HVAC Repair

Building 3136 is located at Davison Army Airfield (DAAF) at 6970 Britten Drive, Fort Belvoir, VA 22060 and is the airfield operation center. It will remain occupied and mission ready throughout the completion of the construction. Contractor shall provide a temporary conditioned work facility on site, large enough to support a minimum of 10-15 employees, for swing space while work is underway within the office space. The building footprint is approximately 12,060 gross square feet, including two floors of offices, a control tower and a below grade mechanical room. B3136 was constructed in 1966 but has been renovated since then. The existing 2-pipe fan coil system is approaching 30 years old and has antiquated controls. The air-cooled chiller located outside mechanical room operates on R-20 refrigerant and leading to increased difficulty maintaining the system. The offices are heated by wall fan coil units and cooled by window mounted air conditioners. The server/IT room is cooled by Liebert unit separated the rest of building. The heating water is provided by the condensing boiler with BAS controls resided in the mechanical room which is not working properly. B3136 is an aging building showing signs of deferred maintenance. This existing configuration has led to difficulty maintaining comfort cooling or heating. The two-story portion of the building is constructed with concrete masonry units (CMU) and has a low-slope gabled roof with a modified bitumen roof finish. Large windows with a small sliding operable sashes are placed on a 2-0 knee-wall and extend to the finished ceiling in office spaces. The penthouse has a steel frame with curtain walls consisting of aluminum spandrel panels and fixed, insulated glazing. The penthouse has a minimally-sloped, flat roof with a modified bitumen roof finish. The mechanical room is located below grade at the south end of the building. The rest of the building has a large crawl space (approximately 4 in height) below the concrete floor of the first floor. The first floor has a concrete floor that is approximately 5 (F.V.) thick. The second floor is supported by steel bar joists with corrugated steel decking and a concrete floor. The roof has a steel bar joists with a poured gypsum deck (F.V.). The second floor joists have an approximate clear space of 13 (F.V.) and the roof joists have an approximate clear space of 13 at the eaves and 22 at the peak of the roof. Fixed portions of windows have insulated glass with the bottom quarter of the windows having an operable sliding sash. Some sashes have been removed to install window AC units. Windows appear to be in fair condition. This project addresses the inadequate HVAC configuration. Due to the limitations of the building construction, the HVAC shall be replaced in-kind including but not limited to, 2-pipe fan coil units, air cooled chiller, new insulated piping, circulator pumps, boiler, and valves. Additional fan coils are desired in the hallways and offices that are currently not served by the existing piping if feasible. The replacement system shall provide wall-mounted digital thermostat read outs for each fan coil showing the temperature set-point allowing for clearer understanding of system function to end-user. The building is to remain operational during construction.