I am renovating a top-floor apartment (gutted it entirely & rebuilding everything). With new windows and doors, spray foam insulation etc, the space is becoming quite air-tight.

I will be putting exhaust vents in both bathrooms and the kitchen, as well as a multi-split AC system. Heat is electric baseboards & some heated floors (running ducts would be impractical at best in my situation).

How should I set up the air intake? I'm looking into a ERV (or HRV) system install. I have full access to the roof (can add vents etc).

  • You only need a limited amount of make up air two large and you kill the efficiency you are trying to build . consider 1/4-1/2 the volume of air total of the 2 combined if powered and 1/2 to 3/4 if passive. Since you are converting to mini splits consider using them for heat they are more efficient than baseboard heaters. Some utilities have rebates if your mini splits replace baseboard heat because they are more efficient as long as the brand you get is on the approved list (usually energy star certified).
    – Ed Beal
    Dec 27, 2020 at 20:57
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    Most split ACs have close relatives that are AC and Heatpump and will cost perhaps 1/3 as much as your baseboards to run for heating.
    – Ecnerwal
    Dec 28, 2020 at 3:36
  • Thanks for the heat pump suggestions.. this is in Quebec, our winters get mighty cold and from what I read the heat-pump solution isn't as efficient in these circumstances.
    – btk
    Dec 28, 2020 at 15:39

1 Answer 1


This is a nice ductless HRV. Depending on number of bedrooms maybe just put 1 per bedroom. The other units typically require a lot of ducting and are large boxes.


You should consider backer rod and energy seal around window/doors (same technique as chinking).

  • Interesting. Unfortunately I don't have the option of punching through the outside wall (the municipality is super restrictive about "changing the appearance of a building" -- yes, even to put a vent on the wall).
    – btk
    Dec 28, 2020 at 15:40

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