Blog · Kitchener
HRV maintenance in newer Kitchener homes: filters, core, drain and the outside hoods
If your house in Doon South, Huron Park or north Waterloo was built in the last couple of decades, there is probably a heat recovery ventilator in the basement next to the furnace. It is easy to forget, and it needs more attention than most owners give it.
Last updated September 25, 2026 · Reviewed by the Kitchener Duct Cleaning team
What the HRV does
A heat recovery ventilator exchanges stale indoor air for fresh outdoor air. Canada Mortgage and Housing Corporation explains that HRVs and ERVs transfer heat between the outgoing and incoming airstreams without mixing them, so the fresh air coming in is warmed by the air going out. An HRV uses a core of metal or plastic plates that transfers heat. An ERV uses a core that transfers both heat and moisture, which helps with humidity control.
Newer, tighter houses need this mechanical ventilation because they do not leak much air on their own. When the HRV is off or clogged, the result is usually stuffy rooms, lingering cooking smells and heavy condensation on windows in January.
A maintenance schedule you can follow
Natural Resources Canada and CMHC both publish HRV maintenance guidance. Put together, a workable schedule for a house looks like this:
- Every 1 to 3 months: filters. NRCan recommends cleaning or replacing the HRV's air filters every one to three months. Washable filters can be vacuumed, then washed in mild soap and water, and they last several years.
- Every 3 months: outside hoods. CMHC lists cleaning the exterior intake hood and screen every three months. NRCan says to check hoods for grass, leaves and other debris, and more often in fall and winter when leaves and snow and frost build up.
- Twice a year: the core. NRCan recommends inspecting and cleaning the heat-exchange core twice a year. Follow the manufacturer's instructions for removing and washing it.
- Twice a year: the condensate drain. NRCan suggests pouring two or three litres of warm water into the drain pan to confirm it flows freely, and notes the drain line needs a trap.
- Every 6 to 12 months: fans, drain pan and grilles. CMHC lists cleaning fan blades and the drain pan every six months and grilles and diffusers every year.
- Yearly: balance. NRCan recommends having a qualified contractor check that the supply and exhaust airflows are balanced.
Always turn the unit off and unplug it before opening the door.
Checking the balance yourself
NRCan describes a simple check that homeowners can do between professional visits: hold an empty plastic garbage bag over the outside intake hood and time how long it takes to inflate, then do the same over the exhaust hood and time how long it takes to deflate. In a balanced system the two times should be about the same, within a matter of seconds. A big difference suggests a blocked filter or hood, a damper out of position or a disconnected duct, and is worth having a contractor look at.
Winter in Waterloo Region
NRCan notes that most HRVs start an automatic defrost cycle when it drops below about minus 5 degrees Celsius, which is routine here for much of the winter. It also recommends adjusting the dehumidistat through the season: enough ventilation to keep condensation off the windows, but not so much that the house becomes uncomfortably dry. If the house is very dry, running the HRV at a lower setting or intermittently can help, and an ERV is an option when the unit is eventually replaced.
Snow drifts and frost can block the outside hoods on the side of a house, particularly on the narrow side yards common in newer subdivisions. A blocked intake starves the house of fresh air; a blocked exhaust can unbalance the system.
Signs something is wrong
- Heavy window condensation even with the HRV running.
- Water on the floor under the unit, usually a plugged drain or missing trap.
- A musty smell from the unit or the fresh-air supply.
- Noise from the fans, or a unit that has been switched off because someone found it noisy or thought it was wasting heat. CMHC notes that occupants turning systems off leads to a buildup of pollutants and humidity.
- Filters that come out grey and matted at every check, which may mean the hood screen is torn or missing.
How the HRV relates to your furnace ducts
In many houses the HRV is connected to the furnace's return duct, so fresh air is distributed through the furnace ductwork, while stale air is pulled from bathrooms and the kitchen area through the HRV's own small ducts. In others the HRV has its own fully separate duct system. Knowing which one you have tells you what a duct cleaning covers.
In a new build, both systems can collect drywall dust and construction debris before anyone moves in. If you are booking a new-home duct clean-out or whole-home duct cleaning, tell the crew there is an HRV and ask whether its ducts and core are included in the written quote, so there are no surprises. Planning ranges are on the Kitchener duct cleaning cost guide. The crew works across Kitchener, Waterloo and Breslau; start with the contact page.