©2013 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 55, no. 9, September 2013.
By Chuck-Kwan Joseph Tai, P.E., P.Eng., Member ASHRAE; Matt Grinberg, P.E., Associate Member ASHRAE; Porus Antia, Member ASHRAE
About the Authors
Chuck-Kwan Joseph Tai, P.E., P.Eng., is senior associate at Stantec Consulting, Inc. He was engineer of record and project manager of the NREL Research Support Facility. Matt Grinberg, P.E., is a mechanical engineer, and Porus Antia is building simulation - project manager, Stantec Consulting, Inc. Grinberg and Antia are ASHRAE certified Building Energy Modeling Professionals.
The world’s largest net zero energy building did not happen overnight, but it did start with an ambitious vision. When our team first pursued the design of a new Research Support Facility (RSF) at the National Renewable Energy Laboratory (NREL) in 2008, the stipulated objective in the request for proposal (RFP) was an annual energy consumption of 25 kBtu/ft2 (79 kWh/m2).
Rather than just meeting this aggressive requirement, we submitted a plan to deliver what NREL had on their wish list, a building that would use as much energy as it would produce—a net zero design. The idea was we could do this within a typical design-build (DB) schedule and a rigid $64.3 million cost budget.
Once the design target was set, our team, consisting of Haselden Construction, Rogers Nagel Langhart (RNL) Design, and Stantec Consulting, launched into action with a course focusing on passive architecture, energy-efficient building systems, and renewable energy. The result is a new 222,000 ft2 (20 624 m2) office building constructed on the NREL campus in Golden, Colo., that includes open and private offices, conference areas, a lunch room, a data center, as well as a fitness area and a library.
Setup for Success
Even though all the individual technologies have been used before, the innovation in this project is how they are integrated. The design is tuned to maximize passive architectural strategies, taking advantage of the climate to drive energy use reduction. We performed extensive modeling evaluations to come up with the narrow floor plate and slanted H-shape of the building for optimal energy performance. The site orientation, plan, section, massing, and the envelope design all work to provide ample daylight and naturally ventilate the building. The narrow floor plate allows single-sided and cross-ventilation strategies to naturally ventilate the building. No employee is more than 30 ft (9 m) from an operable window and all working spaces are designed for natural, passive cooling. Modeling was instrumental in determining the quantity, dimensions, and location of windows to properly balance daylighting and load reductions. We designed aggressive window shading to address different orientations and positions of glazed openings, and employed special glazing such as electrochromic windows. This effectively reduces heat gain during the summer while still providing daylighting.
The building architecture also preheats its own ventilation air, and its exposed thermal mass and remote thermal labyrinth allow the building to store its own thermal energy. Using an insulated precast concrete panel system, our team designed thermal mass that is exposed to the building interior, allowing effective nighttime cooling. The below grade labyrinth of heavy concrete structures is built in the crawlspace of the building. This labyrinth stores thermal energy and provides additional capacity for passive heating and cooling of the building. Even the roof of the building tilts gently to the south to enhance energy generation from a roof-mounted photovoltaic (PV) system.
Integration and Process
Achieving net zero requires optimization and integration of all the energy flows and systems in the building. In this regard, we made extensive efforts to reduce energy requirements of the information technology (IT) systems. A reduction in stand-alone printers and copiers, for example, reduces energy demands without compromising productivity. Similarly, we phased out stand-alone computers for either laptops or thin client machines.
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