Often, architects find themselves trying to convince owners to incorporate sustainable-design elements into their projects. But it can be equally challenging to work with an owner on the other side of the spectrum. When it comes to green, it may be hard to find a customer more knowledgeable and more demanding than the Department of Energy’s National Renewable Energy Laboratory (NREL) in Golden, Colo. NREL’s mission is to develop renewable-energy and energy-efficiency technologies and practices, and advance science and engineering to address the nation’s energy and environmental goals.
When the request for proposal went out seeking design/build teams for DOE’s new Research Support Facilities building, Denver-based design firm RNL and its design/build partner, Centennial, Colo.–based Haselden Construction, jumped at the opportunity. Rather than be frightened off by such a knowledgeable and demanding client, the design team, which had worked with NREL in the past, was very enthusiastic about the prospect of undertaking a project that aspired to achieve such lofty goals.
“It’s NREL, so you know it’s going to be a very energy-conscious, sustainably oriented building,” says Phil Macey, RNL’s project manager on the Research Support Facilities project. “We read the RFP and saw the hope was to create a net-zero energy building; that just lit us up. You might never convince a client to consider that idea, unless it’s someone as innovative as NREL.”
Slated to open in 2010, the Research Support Facilities are part of NREL’s campus in Golden, Colo. Currently, the organization leases office space outside the campus, so the new facility presents an opportunity for NREL move all of its staff to a central location and provide them a healthy, comfortable workplace.
Daylighting, natural ventilation, renewable energy, water conservation, and very ambitious energy targets all are part of the equation. “NREL built its own energy model based on its own extensive research and experience to determine how low it could go with energy use,” Macey says. “That number, which is 50 percent better than current standards set by the [Atlanta-based] American Society of Heating, Refrigerating and Air-Conditioning Engineers, became the contractual energy performance requirement of the design/build team.”
With the new facility, NREL and DOE seek to demonstrate a new paradigm in commercial construction. “The systems and approaches need to be commercially transferable,” Macey says. “DOE’s goal is for this to be an early prototype toward a goal of commercially viable net-zero energy buildings by 2025.”
Lighting the Way
One of the first steps in any project that aspires to result in net-zero energy is to maximize available free energy. By properly orienting and constructing a building, it is possible to harvest the energy of the climate and drive down a structure’s energy demand.
Achieving the daylight credit from the U.S. Green Building Council’s LEED certification was written into the RFP. Along with generating potential energy savings, well-planned daylighting and views help create a pleasant atmosphere for occupants. “Sustainability really is about people,” says Tom Hootman, director of sustainability at RNL. “This building, with all its technologies and strategies, ultimately is about energizing the workplace and the people in it.”
“Hypothetically, the most energy-efficient thing in the world could be to design a building with no windows, but who wants that?” Macey points out. “There has to be some joy. One of the big challenges was to find a way to get just the right amount of daylight into the building so the facility is naturally lit. It’s also designed so that no point in the building is more than 30 feet (9 m) from a window.”
Getting the right daylight balance isn’t as easy as installing a lot of windows. The type of light needs to be considered—the sun in Colorado is very direct and harsh—as does the issue of interior heat gain. “The building is fairly slim, which allows us to bring daylight in. Windows are sized to get just the right amount of daylight without overheating the space,” Macey explains. “And everyone has views. The partition heights are low so we can bring daylight all the way across a 60-foot (18-m) cross section.”
Control of potentially strong natural light is addressed through the use of a carefully tuned window system that includes separate daylight windows above vision windows. Each section includes glass types selected for heat-loss control and visible-light transmission. A fixed-light louver in the daylight window reflects sunlight to the ceiling, creating an indirect lighting effect. Fixed sunshades limit excess light and glare on the exterior of the windows so no workstation experiences glare.
