[organsnyder]

That's what we did. Our house was built in 1916, but the weather sealing we've done combined with six people breathing in it led to quite high CO2 levels. We have a traditional ducted air conditioning system in the attic (heat is hot water radiant), and added the ERV there. It made a massive difference.

[ericd]

Yeah, same here on most counts, even going down to 3 ACH on the blower door test made CO2 levels pretty high, now they’re barely above outdoor.