HRV: connect to the air handler or not?
We are planning to put an HRV in our new home. My HVAC contractor is proposing that we connect the HRV fresh air supply to the return on the air handler. I have read here on GBA and elsewhere that HRVs work best when they have their own dedicated exhaust and supply ducts. His plan would call for programming the thermostat to run the AH periodically to distribute the fresh air. Please advise me, whether this plan would be a good one for our home (see below), or whether we should spend extra to have supply ducts run from the HRV.
We are building a pretty good, 1,590 sq ft house in climate zone 4c (western Oregon). We are using a conditoned crawl (R21), 2×6 walls with R5 foam, and stuffing as much insulation in the attic as possible (average R50). We are also carefully air sealing. The goal is to get to 2-3 ACH with the blower door.
The floorplan is open–basically two bedroom separated by a large kitchen great room. There will be a wood stove with outside combustion air that we will use daily from November through March. The forced air heat pump will be mostly supplemental, but that may change as we get older and lazier about cutting wood.
The crawl requires 32 cfm by code and this will be supplied by the HRV with a supply and exhaust duct. There will also be HRV exhaust ducts in each of the two baths. The living space will get somewhere between 30-60 cfm of fresh air, depending on whose standard you use. I am concerned that the HRV will be operating continuously, but the AH won’t (don’t want it to), and that the fresh air will not be well distributed in the AH ducting when the AH is off.
Are we better off to spend the extra $’s to put HRV supplies in a couple of places now? I am thinking the great room and master bedroom. Ideas? Thanks!
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