Quick answer: A heat recovery ventilator (HRV) is not a dehumidifier. It replaces indoor air with outdoor air and recovers heat between the two streams. It lowers indoor humidity only when the outdoor air holds less water than indoor air, which is usually true in cold winters and false in humid summers. An energy recovery ventilator (ERV) also transfers some moisture between the streams, which keeps indoor air from drying out in winter and reduces the moisture brought in by summer ventilation, but it still does not remove the moisture generated indoors. Where indoor moisture is high or outdoor air is humid, add a dehumidifier.
Quick answer
- HRV: dries the building only when outdoor air is drier (water content, not RH).
- ERV: transfers part of the moisture between streams; reduces summer moisture intake.
- Neither removes indoor moisture sources the way a dehumidifier does.
Compare water content, not RH
| Indoor | Outdoor | HRV ventilation effect |
|---|---|---|
| 21 °C, 55 % RH (8.5 g/kg) | 0 °C, 85 % RH (3.2 g/kg) | Lowers humidity |
| 21 °C, 55 % RH (8.5 g/kg) | 20 °C, 70 % RH (10.2 g/kg) | Raises humidity |
| 24 °C, 50 % RH (9.3 g/kg) | 30 °C, 70 % RH (18.8 g/kg) | Raises humidity strongly |
HRV vs ERV
| HRV | ERV | |
|---|---|---|
| Transfers | Heat (sensible) | Heat and some moisture |
| Winter | Lowers indoor humidity (can over-dry) | Retains some indoor moisture |
| Summer (humid) | Brings outdoor moisture in | Brings in less moisture than an HRV, but still some |
| Indoor moisture sources | Removed only by exchange with drier air | Same |
US DOE research has worked on ERV cores with high moisture transfer to improve humidity performance in ventilation (US DOE).
When an HRV/ERV is enough
- Cold or dry climates in the heating season.
- Buildings with modest indoor moisture (offices, homes) and good air-tightness.
When to add dehumidification
- Humid summers or tropical climates.
- High indoor moisture: pools, kitchens, laundries, crowded spaces, wet processes, greenhouses.
- Basements and below-grade spaces.
- Buildings where humidity must stay below a limit for goods or equipment.
In commercial buildings, a common arrangement is ventilation with energy recovery for fresh air, plus a dedicated dehumidifier controlled on humidity. See can you run an AC and dehumidifier at the same time, how air conditioning controls humidity, and our ceiling-mounted and ducted dehumidifiers.
FAQ
Frequently asked questions
Does an HRV reduce humidity?
Only when outdoor air holds less water than indoor air, typically in cold weather.
Is an ERV better for humid climates?
It brings in less outdoor moisture than an HRV, but it does not dehumidify; humid climates usually still need dehumidification.
Can an HRV replace a dehumidifier?
In cold, dry seasons it may keep humidity in range; in humid weather or with high indoor moisture, no.
Sources
- US DOE, Low-cost energy recovery ventilator core with high-flux moisture transfer.
- ASHRAE Handbook—HVAC Systems and Equipment, Air-to-air energy recovery equipment.
