900 LEE ST. E., Charleston, W.Va
RETROFIT TEAM
ARCHITECT AND MEP ENGINEER: Thrasher Group
OWNER AND GENERAL CONTRACTOR: AB Contracting
HVAC INSTALLER: Darnold Mechanical Inc.
HVAC DISTRIBUTOR: Ferguson Enterprises
MATERIALS
The following HVAC equipment was used in the building:
- Airstage VRF System
- CaptiveAire DOAS
THE RETROFIT
900 Lee St. E. is one of the tallest buildings in the capital city. AB Contracting Inc., a 100-person construction and property management company, acquired the 17-story building in April 2021 and immediately began creating a modern, mixed-use space in the circa-1960 high-rise. AB Contracting’s Founder Allen Bell’s vision included new office space on the lower floors with apartments occupying all levels above.
Architects and engineers at Thrasher Group redesigned the structure to serve its new purpose, as well as created plans for all MEP components. “The challenge on this project was converting old commercial space into modern, high-end apartments while converting the HVAC systems from a centralized system to something that could accommodate half-a-dozen zones per floor,” explains Thrasher Group’s Ken Smith, P.E., whose main focus was design of the new HVAC system. “Ultimately, a VRF system was specified for this reason, but other possibilities had been considered.”
“We decided on a VRF system because of its energy efficiency and the simplicity of creating many zones per floor across the 14 residential stories,” explains AB Contracting’s COO Brian Wadsworth. “Fujitsu’s Airstage line was selected because of their competitive package and the fantastic support we’d already received [from our Ferguson representatives].”
The tall, narrow building’s glass façade results in shifting solar loads and significant heat loss during the winter. As a result, most of the VRF equipment specified was heat-recovery units, providing the ability to reclaim energy where heat is being rejected and sharing it with zones calling for heat.
“We’re applying for state and federal historic tax credits for the work on this property,” Wadsworth notes. “This prohibits us from tinting the windows to reduce solar gain. As a result, the heat-recovery component is critical.”
Thrasher Group’s design included 278 tons of heat-recovery capacity with an additional 80 tons of heat-pump capacity. The latter was used almost exclusively throughout common areas in the lower commercial floors.
The building’s floorplan is served by a variety of terminal unit types. Slim-duct air handlers were installed in corridors and smaller apartments while a combination of medium- and high-static units were installed in larger apartments. High-static ducted air handlers were used in the atrium, offices and basement.
“Physical constraints were big drivers of design,” Smith says. “Vertical separation was the primary constraint, and we cleared this hurdle by splitting the 42 condensers between two farms; one on the main roof and one on the fourth-story mezzanine roof between the parking deck and main building.”
After the installation began, AB Contracting made an additional request for an IAQ package. A CaptiveAire 100 percent DOAS makeup-air unit was installed for the commercial floors. Separate ductwork ties to the returns on each VRF head.
With assistance from Ferguson’s VRF division, Darnold Mechanical installed and commissioned the systems between December 2021 and August 2022. Data captured during commissioning was sent to Fujitsu for review. Fujitsu’s System Controller also is being used to remotely monitor the VRF system.
PHOTOS: FUJITSU
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