Every new Ontario home needs mechanical ventilation, and the choice comes down to two boxes that look identical on the wall: the HRV (heat recovery ventilator) and the ERV (energy recovery ventilator). Both bring in fresh air and exhaust stale air while recovering heat from the outgoing stream. The difference is one thing: an ERV also transfers moisture; an HRV does not. In Ontario’s climate, that one difference decides winter humidity, window condensation, and how dry your house feels in February.
This guide gives you the honest answer — including why the traditional “always HRV in Ontario” advice is changing for tight new builds — and what OBC 2024’s mandatory MVDS requires you to document either way. For the design service, see HRV/ERV ventilation design.
Recovers heat from outgoing air; moisture is exhausted with the stale air. Net effect: it dries the house in winter. Right choice when the home runs humid — busy kitchens, lots of showers, older or leakier envelopes, indoor pools nearby, or any house fighting window condensation.
Recovers heat and transfers some moisture between airstreams — keeping winter humidity in and summer humidity out. Right choice for tight, well-insulated new builds that get uncomfortably dry at -20°C, and for air-conditioned homes where summer humidity load matters.
Not the brand brochure — your envelope tightness, occupancy, and how the house runs in January. A tight new build with two occupants trends dry → ERV. A family of six with a leakier envelope trends humid → HRV. This is a design decision, and it belongs in the MVDS with the sizing math behind it.
For decades the default advice here was “cold climate = HRV.” That’s still right for many homes — but OBC 2024-era new builds are much tighter than what that rule was written for, and tight houses in deep winter trend dry, not damp. That’s why ERVs keep showing up in new Ontario construction. The point isn’t that one box wins; it’s that the choice should come from your house’s numbers, not a habit.
Winter is exactly when your sealed house needs it most — that’s when windows stay shut and indoor air quality is worst. If running it makes the house too dry, that’s a balancing or selection issue to fix, not a reason to shut off your fresh air.
Exhaust-only fans throw air out without recovering heat and without controlled fresh-air supply. The OBC’s ventilation requirements for new homes are about balanced, designed ventilation — which is why the MVDS exists.
Sizing (CFM per the occupancy and bedroom count), duct layout, and whether the unit is fully ducted or simplified-connected to the furnace all change performance — and all have to be documented for the permit. The box is maybe a third of the outcome.
New homes require mechanical ventilation meeting the OBC’s requirements, and since January 1, 2025 the permit package must include the Mechanical Ventilation Design Summary documenting it. In practice that means an HRV or ERV in nearly every new Ontario home. What’s mandatory is the documented, code-compliant system — not one specific box.
An HRV — it exhausts indoor moisture without returning any, actively drying the house. Persistent winter condensation is one of the clearest signals the house wants an HRV (or that an existing system needs rebalancing).
Comparable units are close in price, with ERVs typically somewhat more for the enthalpy core. Operating cost differences are small next to the comfort difference — which is why the selection should follow the house, not the price tag.
Simplified and extended connections to the forced-air system are common and can comply when designed correctly — interlock with the furnace fan, correct connection points, and documented airflow. Fully dedicated ducting performs best. Either way, the configuration has to be shown in the permit documents.
Formally, the designer who signs your ventilation design. We make the call from your envelope specs, occupancy and climate zone, size the unit, lay out the ducting, and deliver the BCIN-stamped MVDS your municipality requires — in 48 hours.
Building or renovating? The HRV/ERV decision, sizing, and the mandatory MVDS — done right, stamped, in 48 hours.
Get Free Quote →Upload your floor plans and tell us your municipality. We select HRV or ERV from your home’s actual characteristics, size it to code, design the duct connection, and deliver the MVDS and Schedule 1 your building department requires — every page BCIN-stamped.