered via photovoltaic panels.
Defining Net Zero
The National Renewable Energy Lab has been careful in recent years to define net-zero appropriately. In a 2006 paper on the subject, a team of NREL scientists emphasized the importance of approaching net-zero via energy efficiency first, followed by renewable energy.
“A net zero energy building is a building with greatly reduced energy needs through efficiency gains such that the balance of the energy needs can be supplied by renewable technologies,” they write. “A good ZEB definition should first encourage energy efficiency, and then use renewable energy sources available on site. A building that buys all its energy from a wind farm or other central location has little incentive to reduce building loads.”
It’s a solid strategy and building the greenest office building in the country, and a net-zero building at that, can only be seen as success. But how replicable is it for designers and building owners who are not on the government’s payroll; people for whom the financial bottom line comes before proving that net-zero building can happen?
Given that the average square foot of office space in the Denver area where the NREL office is located runs about $140 per square foot to design and build, and the NREL building is $259 per square foot, there’s still progress to be made in terms of proving that net-zero can be achieved at an acceptable cost. Nonetheless, it’s extremely important that it has been done, according to USGBC LEED Senior Vice President, Scot Horst, and even more important that NREL plans to continue testing, tuning, and reporting back on the building’s performance.
The net-net of the net-zero experiment? All of the necessary technologies exist to achieve net-zero building today. The NREL building includes a mix of daylighting, shading, evaporative cooling, radiant floor heating, natural ventilation, underfloor air, thermal mass. Materials used include reclaimed natural gas pipelines used as structural columns. The building increases NREL’s campus square footage by 60 percent but only increases energy needs by 6 percent, and then fulfills those needs via a rooftop solar array. But paying for it all? The mechanics of that still need to be worked out.