The Vision of an Efficient HVAC System
An efficient HVAC system is designed to deliver the best quality thermal comfort and indoor environmental conditions, while minimizing energy consumption. Local regulations are increasingly requiring more efficient and integrated building systems, especially in Washington, DC, where an unprecedented DC Green Code will soon be implemented.
When designing Co|Lab’s MEP system, we partnered with Staengl Engineering to achieve an integrated building system. Staengl was an ideal partner because of their approach to system impacts on human health and their established partnership with the building architect William McDonough + Partners. We felt it was critical that the MEP engineer be a partner who embraced our overall vision for the project and holistically design a systems approach.
In seeking to achieve net zero, the system design is a crucial decision with little room for error. We initially considered a ground source heat pump, but with less than 9,000 square feet to manage, a variable refrigerant flow (VRF) system proved the best approach. By using a VRF, the square footage of the rooftop solar arrays was increased, helping to achieve net-zero operations.
The VRF system is a semi-centralized version of a traditional heat pump system, leveraging localized fan coil units (FCU) to create multizone systems. The system can shift heat from one zone to another. For example, if the conference room is used for a meeting on a cool day, excess heat from the conference room occupants will be recycled to provide heating for the mockup bays. The VRF system provides excellent efficiency and flexibility at a reasonable cost for light-commercial buildings. An independent, dedicated ventilation system provides a continuous supply of fresh air to the building spaces utilizing energy recovery ventilators (ERVs). The ventilation system is controlled to deliver fresh air to occupants based on measured CO2 levels in the building spaces. The building air delivery system is designed to provide balanced airflow to all conditioned spaces, and inter-zonal air pressure differences should be limited to three pascals.
The next level of the Co|Lab MEP approach is radiant heat flooring. This hydronic system uses liquid in a closed loop recirculating system, which flows through the floor of the mockup bays in a tubed system for efficient and consistent warmth radiating from the mockup bay flooring. The mockup bay can be kept comfortable for the occupants, while the air temperature is lower, helping to conserve energy.
The radiant heating water is generated by the VRF system, taking advantage of high-efficiency heat pump heating and waste heat from cooling, when available. The hot water system also provides pre-heat for the buildings domestic hot water, further utilizing waste heat from cooling. Because the hot water system is heated by the VRF system, it is powered by electrical energy from Co|Lab’s photovoltaic solar array. The flooring will be maintained above the outside air dewpoint to prevent floor condensation.
The third element of our MEP approach is Big Ass Fans installed in the 22-foot high bay spaces, which ensure maximum air circulation.
The intelligent building automation system (BAS) will leverage submetered data by process for extensive consumption data. The data will be displayed on a touch-screen dashboard in the building’s lobby. The dashboard will be powered by Schneider Electric and compliant with BACnet protocols. The system of intelligent thermostats will learn occupancy patterns and adapt the schedules to optimize energy efficiency by building section. The tracking system operates on a granular level to ensure proper efficiency goals are met.
The BAS will help Co|Lab achieve our sustainability goals by providing data for better metrics. According to Schneider Electric, consolidating system management into one integrated building management automation system (IBMS) is key to the future of building management. Co|Lab seeks to set the standard for more environmentally-friendly building operations, while testing and reflecting on technology applications.