I am having trouble deciding on the right solution for a ventilation retrofit in my 1980 tow home in the pacific northwest (temperate rainy winter, hot dry summer, wildfire smoke seasonally). Doors and windows are new so, so the place is sealed up. The place has no crawlspace or basement. The ideas I have are to put a ducted erv/hrv in or ductless hrv/erv.
For ducted, the only space is in the unconditioned attic for both the unit and the ventilation ducting. Air supply to rooms from ceiling vents and then air exhaust from a vent downstairs and two vents upstairs. I cant find a good way to get air intake from side wall of exterior. Instead it would be from asphalt roof vent, which doesnt seem great.
For ductless, it seems much simpler but i wonder about actually getting good air filtration. And then we have four upstairs rooms and we need at least one downstairs too, i think. Seems like filters are, like $100??
Any ideas or advice would be much appreciated.