ERV
≈ 75% sensible
Typical recovery
Also transfers moisture between streams
ERV vs HRV
Both bring outdoor air in and stale air out through a core that recovers most of the heat. The only difference is whether the core also moves moisture — and in most of the country that single difference settles the choice.
Updated 2026-09-04
Our pick — an ERV in humid summers or very dry winters; an HRV in a cold, damp climate with a wet basement
HRV
≈ 80% sensible
Typical recovery
Heat only; moisture goes out with the exhaust
What each core does
A heat recovery ventilator passes incoming and outgoing air through a core that lets heat cross between the streams but not moisture. In winter the outgoing warm air preheats the incoming cold air; the humidity in the exhaust leaves the building.
An energy recovery ventilator uses a moisture-permeable core, so a share of the water vapour crosses too. In summer that keeps humid outdoor air from dumping its moisture load indoors. In winter it keeps some indoor humidity from being thrown away.
The comparison
| Factor | ERV | HRV |
|---|---|---|
| Transfers heat | Yes | Yes |
| Transfers moisture | Yes, partially | No |
| Humid summer | Reduces the latent load coming in | Brings the moisture straight in |
| Very cold, dry winter | Retains indoor humidity | Dries the house further |
| Damp basement or high indoor moisture | Keeps some of it indoors | Better — exhausts it |
| Core condensation and frost | Less frost risk | Needs a defrost strategy and a drain |
| Maintenance | Core cleaning, filters | Core cleaning, filters, condensate drain |
| Cost | Slightly higher | Slightly lower |
Choosing by climate
Humid summers dominate the decision in most of the United States: if you spend the cooling season fighting latent load, an ERV keeps some of that load outside where it belongs. In a very cold, very dry winter climate the same core helps in the opposite direction, by not throwing away the humidity you generate.
An HRV earns its place where indoor moisture is the problem rather than outdoor moisture: a cool damp climate, a house with a wet basement, or a tight house with a lot of occupants and cooking. There, exhausting moisture is the feature.
Neither is a dehumidifier
An ERV reduces the moisture a ventilation system brings in. It does not remove moisture the house already has. If indoor humidity is high with the ventilator off, the answer is a dehumidifier or a properly sized air conditioner running long cycles — not a different core.
Sizing and installation
Ventilation airflow is a function of floor area and occupancy, and it is set by the residential ventilation standard your jurisdiction adopts — check which one before sizing. Once you have the CFM, the duct is sized like any other duct; the duct size calculator works the same way at these small airflows.
Two installation notes that decide whether the unit is any good in practice. Balance the two airflows — an unbalanced unit pressurises or depressurises the house, which is exactly what you were trying to avoid. And filter the incoming stream properly: the unit's own screens are coarse, and EPA's guidance for a system filter is MERV 13 or as high as the equipment allows.
Sources: US EPA, Indoor Air Quality — What is a MERV rating? (read 2026-09-04)
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