The Washington, D.C. headquarters of the National Association of Realtors was the first building within the District of Columbia to receive certification from the U.S. Green Buildings Council’s LEED rating program. Today it also houses the Portland Cement Association’s Washington office. The 102,000-square-foot, 12-story structure achieved this honor through a variety of innovative features, including an efficient HVAC system and glass curtain wall that reduce energy use by up to 30 percent, the elimination of CFC refrigerants, and the use of a carbon dioxide monitoring system.

Achieving such an environmentally-sound structure was no easy feat, particularly because the construction site, which had formerly housed a gas station, was plagued by contaminated soil. In fact, more than 24 feet of soil had to be excavated and disposed of before construction could begin. In addition, the geometry of the triangular site (located three blocks from the Capitol at the intersection of a diagonal street) called for an original approach to the building’s design and construction.

Concrete provided the solution to many of these dilemmas. A concrete frame allowed the building to be constructed within the restricted space. Concrete floor slabs also provided the means to achieve the architect’s vision for the structure’s curved-glass façade, a design that necessitated minimal deflections. To minimize the effect of concrete creep, the design incorporated post-tensioning, ensuring that after the spans shortened and the creep caused the concrete to deflect and uplift, long-term deflection was nonexistent. The water/cement ratio of the 5,000-psi concrete also was restricted in order to control creep. The concrete contained corrosion additives to prevent damage to the reinforcing steel.

Some of the structure’s other design specifications also presented challenges. The architect called for a minimal number of columns, so post-tensioning was used in select areas in order to create larger spans. The recessed edge of the slab at the second floor required the design of intricate brackets behind the columns, which enabled the design team to have the columns flying in front of the supported second floor plate, almost as if the floor was floating in the air behind them. The slab thickness is 14-inches at the edge drops and 8-inches inside, while the columns are 24-inches round.

Construction on the $46.5-million design-build project began in October 2002, and the National Association of Realtors moved in to occupy five of the building’s floors in May 2004. Since its completion, the green structure has received several accolades—the Washington Business Journal credited it with best architecture and best financing, and it was a runner-up for best urban office project and best sustainable growth project.

Project Summary

Owner/Developer: National Association of Realtors

Architect/Interior Architect: Gund Partnership

Architect of Record: SMB Architects -- Stephen M. Banigan

Structural Engineer: Fernandez & Associates

Developer/Builder: Lawrence N. Brandt, Inc.

Construction Manager: Carr America Development

Concrete Contractor: Miller and Long

Post-Tension Supplier: Suncoast Post-Tension, L.P