Is a ducted HPWH a good idea?
I am planning to build a house in zone 5A. It is to be a high performance home with levels of insulation and air leakage approaching Passive House standard. My builder likes to install a heat pump hot water heater with inlet and exhaust ducting to the outside. The HPWH would be installed in a conditioned basement. Is this a good idea? Is there a “cold weather” HPWH suitable to this application?
This article describes a test of ducted vs unducted HPWH:
The ducted HPWH reduced home thermal load by 7.8% (5.7 kWh/day), while increasing HPWH electrical load by 4.8% (0.44 kWh/day). So a possibly significant savings. The problem is that the ducted HPWH was referenced to a crawl space that maintained 44±2°F during the heating season, and the temperature of the closet containing the ductless HPWH was depressed to 56° from overall indoor temperature of 71°. The result implies that the COP of the HPWH was nearly the same at 44 and 56°. The conditions are perhaps not so relevant to my situation.
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