When the windows stay closed and the heating system runs every day, many homeowners wonder whether an air exchanger should keep running or be shut off to save heat. In most homes equipped with a properly installed heat recovery ventilator or energy recovery ventilator, winter is exactly when controlled ventilation matters—but the correct setting is not always “high.”
The short answer
Usually, an HRV or ERV should continue operating during winter according to its designed controls. Natural Resources Canada guidance commonly recommends low-speed continuous operation, especially in airtight homes, with higher ventilation when moisture, odours or occupancy increase.
The best setting depends on the home, the installed equipment and indoor humidity. An HRV can reduce excess winter moisture, but too much ventilation can also make an already-dry house feel drier. Rather than turning the system off or leaving it on maximum, monitor conditions and follow the owner’s manual and the settings established when the system was balanced.
What an HRV or ERV does
Both systems exhaust stale indoor air and bring in outdoor air through separate air streams. During the heating season, heat from the outgoing air is transferred to the incoming air, reducing the heat lost compared with simply opening windows.
- HRV: transfers heat and usually removes more indoor moisture during cold weather.
- ERV: transfers heat and some moisture, which can help retain humidity in a home that becomes very dry.
Neither system creates heat or replaces the furnace, heat pump or boiler. It also does not replace smoke and carbon-monoxide alarms or correct a problem with a fuel-burning appliance.
What the common settings mean
Controls vary, so the labels on your wall control may not match these exactly.
- Low or continuous: provides steady background ventilation and is often the normal winter setting.
- Intermittent: alternates between ventilation and standby. It may be appropriate where the installation and household load permit it.
- Boost or high: increases ventilation temporarily during showers, cooking, gatherings or periods of high humidity.
- Recirculate: moves indoor air without necessarily bringing in outdoor air. It should not be mistaken for fresh-air ventilation.
- Humidity control: may increase ventilation when indoor humidity rises above the selected level. It is a ventilation control, not a humidifier.
Signs you may need more ventilation
- Persistent condensation or frost on windows
- Lingering cooking, pet or household odours
- A stuffy feeling that returns quickly
- High indoor humidity or recurring dampness
- Visible mould or a musty odour
Health Canada identifies condensation, mould, lingering odours and stuffiness as signs that ventilation may be too low. Increase only through the normal homeowner controls described in the manual. If the symptoms continue, have the ventilation system checked rather than changing dampers or fan wiring.
Signs ventilation may be too high
- Very dry indoor air despite a reasonable humidity-control setting
- Persistent drafts or discomfort near supply grilles
- Unusually high heating use without another clear explanation
Health Canada lists very dry air, drafts and higher-than-average heating or cooling bills as possible signs of excessive ventilation. Measure with a hygrometer before changing settings. Our winter humidity guide explains why a reading is more useful than judging by static or dry skin alone.
Safe checks a homeowner can make
- Read the wall-control and HRV or ERV manual so you know what each mode actually does.
- Record indoor humidity at the same time each day and note whether condensation appears as outdoor temperatures fall.
- Confirm that a bathroom or kitchen boost control increases ventilation when used.
- From ground level, check that outdoor intake and exhaust hoods are not blocked by leaves, snow or frost. Do not use a ladder or insert tools into the openings.
- Clean or replace accessible filters only if the owner’s manual identifies this as routine homeowner maintenance. Disconnect power exactly as the manual directs and never open wiring or control compartments.
- Keep indoor supply and exhaust grilles free of furniture, dust buildup and stored items.
If wet windows are the main concern, our window-condensation guide covers other moisture sources that ventilation alone may not solve.
When to arrange professional service
Have the system assessed if airflow is absent or unusually weak, frost keeps returning inside the unit, water is leaking, the unit makes a new grinding or rattling noise, controls do not respond, or the home remains very damp or very dry despite reasonable settings.
The supply and exhaust airflow must be balanced for the home. Do not adjust balancing dampers, fan speeds, wiring or electrical components yourself. Natural Resources Canada recommends that HRVs and ERVs be installed, balanced and commissioned by a qualified technician.
For homes around Schomberg, the first sustained cold weather is a useful time to compare indoor humidity, window condensation and ventilation settings. Record those observations before calling; they help a technician understand how the system behaves as outdoor conditions change.
For help with an HRV, ERV or heating-system airflow, review our heating service options and call Schomberg Heating & Cooling at (905) 939-2350. For time-sensitive service, call rather than relying on the website form.