Missing or dirty air exchanger (échangeur d’air): what it is, how serious, what it costs

An air exchanger, « échangeur d’air » in a French report, renews the air in the house. It draws out stale, humid air, often from the bathrooms, and sends it outside. At the same time, it brings in fresh air and warms it with the heat of the air going out. It is also called an HRV, for heat recovery ventilator, or an ERV when it also recovers part of the humidity.

Recent houses, built very airtight, almost all have one. Older, leakier houses often do not. Reports say “no air exchanger”, “dirty filters” or “air exchanger not inspected”.

Rarely serious. In analyses, I usually put it under “Can wait”: a filter to clean is maintenance, and adding an air exchanger to an older house is a comfort upgrade.

It matters more when the report also notes condensation on the windows in winter, mould or high humidity: the air is not being renewed enough. And in a recent, very airtight house, an air exchanger that is off or poorly connected deserves a check.

Replacing the air exchanger filters: $100 to $300. Repairing an air exchanger that does not work: $250 to $800. Having a ventilation specialist evaluate the system: $400 to $600. Installing an air exchanger for the whole house: $3,000 to $6,000.

These are ballpark figures for Quebec, to be confirmed with quotes.

1. Was the air exchanger running, and what shape were the filters in?
2. Did you see signs of moisture: condensation on windows, mould, a stale smell?
3. Are the ducts insulated where they run through the attic, and are the outside hoods clear?

Ask the seller when the air exchanger was last serviced.

Does your report mention the air exchanger? Upload it: in five minutes, I tell you what comes first, what to have checked and what to ask the seller.

Clean the filters and check the outside hoods a few times a year, following the manufacturer’s instructions. A fuller service by a technician from time to time keeps it efficient.

No. A heat pump heats and cools. An air exchanger does not heat: it renews the air in the house.