CH-24-C004 - Decarbonizing Buildings with High-Performance Dedicated Outdoor Air Systems (DOAS)

Commercial buildings generate approximately 16% of all US carbon dioxide (CO2) emissions annually, with approximately 52% of commercial energy used to meet the Heating, Ventilation, and Air Conditioning (HVAC) loads (US EIA 2018). As CO2 emissions continue to grow, programs and policies to curb CO2 emissions by minimizing energy consumption become increasingly vital. The Northwest Energy Efficiency Alliance (NEEA) has been investigating and refining an approach to optimize Dedicated Outdoor Air Systems (DOAS) since 2015. This Very High Efficiency (VHE) DOAS approach has been demonstrated to cut CO2 emissions and reduce whole-building energy use by 48% on average across a variety of small to medium commercial building types (Pratt et al. 2022). It has also been shown to improve indoor air quality and occupant comfort over conventional systems. This paper provides an overview of this optimized DOAS approach as a key strategy to help meet building decarbonization goals, including the following critical elements: •Heat or energy recovery ventilator (H/ERV) with > 82% sensible effectiveness, very low crossflow leakage, and high efficiency fans.•High-performance, electrically heated, inverter-driven heating and cooling equipment (e.g., ENERGY-STAR®-rated or equivalent heatpumps and variable refrigerant flow units).•Key design principles:oDecoupled ventilation from the heating/cooling equipmentoRight-sized heating and cooling equipment for the application The high efficiency H/ERV is the enabling element for the success of this approach. These units have been shown to effectively eliminate supplemental conditioning of outside air in coastal climate zones and significantly reduce conditioning needs in more extreme climates. When a high efficiency H/ERV is decoupled from a high-performance electric heat pump, the ventilation and heating/cooling functions can be controlled separately and performance of each optimized. This configuration also allows for decreased run time and energy consumption of the heating and cooling equipment and the ability to downsize the heating and cooling equipment to minimize first cost. NEEA has collected data on over a dozen field sites as well as performing extensive energy modeling on this DOAS system approach. They are sharing their work with other organizations and government agencies aiming to achieve current and future building decarbonization goals and working to grow the high efficiency H/ERV market with cutting edge ventilation products.