The building is designed without a forced-air system. San Francisco–based Stantec Consulting, the project’s mechanical/electrical/plumbing engineer and energy consultant, has created an HVAC system with greatly reduced fan energy consumption. Radiant slabs provide heating and cooling and an underfloor air distribution (UFAD) system provides ventilation air. Because this UFAD only supplies tempered ventilation air, the raised floor height is just 12 inches (305 mm), considerably less than a typical UFAD application.
Exposed thermal mass surfaces in the interior of the building store excess heat over the course of summer days, reducing the cooling load. The heat from the data center is transferred to an underground crawlspace that contains a concrete labyrinth which acts as a remote thermal battery for the building. “Imagine if you took your two hands and interlaced your fingers,” Macey explains. “That’s how the structure looks.”
When interior temperatures exceed 70 F (21 C) at night, automatic operable windows open to purge excess heat. During the night, the thermal mass cools in order to store heat during the next day. In winter, heat enters the building in the latter part of day. As the environment starts to cool down and the building would likewise want to cool down, the heat will transfer to the interior to maintain its temperature overnight. In the summer months, the process can reverse. One-third of the operable windows are controlled by the building. Windows open at night, flushing air through the building to cool down the interior.
A somewhat low-tech approach is used in winter, using transpired solar collectors, an innovation NREL developed about 15 years ago. Although the name sounds complex, they are about as simple a device as one can imagine. “It’s a dark-colored piece of corrugated metal sheet siding with holes in it,” Hootman explains. “You put it on a south-facing exposure. The dark color heats up, perforations allow airflow through it, and it creates cavities of warm air against the building. We pull that warm air into the labyrinth during the winter and preheat the ventilation air.”
The underground concrete structure helps moderate the building’s temperature in any season. “For the majority of the year, we’ll be able to use outdoor air. In the warmer months, we’ll be able to use evaporative cooling,” Macey says. “For those extreme days, there’s the capacity to use conventional air conditioning as need requires.”
Focusing on the Details
The attention being given to light and temperature is only part of the total equation. Photovoltaic solar cells cover the roof and will supply the building with much of the energy it needs. A planned PV system will be integrated into shading structures over the RSF’s parking lot, as well. The total PV system size planned for the project is just under 1.4 megawatts. If the building performs as predicted by the energy model, this will create enough on-site renewable energy to make the Research Support Facilities a net-zero energy building over the course of a year.
Energy use is being modeled down to every last detail. “Every little thing you can imagine in a building has to be included in our energy model,” Hootman says. “That includes exit signs, emergency lights, and even the sump pump.”
“There’s a great deal of submetering being worked into the building,” Macey points out. “We’ll be going after the Measurement and Verification credit under LEED, which not many projects pursue. It’s a feisty credit because you just can’t fake it. The building will very much be a living laboratory for NREL.”
The plumbing fixture selection is projected to result in a 57 percent water use reduction over the minimum standards of the Energy Policy Act of 1992. The project’s landscape design uses a native prairie approach with efficient irrigation systems and climate responsive controls to dramatically reduce the use of potable water for irrigation. Due to Colorado water laws, the project is unable to incorporate any systems that involve rain harvesting.
There even is an interesting material reuse story. Columns for the vertical structure of the building are reclaimed natural gas pipes. According to Macey, the design team was drawn to this idea in part for the aesthetic of the perfectly round columns, but also because it represents a piece of the old energy system being integrated into a vision of a new energy system where buildings sustain themselves.
“I think we’re about to enter the future we’ve all been promised,” Macey says. “Buildings will be much more attuned to their environments. We’re turning an important corner. Whenever people ask when the new energy economy is going to happen, I say we’re in the turn now.”
Architect, interior designer, and landscape architect: RNL, Denver, www.rnldesign.com
Mechanical/electrical/plumbing engineer and sustainability consultant: Stantec Consulting, San Francisco, www.stantec.com
General contractor: Haselden Construction, Centennial, Colo., www.haselden.com
Structural engineer: KL&A, Golden, www.klaa.com
Daylighting: Architectural Energy Corp., Boulder, Colo., www.archenergy.com