The eco-roof is a pilot project for the city. A key to its realization was the city’s willingness to waive the requirement for conventional stormwater treatment measures so those funds instead could be directed toward the roof’s cost.
For years, one of the weak links in the green building chain has been the lack of post-occupancy evaluation. Although building owners and industry professionals are conducting more operational follow-ups to see if results actually meet predictions, the U.S. Environmental Protection Agency (EPA) is using its Region 8 Headquarters in Denver as a continuing opportunity to examine, demonstrate, and partner on sustainable initiatives.
Winner of a 2009 Evergreen Award in the Ecommercial category, the 292,000-square-foot Region 8 Headquarters leverages familiar high-performance strategies with innovation. The mixed-use building’s design strikes a balance between historic and modern, security and invitation, and necessity and inspiration.
Conceived as a build-to-lease project for the EPA, the project had to make sense from a market-rate standpoint for the building’s commercial developer. A reclaimed brownfield location adjacent to Union Station in lower downtown Denver’s highly valued historic district provided a multitude of alternative transportation options to serve the ecologically conscientious tenant. John Breshears, principal in the Portland, Ore., office of Zimmer Gunsul Frasca Architects (ZGF), selected exterior building materials such as brick, cast stone, unitized aluminum curtainwall, and high-performance glazing to deftly address the historic aesthetic yet offer modern appeal.
A 10-kW photovoltaic array produces the energy needed to run Region 8’s emergency response center program in the building.
Development rights on adjacent lots were sold but no one knew the exact details of the future build out. Breshears says the one certainty was an important park in the city’s master plan that would be located directly across the street from the Region 8 building. Modeling studies showed that two L-shaped building masses placed at 45 degrees to the cardinal compass points would capitalize on solar orientation for daylight and wind conditions for cooling. The masses form a large atrium at their center, which offers needed assembly space for the EPA’s region-wide meetings. The atrium also allows natural light to filter down through nine stories of deep office floor plates. “The atrium forms a ‘living room’ area for the EPA,” Breshears says, “and it corresponds to the open public space across the street, providing a counterpoint to the district’s intended park.”
Dan Heinfeld, Evergreen Awards judge and president of Irvine, Calif.–based architecture firm LPA, notes the atrium achieved multiple objectives. “This large office project is a good example of how sustainability can inform the design process. The use of the atrium to maximize daylighting and energy efficiency also creates a good neighbor that fits its historic downtown context with an appropriate scale and streetscape.”
In the office areas, exterior shading elements, interior light shelves, and a combination of automated and manually operated blinds manage sunlight, glare, and heat gain. An integrated lighting control system captures the energy savings from these strategies.
Raising the Sail
The solution for controlling light at the top of the atrium was not readily apparent, so Breshears deferred the task in the design process. He knew he wanted to bounce sunlight down to the atrium floor, but needed to protect office occupants from glare along the way. As construction progressed, the decision became clear. Computer-generated and physical models indicated that a series of elliptical reflectors would work, but finding the right material within the budget proved elusive.
Ingenuity led the team to some nautical sail makers in the Portland area, and the parabolic “sails” were cut from canvas. ZGF used in-house software to create a pattern for the custom fabricated sails, and a theatrical rigging company in Denver performed the installation. The turnkey solution for the contractor became a visible example of an innovative and inexpensive sustainable design feature.
The ZGF team created a tailored shading plan for the L-shaped masses. Exterior horizontal shades and an interior light shelf with automated horizontal blinds in the daylighting zone manage the direct sunlight in the building’s south portion. On the north wing, the exterior shading elements and interior blinds are vertical in orientation to diffuse northern light. Lighting controls measure the amount of daylight present and dim electric lights accordingly to reduce energy consumption. ZGF and the Center for the Built Environment (CBE) at University of California, Berkeley, conducted a post-occupancy evaluation that showed occupants found the daylighting and lighting control strategies to be successful.
Careful material selection, orientation and tailored shading strategies integrate the project into Denver’s historic context and create an energy-efficient envelope. The façade employs two distinct strategies. A sunward system shades the glazing and controls direct sunlight on 45-degree aspects, while a windward system gathers light from the clear north sky and prevents glare from the low-angle summer sun season.
An efficient HVAC system with underfloor air distribution (UFAD) provides needed ventilation, as security requirements preclude operable windows. The CBE conducted extensive testing and system commissioning on the Region 8 Headquarters UFAD system. The combination of good design and careful plenum construction ranked it as one of the best performing systems of its type in the nation.
A concrete frame structure meets the General Services Administration’s security criteria and the added mass provides nighttime air flushing to lower the building’s daily heat gain.
A 48-panel, 10-kW photovolatic array on the rooftop also saves energy. Operational data reveals that the combined measures help the facility perform 40 percent better than a baseline building.
