Before I commit the time (and money) I thought reaching out for tips may be worthwhile. I have a 1935 built 1800sq ft, 2 story home with an instant hot water heater combi boiler (baseboard hot water heat 2 zones, 1 for each floor) and a newly installed 24k btu minisplit on the second floor next to the stairs. Humidity in the house is usually comfortable (for me) at 40-60%, basement humidity is controlled with dehumidifier to keep @ or below 65%.
In summer with single point for A/C temperature varies 3-4 degrees between floors (and some room to room upstairs). In winter, baseboards upstairs are rarely working while downstairs is on seemingly non stop. Air quality can at time seem stuffy, especially in the winter time when windows are closed up.
After looking at more expensive HRV and ERV systems I think I have settled on just an air mixing solution, I know they are not as energy effecient (one of my concerns). After being inspired by this: Fantech-AEV1000. I made the leap that I could just split the intake/outtake from this Air King QFAM 6in 120 CFM and produce effectivley the same thing. I'm looking for the best way to even the temperature throughout the house (an minimize the amount of ductwork needed to run so I thought of having one channel run to the floor of the first floor and the other run to the ceiling of the second. The ventilation plans would then be, exhust from the second floor and supply air to the first floor in the summer (to pull more of the AC into the rooms of the second floor) and reverse in the winter (either by flipping the unit or giving enough slack in the ducts to move them), each floor would get 4 vents ea. at a close to even distribution.
(1)Am I going to kill my energy bills with just an air mixer vs the HRV? (2)Even though I only have a 2 story home will the vent locations proposed help to balance the temps by playing off the stack effect? (3) Ductwork going to the second floor will need to run through the attic, I hope to get by with using insulated flexible ducts in these locations, any concerns by using this?
I am aware that older homes typically don't need ventilations systems (due to leaky construction) but with the air sealing I have done and upgrading of insulation that may be mitigated. In addition I would much prefer to know that my air is coming in through a known point (and filtered being near a main road) as well as getting a better distribution of temps. I am open to any suggestions that could achieve these goals (so long as they don't blow open my budget) and would love to hear thoughts on my plan and concerns, thank you all in advance!