Addition ERV and Heat Pump choices
We’re putting an addition on our 1920s house in CZ5 (but close to CZ4). The addition will be two stories, each about 550 sq ft. Upstairs will be primary suite (bedroom / bath / walk in closet) and downstairs will be generally open living space, but also include a mudroom and bath. The addition will have its own HVAC due to the difficulty of running ductwork to the new section.
The HVAC contractor was OK with a 1.5 (to 2) ton heat pump for the new addition and the plans have ducted system. Despite the old part of the house being relatively leaky by modern standards, I’m looking at an ERV that would primarily service the addition. The ERV could be generally tied into the new heat pump ductwork.
The other option I was considering would be to change to a 2 head mini-split system (one head per floor). The ERV would then have a separate cheap duct system to help move air from the large rooms to the small rooms (bathroom/closet…). The mini-splits would seem to generally have some efficiency gains compared to a ducted system and save on some ductwork costs.
Does the latter seem like an improvement or am I better off with a traditional setup? Thanks.
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Replies
You definitely want the ducted unit with the ERV. The smallest wall mount is 2x to 3x oversized for even a very large bedroom, the multizone will be hard to get right. Plus with a ducted unit you can have real air filters.
A quick check of heat loss in one of the on-line calculators (coolcalc or BetterbuiltNW hvac calculator) might be in order, 2 tons sounds too big unless you have a wall of glass.
Shared ERV ducting can work with modulating heat pumps that run the blowers most of the time anyways. I would look at getting an autobalance ERV unit (Panasonic IB100 or Broan AI) as these are not effected by the pressure changes in the ducts and are much easier to balance.