Hi all, hoping to get a bit of advice on whether or not my HRV plan is going to work out.

I have a 70s split-level ranch in Vermont, about 1,000 sqft per floor, basement is half finished. Kitchen/dining/living room open space plus two bedrooms on the upstairs floor, and another bedroom, plus an open living room/den in the basement, in addition to storage and mechanical systems and laundry. Original heating was natural-gas forced hot air, with supplies just about everywhere on the perimeter of the upper floor, and returns in the kitchen and living room on either side of the center beam. The ducting was badly hacked at one point to try to add supplies in the basement too, so it’s generally a mess, and the furnace was from the late 80s when they added gas.

Long story short, we now have a minisplit in each bedroom and the main open living area on the upstairs floor, DIY installed. I also spent a bunch of time air sealing the place last fall, and frankly it’s pretty tight for this era/type of house: rim joists are spray foamed, new baseboards are caulked to the walls and pressed tight against the floors, all ceiling fixtures are caulked electrical boxes in walls are sealed up as best I can, windows and doors are new ish, etc. I haven’t done a blower door test so no real numbers here, but a few months ago before I swapped the NG water heater for a HPWH, we had issues with the water heater back-drafting into the house if it fired up with both the microwave vent hood (300CFM) and bathroom exhaust fan (80 CFM) going so it’s pretty tight. We also had surprisingly high RH last winter heating with just minisplits, hovering around 55-60% unless we ran the dehumidifier (which we did, a lot) or cracked a window. Double-pane windows were covered in water anytime it was lower than ~35 outside. We only used about 1500kWh all heating season to heat the place last winter (I have energy metering per breaker).

So between high RH, stale smelling air, and stupid low total energy used to heat last winter, I’m reasonably sure we need mechanical ventilation. I’m hoping to also encourage some air mixing from the upper floor to the basement (especially with the HPWH now cooling the basement; if I do nothing I’m going to have to switch it to resistive mode in the winter because it’s already ~45-50 in the basement with no heating). I may add a minisplit in the basement at some point; right now there’s resistive baseboard that stays unused unless we’re actually down there, which is a rare occasion besides doing laundry or other short tasks.

My tentative plan is to keep the bathroom exhaust fan as-is, and put an HRV in the basement with fresh air distributed to the bedrooms and the living room using some of the original supply ducting, and stale air drawn from the basement (coincidentally, where we keep the cat litter boxes seems like a good choice 🙂 ).

So my questions are:

1. How doable is countering the stack effect with an HRV, with fresh air distributed on the upper floor and stale air pulled from the lower floor?
2. Am I going to have issues balancing an HRV with my 400CFM kitchen vent hood, 80CFM bathroom exhaust, and a dryer? As an alternative plan, I could easily re-use the floor supply register in the bathroom as my stale air return to the HRV, but this wouldn’t accomplish the mixing effect I’m hoping to get with some warm upper-floor air moving into the basement.
3. Any other issues with my plan I haven’t considered, or alternative HRV layouts I should consider in a raised ranch with minisplit heating?