Energy recovery ventilation (ERV) brings in fresh outdoor air while capturing the energy in the air being thrown out. At its heart sits an air-to-air heat exchanger. Without it, mechanically ventilated buildings waste most of the energy spent conditioning air.
ERV vs HRV
The terms are often used interchangeably, but there is a difference:
- HRV (heat recovery ventilation): transfers sensible heat only.
- ERV (energy recovery ventilation): transfers both sensible heat and moisture (total enthalpy).
In humid summers or dry winters, ERV also balances indoor humidity, reducing both cooling load and comfort complaints. A rotary wheel naturally does enthalpy recovery; a plate unit needs a desiccant-coated or membrane core for moisture transfer.
Where the savings come from
With 100% outdoor air, heating and cooling loads scale with ventilation rate. An ERV returning 70%–80% of that energy cuts the associated HVAC energy by a comparable fraction. In cold climates the payback is often under two years; in mild climates it is longer but still positive over the equipment life.
Climate guidance
| Climate | Recommendation |
|---|---|
| Cold winter | HRV or ERV with frost protection (wheel or plate by-pass) |
| Hot & humid | ERV to limit moisture load |
| Hot & dry | ERV to retain indoor humidity |
| Mild | HRV is usually enough |
Sizing basics
Match the ERV to the design ventilation airflow (m³/h or CFM), not to peak HVAC capacity. Balanced supply/exhaust maximizes recovery; large imbalances waste effectiveness. Frost control matters when exhaust can drop below freezing—use preheat, by-pass or a wheel. See our sizing guide for the calculation steps.
Designing an ERV for a new or retrofit building?
EN159 supplies plate and rotary air-to-air cores for ERV/HRV units, including frost-protected and enthalpy configurations.
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