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HRV vs ERV for an Ontario House: Which One, and Why Your New House Needs One at All
Heating and efficiency Ventilation From a builder
HRV vs ERV for an Ontario House: Which One, and Why Your New House Needs One at All
A new house built to today’s Code is tight enough that it cannot breathe on its own, which is the point. The HRV or ERV is the lungs. Here is what each one does, which one I put in and why, and how to tell if yours is actually working.
Short version: Both bring fresh outdoor air in and push stale air out through a core that recovers heat from the outgoing air. An HRV recovers heat only; an ERV recovers heat and some moisture. In a tight Ontario house with a normal family, an ERV helps keep winter humidity up and summer humidity down; an HRV is the choice where indoor humidity runs high (lots of people, a pool, a damp site) because it dries the house out. Either one only works if it is sized to the house, ducted to the bedrooms, balanced after installation, and left running. The Code requires the ventilation; the balancing report proves it.
Why the house needs it
An ICF house, or any house built to the current Code with a sealed vapour barrier and good windows, leaks very little air. That is what makes it cheap to heat. It also means the moisture from cooking, showers and breathing, and the carbon dioxide and off-gassing from furniture and finishes, stay inside unless something moves them out. The Ontario Building Code requires a principal ventilation system in every new house, and the SB-12 energy packages set a minimum heat recovery efficiency for it. In practice that is an HRV or an ERV. Air sealing an Ontario home explains why tight and ventilated beats leaky every time.
How they work, and the one difference
Both units have two fans and a core. Stale air from bathrooms, the kitchen area and the laundry is pulled through one side of the core and exhausted outside; fresh air from outside is pulled through the other side and delivered to the bedrooms and living areas. In the core the two streams pass each other without mixing, and the outgoing warm air gives up most of its heat to the incoming cold air. A good unit recovers 65 to 85 percent of the heat.
The HRV core transfers heat only. The ERV core also lets water vapour cross, so in winter some of the moisture in the outgoing air goes back into the incoming dry air, and in summer some of the humidity in the incoming air is passed to the outgoing stream before it enters the house.
Which one for an Ontario house
| Situation | Pick | Why |
|---|---|---|
| Typical family in a tight new house | ERV | Winter indoor air in a tight house gets very dry with an HRV; the ERV keeps humidity in a comfortable range and helps in humid summers |
| High indoor moisture: many occupants, indoor pool, hot tub, damp basement, lots of plants | HRV | You want the moisture out; the HRV dries the house |
| Very cold region, long winter | Either, with a defrost strategy | Both need defrost below about minus 10; check the unit is rated for your winter |
| Air conditioning in a humid summer | ERV | Reduces the moisture load the air conditioner has to remove |
| Older leaky house being renovated | HRV is fine | The house leaks enough that over-drying is not the problem |
For the ICF houses we build in Simcoe County, with radiant floors and no forced-air humidity swings, the ERV has been the better unit for most families. A house with a pool gets an HRV. NRCan’s Keeping the Heat In has a plain chapter on ventilation if you want the long version.
Sizing, ducting and balancing
- Size from the Code’s ventilation rate for the number of bedrooms and the house, or from the mechanical design; the HVAC designer does this as part of the F280 package. Building Code HVAC requirements lists the rates.
- Duct it properly: exhaust from every bathroom, the kitchen area (not the range hood) and the laundry; supply to each bedroom and the main living space. A unit that just dumps into the furnace return ventilates the furnace.
- Insulated ducts to the outside, with the intake and exhaust hoods well apart and away from dryer vents, gas vents and the driveway.
- Balance it after installation: the installer measures the supply and exhaust flows and adjusts them to match. The balancing report is what the inspector asks for at final, and it is the only proof the thing works.
- A control the family will use: a main-floor controller with a boost button in the bathrooms. Units on a crawl space wall with no control get switched off in October and never turned on again.
The mistakes
- Switched off to save electricity. The fans cost pennies; the mould costs a renovation.
- Filters never cleaned; the core clogs and the unit moves no air. Clean every three months, check the core yearly.
- Intake hood near the dryer vent or the barbecue.
- Exhaust ducted into the attic. Still happens.
- No defrost cycle in a cold region; the core freezes solid in January.
- Never balanced; one bedroom gets all the fresh air and the rest get none.
Related guides on this site
Sources and further reading
Questions people ask
Do I need an HRV in a new house in Ontario?
Yes. The Ontario Building Code requires a principal mechanical ventilation system in new houses, and the SB-12 energy packages set a minimum heat recovery efficiency, which in practice means an HRV or ERV.
What is the difference between an HRV and an ERV?
Both recover heat from outgoing stale air to warm incoming fresh air. An ERV also transfers some moisture, keeping winter indoor air from getting too dry and reducing summer humidity. An HRV transfers heat only and dries the house.
Which is better for a cold climate, HRV or ERV?
For a typical family in a tight house, an ERV, because winter indoor air gets very dry otherwise. For a house with high indoor moisture (pool, many occupants, damp site), an HRV. Both need a defrost strategy for Ontario winters.
Why is my HRV not working?
Usually it is switched off, the filters or core are clogged, it was never balanced, or the ducts were not run to the rooms that need them. Check the balancing report and the filters first.
Size it from a heat loss, not a guess
Every heating choice starts with the heat loss of your actual house. OntarioHeatLoss.ca produces the CSA F280 calculation and the mechanical design your permit needs, anywhere in Ontario.
Reviewed and updated October 2026. Costs are Ontario ranges, not quotes; code references are to the Ontario Building Code in force at that date.
