Credit: Timothy Hursley
For the design of an eight-story General Services Administration office building just outside of Houston, the architects devised a double-wall system: exterior concrete walls with a curtainwall overlay with fritted glass panels that shield the building from the Texas sun.
Located in a suburb of Houston sits a commanding eight-story General Services Administration (GSA) office building conceived by a joint venture of the architecture firms Leo A Daly/LAN and PageSoutherlandPage. It was designed under the GSA's Design Excellence Program, which was instituted to attract talented architects and engineers to federal workspaces. This new 275,000-square-foot building incorporates security criteria and sustainability strategies into a singular building vision.
Since it is aiming for LEED certification, the primary design goals were to reduce energy costs, bring daylight into the interior, and providing views. To increase the penetration of natural light, the architects oriented the long, narrow building on an east-west axis, so that the longer elevations face to the north and south. This alignment allows daylight to reach the greatest percent of the building's interior.
The exterior walls are constructed out of poured-in-place reinforced concrete to meet security criteria, and the concrete doubles as a support system for a glass curtainwall. Conceived primarily to shade the sun, this outer membrane wraps the east, south, and west sides of the building and is made up of fritted glass panels that are offset from the concrete structure. To take full advantage of natural light, the north side is left bare.
The glass panels are spaced 1 inch apart and are attached with stainless steel clips to a metal frame that is secured to the concrete shell. Windows that are almost 9 feet tall are matched by openings in the glass skin, which are slightly smaller than the window dimensions to provide shading. The architects analyzed the sun angles so they could properly size the apertures and optimize the distance between the two skins. And in order to work as a screen, the glass panels were chosen to minimize transparency. Because the architects wanted the building exterior to blend with the lush suburban Houston landscape, a custom, green negative-dot ceramic frit was designed for the clear glass, making it almost opaque.
The quality of the interior light was extremely important to lead designer Lawrence Speck, a principal at PageSoutherlandPage. Speck's intention was to modulate the light to address the conditions in southern Texas, where the sun can be so bright that all one sees is glare. “To have a full [exterior] view with a halo of green around [the window] gives a nice graduation of light from inside to outside,” he says.
One of the main challenges, Speck explains, was how to lower the building's heat gain while still allowing in daylight. To help insulate the building from the sun and its heat, reflective aluminum shingles were applied to the exterior. The fritted-glass façade also serves as an insulating layer, and the gap between the glass and the aluminum skin creates a thermal stack effect, cooling the air temperature inside the building by 10 to 15 degrees Fahrenheit. A 30- to 50-percent energy savings is estimated by using a dual exoskeleton: It assists in moderating interior temperatures, thus reducing the building's total air-conditioning load.
Another benefit of the double façade is the play of light created by the green fritted glass and the aluminum cladding. Speck notes that it looks as though the structure “glows from inside” as the afternoon light dances across it.
Sustainable design concepts extend throughout the building site and landscape, and the orientation of the buildings allowed for the preservation of several stands of existing trees. Combined with additional landscaping, these trees provide for pleasant views from the inside and shading on the outside. Site topography, landscaping, and entrances and exits were all designed to decrease runoff and to meet the GSA's stringent security requirements.
The result of all this design and testing is a field office that successfully transitions the vertical boundary between interior and exterior.Details
Project: General Services Administration Regional Field Office, Houston, TexasManufacturers
Client: U.S. General Services Administration, Fort Worth, Texas
Architects: Leo A Daly/LAN+PageSoutherlandPage, A Joint Venture, Houston, Texas
Lighting Designer: Lesco Architectural Lighting, Houston, Texas
Project Size: 275,000 square feet
Energy code compliance: ASHRAE 90.1-2001 per LEED 2.1 requirement
Watts per Square Foot: a little less than 1
Curtainwall: Accura (windows); Berger Iron Works (metal frame supplier—exoskeleton); Haley-Greer (hardware supplier of stainless steel clips, also the glazing contractor); Viracon (fritted, laminated glass); USM (aluminum shingles)
Lighting: Bega, C.W. Cole & Co., Cooper Fail-safe, Dasal Industries, Designplan Lighting, Federal Signal Corp., Finelite, Focal Point, Gotham, Insite Lighting, Leucos, Lithonia Lighting, Osram Sylvania, Peerless Lighting, Philips, Philips Bodine, Philips Day-Brite, Philips Gardco, The Lighting Quotient, Thomas Lighting, Tre Ci Luce, Vision 3 Lighting, Zumtobel