The windward side of the Region 8 Headquarters has nine floors, but the sun-facing side has eight. On top of the sunward building wing, a roof terrace oasis sheltered from the wind overlooks part of a milestone project for Denver—a vegetated green roof that provides stormwater management. The city of Denver mandates that developers provide a structure to filter and clean stormwater runoff and release it slowly into the city system. Convincing the municipality that an eco-roof could meet this requirement was a significant effort. To make the roof financially feasible for the private developer, it was critical that the standard stormwater requirements and their associated costs be waived. The team provided documented evidence and formal testimony from national and international experts, and the city and county of Denver approved the eco-roof as a pilot project.
The Region 8 building touts Denver’s first eco-roof designed specifically to treat stormwater. Its performance is being analyzed by a consortium of experts from the EPA, the city of Denver, the Department of Horticulture at Colorado State University, and the Denver Botanic Gardens.
The EPA and city are measuring and testing the roof’s effectiveness. The aridity, wind, and lack of precipitation in Denver also pose problems to maintaining vegetation on an eco-roof. The EPA formed a coalition with the Department of Horticulture and Landscape Architecture at Colorado State University and the Denver Botanic Gardens to breed new and appropriate plant species and examine soil media compositions. The Region 8 project already has spurred recent measures to evaluate green roofs for future stormwater management in Denver. In addition to the stormwater benefits, vegetated roofs reduce the urban heat island effect and create habitat. The coalition’s continued exploration into plant and soil media offers new prospects for eco-roofs in similar climatic regions.
After more than two years of occupancy, the EPA is still gathering data on its LEED Gold–certified building and opening its doors for studies. The agency leads environmental science, research, education, and assessment efforts, and the Region 8 Headquarters is helping it achieve its goals.
“The EPA is an incredibly enthusiastic client. They’ve created tours, brochures, and promotional pieces on the building and are committed to ongoing investigation of the systems and strategies there,” explains Breshears.
Two L-shaped building masses surround a central atrium that brings natural light deep into the nine-story office space and provides a gathering space for EPA employees and the public. Innovative parabolic canvas reflector “sails” at the top of the atrium direct and buffer the light to prevent glare. The sails were fabricated from the same type of canvas used in boat sails.
Design architect, landscape architect: Zimmer Gunsul Frasca Architects, zgf.com
Architect of record: Opus A&E, opuscorp.com
Associate architect:Shears Adkins Architects, shearsadkins.com
Interior designer: Metropolitan Architects & Planners, metroarch.com
Client/owner: General Services Administration on behalf of the U.S. Environmental Protection Agency, gsa.gov
Structural engineer: KPFF Consulting Engineers, kpff.com
Engineer of record: Syska Hennessy Group, syska.com
Mechanical engineer: Doyle Engineering
Electrical engineer: BCER Engineering, bcer.com
Civil engineer: Martin/Martin Consulting Engineers, martinmartin.com
Construction manager, general contractor: Opus Northwest, opuscorp.com
Lighting designer: Keylight + Shadow
Green consultant, LEED consultant and/or life-cycle performance partner: ZGF (design phase); Architectural Energy Corp. (submittals phase), archenergy.com
Photographs: Robert Canfield
Materials and Sources
Building management systems and services: Alerton, alerton.com
Carpet: C&A, tandus.com; Interface, interfaceglobal.com; Shaw, shawfloors.com
Ceilings: Armstrong, armstrong.com
Flooring: Forbo Flooring Systems, forbo.com; Natural Cork; Atmosphere Recycled Rubber, tomkt.com; Johnsonite, johnsonite.com; Daltile, daltile.com; Precast Terrazzo
Furniture: Herman Miller, hermanmiller.com
Glass: Al Glass, alglassandmirror.com (curtainwall)
Lighting: Ledalite, ledalite.com; Portfolio, portfolio-lighting.com; Edison Price, epl.com; Lightolier, lightolier.com; Translite Sonoma, translite.com
Masonry: Norstone, norstone.com
Millwork: Renewed Materials; DecoMetal, Formica, formica.com; Icestone, icestone.biz; Wilsonart, wilsonart.com; Nevamar, nevamar.com; Lamin-Art, laminart.com
Paints and finishes: Benjamin Moore, benjaminmoore.com; Zolatone, zolatone.com
Photovoltaics: Namasté, namastesolar.com
Plumbing and water systems: Zurn, zurn.com; Falcon, falconplumbing.net
Roofing: Firestone Building Products, firestonebpco.com
Wallcoverings: Carnegie, carnegiefabrics.com; Maharam, maharam.com; Herman Miller; Interface; Designtex, designtex.com; Innovations, innovationsusa.com; Wolf-Gordon, wolf-gordon.com
Windows, curtainwalls, doors: Viracon, viracon.com; Gardner Metal Systems, gardnermetal.com; VT Industries, vtindustries.com; Greencore
KJ Fields writes about architecture and sustainability from Portland, Ore.