GPI/Greenman-Pedersen Inc.: Bechtel Reston

Existing building retrofit at an office building.

By GPI/Greenman-Pedersen Inc. August 14, 2014

Engineering firm: GPI/Greenman-Pedersen Inc.
2014 MEP Giants rank: 62
Project: Bechtel Reston
Address: Reston, Va., U.S.
Building type: Office building
Project type: Existing building retrofit
Engineering services: Electrical/power, HVAC/mechanical, lighting, energy/sustainability, and plumbing/piping
Project timeline: 1/9/2012 to 12/13/2013
MEP/FP budget: $270,000


GPI provided mechanical, electrical, plumbing, and fire protection design services for the 188,000-sq-ft new offices in Reston, Va. GPI worked closely with Hickok Cole Architects. Bechtel occupies space in two buildings. Building 1 includes 112,000 sq ft of office space plus a 5,000-sq-ft conference center; Building 2 includes 71,000 sq ft of office space. The office space includes a mix of offices and workstations along with standard support areas, pantries, storage, conference rooms, small sensitive compartmented information facility (SCIF) area, and intermediate distribution frame/main distribution frame (IDF/MDF) rooms. The project earned LEED Silver certification and won the 2013 NAIOP Northern Virginia Best Interiors for Tenant Space 50,000 SF and Above Award of Excellence. Engineering challenges the design team faced included surveying occupied office space, phasing of demolition and new work to accommodate partially occupied spaces, coordinating low plenum clearances with new work, multiple IDF and server room designs, and providing cooling/heating to accommodate high-density conference rooms.


The challenge of surveying occupied office space required visiting the site during off hours to verify existing conditions and coordinating access to some sensitive areas. The design team met this challenge with a team coordinated effort. The result was a well-coordinated design set. Portions of the second floor were required to remain in operation during the demolition and new work schedule. This presented some challenges in meeting the construction schedule. For this reason the design team produced phasing documents that governed the MEP work associated with performing demolition and new work so as to ensure minimum downtime of the current tenant. Temporary ductwork, variable air volume (VAV) boxes, and power were provided to keep existing systems functioning. In addition, the permitting of this portion of the project was phased as well. This included carefully representing existing and new work scopes of each phase in a manner that communicated the intent of the phasing work. As with many of the older facilities in the region, low plenum heights present a challenge. In this case, 24 ft was the maximum existing ceiling height. The firm was tasked with coordinating new work with limited plenum clearances while attempting to maximize ceiling heights in the conference rooms. This resulted in modifying and rerouting significant portions of existing ductwork to accommodate the ceiling heights. Also, care was taken to route sanitary piping to accommodate the ceiling heights. IDF rooms were designed for five floors in Building 1 and the server rooms of the 7th and 8th floors. This required designing exhaust/makeup air for the IDF rooms, and in some cases cooling units for rooms with larger loads. The loads in the server rooms required a new dedicated glycol-cooled system, which included floor-mounted units, a roof-mounted dry cooler, and duplex pump package sized for the load. Floor-mounted units were used to accommodate the low plenum heights. The routing of glycol piping up through multiple floors, and offset on the top floor, was carefully coordinated to eliminate conflicts with existing facilities. Owing to the fact that some of the conference rooms would function after hours and the client required a system to provide cooling in high-density areas, supplemental units were included. This required selecting units with low profiles that would fit above the limited ceiling space. Also, the units were sequenced to function simultaneously with VAV boxes to provide the code required ventilation rates. Although these circumstances presented a challenge, GPI’s efforts, in concert with those of Hickok Cole Architects, Bechtel, and other consultants, resulted in challenges met and solutions presented to satisfy the client’s needs.