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CO2 Heat Pump Water Heater in Madrona Passive House

Seattle’s residential building code requires domestic hot water heating system be tested and listed by a testing agency approved by the State of Washington. in the 1990s, Japanese engineers developed heat pump domestic hot water heaters using CO2, an abundant, natural refrigerant. These systems are known as “Eco-Cute” which means environmentally-friendly hot water because using CO2 avoids conventional synthetic refrigerants which have high global warming potential (GWP). Although Sanden’s Eco-Cute is not yet tested by an approved agency, the City of Seattle’s Innovative Technology Advisory Committee (ITAC) recommends Hammer & Hand be permitted to install the CO2 system as an alternate material because of its superior performance and environmental attributes if it meets four conditions.