As a Passive House the heating and cooling demand at Pumpkin Ridge Passive House are very low, about 10% that of a conventional home. So one of the challenges is to find mechanical equipment sized small enough to deliver those micro-loads efficiently. We used a Zehnder HRV (heat recovery ventilator) to deliver a continuous supply of fresh air and a variable speed Mitsubishi minisplit heat pump to heat and cool the house. See Jonathan Cohen of Imagine Energy describe the mechanical system design:
The home’s elongated form presented an engineering challenge: how to deliver the fresh air and conditioning throughout the house? Imagine Energy implemented a long duct system that steps down in size as it goes, maintaining air pressure so that conditioned fresh air reaches all corners of the home. The minisplit is integrated into the HRV-to-duct system to provide inline heating or cooling of incoming air before it is distributed through the house via the duct system. See Jonathan describe this fusion of systems:
With the home’s energy consumption driven to very low levels by these mechanical systems and the home’s advanced building envelope, a 9.8 kW rooftop solar array brings the home into net zero energy territory.