Air
Heat Recovery Ventilator
HRV
Also known as heat recovery ventilation
A balanced ventilation system that exhausts indoor air and supplies outdoor air through a core that transfers heat between the two streams without meaningfully transferring moisture between them.
In more detail
An HRV and an ERV are the same machine with different cores. Both run supply and exhaust streams past each other, and both recover most of the heat. The difference is water vapor: an HRV core is essentially vapor-impermeable, so moisture in the outgoing stream leaves with it, while an ERV enthalpy core passes a portion of it back.
That single difference decides which one suits a house. In a cold, dry winter climate, an HRV exhausting humid indoor air and bringing in dry outdoor air can pull a house uncomfortably dry, and an ERV moderates that. In a hot, humid summer climate, an HRV delivers the full moisture load of outdoor air into the house for the cooling system to remove, while an ERV sheds some of it before it arrives. Where interior moisture is a surplus rather than a scarcity — a tight house with high occupancy, indoor drying, or an indoor pool — the HRV willingness to export humidity is the feature rather than the flaw.
Neither device is a humidity control system. Both moderate the moisture that arrives with ventilation air. Actual control, in either direction, needs dedicated equipment.
Why it matters
The HRV-or-ERV question comes up on every airtight house and gets answered badly more often than almost any other mechanical decision, usually by defaulting to whatever the installer stocks. The consequence is a winter at 20 percent indoor humidity, or a summer with a cooling system fighting ventilation air it was not sized for. The right answer depends on climate and on how much moisture the household actually generates, and it is far cheaper to get right at specification than at replacement.
The common misunderstanding
That an HRV is simply the cheaper or lesser version of an ERV. They are different tools. An HRV exports indoor humidity, which is a liability in a dry winter and an asset in a house that generates more moisture than it can shed. Climate and occupancy decide between them, not price.
Related terms
On Compound
Where this term does real work — and where the decisions get made.
Sources
Last reviewed July 2026 by Compound Editorial. Definitions are educational and not project-specific engineering or medical advice.