Quick answer
A heat recovery ventilator (HRV) is a balanced ventilation unit that exhausts stale indoor air and brings in an equal flow of fresh outdoor air, passing both streams through a heat exchanger so the outgoing air warms or cools the incoming air without mixing them; it transfers heat (sensible energy) only, not moisture.
HRVs give a tight house the fresh air it needs while recovering much of the heat that ventilation would otherwise waste.
Quick facts
The key facts about Heat Recovery Ventilator (HRV), with sources:
- Transfers
- Sensible heat only; not moisture 1
- Most common core
- Fixed-plate cross-flow or counterflow heat exchanger 1
- Airflow
- Balanced: supply roughly equals exhaust
- Efficiency metric
- Adjusted Sensible Recovery Efficiency (ASRE), certified by HVI 3
- Ventilation standard (homes)
- ANSI/ASHRAE 62.2-2025 2
- Airflow testing
- ANSI/RESNET/ICC 380 covers mechanical ventilation airflow 4
Key takeaways
- An HRV swaps stale air for fresh air and keeps much of the heat, using a heat exchanger.
- It moves heat only. An ERV moves heat and moisture 1.
- HRVs suit cold climates with long heating seasons, where indoor air tends to be dry in winter but humidity is not a big summer issue.
- HVI rates HRV efficiency as Adjusted Sensible Recovery Efficiency (ASRE); higher is better 3.
- An HRV is ventilation, not heating or cooling. It does not replace the furnace or heat pump.
What an HRV does
Modern homes are built tight to save energy. That keeps heat in, but also keeps moisture, odors and pollutants in. Homes still need fresh air. ASHRAE Standard 62.2, now in its 2025 edition, sets minimum ventilation for dwellings through whole-house ventilation, local exhaust and source control 2.
An HRV provides whole-house ventilation in a balanced way. One fan pulls stale air from kitchens, baths or a central return and sends it outside. Another fan pulls in the same amount of outdoor air. Both streams pass through a core where heat moves from the warmer stream to the cooler one.
Natural Resources Canada sums up the key difference: an HRV transfers sensible heat only, while an ERV recovers both sensible and latent heat 1. Sensible heat changes temperature; latent heat is carried in water vapor.
How air moves through an HRV in winter
- Warm, stale indoor air → enters the core
- Cold fresh outdoor air → enters the core in separate passages
- Heat crosses the plates → fresh air warms, stale air cools
- Cooled stale air → exhausted outside; condensate drains
- Tempered fresh air → delivered to rooms or the HVAC return
Frost, condensate and balance: the three things that make or break an HRV
In winter, warm indoor air carries moisture. As it gives up heat in the core, some of that moisture condenses. That is why an HRV needs a drain line, usually with a trap, run to a floor drain or pump.
In very cold weather, that condensate can freeze inside the core and block airflow. HRVs handle this with a defrost strategy: some briefly recirculate indoor air, some shut off the fresh-air fan for a few minutes, and some preheat the incoming air. Pick a unit whose frost control suits your coldest weather.
Balance is the third piece. Supply and exhaust should be close to equal. If exhaust is much higher, the house is pulled into negative pressure, which can draw in air through leaks or, in a home with a fireplace or older gas appliance, cause backdrafting. A contractor balances the unit with airflow measurements at start-up.
HRV types and setups
| Type or setup | How it works | Notes |
|---|---|---|
| Cross-flow plate core | Streams cross at right angles through plates | Common, simple 1 |
| Counterflow plate core | Streams run opposite, longer contact | Often higher recovery |
| Dedicated ducts | HRV has its own supply and exhaust ducts | Best distribution; more duct work |
| Tied to HVAC return | Fresh air fed into the air handler | Simpler; needs fan interlock |
| Ductless, through-wall | Small units in pairs or alone | For single rooms or retrofits |
HRV vs ERV vs other ventilation
| System | Recovers | Best fit | Watch for |
|---|---|---|---|
| HRV | Heat only | Cold climates; homes with winter moisture to remove | Condensate drain; frost control |
| ERV | Heat and moisture | Humid summers or very dry winters | Does not dehumidify on its own |
| Exhaust-only fans | Nothing | Simple, low cost | Pulls air from leaks; no recovery |
| Supply-only | Nothing | Some mild climates | Can push moisture into walls in cold climates |
| Demand-controlled ventilation | Depends on the unit | Varies airflow with need | Needs sensors and controls |
Example: how much heat an HRV keeps in
A home ventilates 60 cubic feet per minute (CFM) continuously in winter. Indoors 70°F, outdoors 20°F. The HRV in this example recovers 70% of the sensible heat (an example figure; check the unit’s HVI-certified rating). Air carries about 1.08 BTU/h per CFM per °F of temperature difference (a standard HVAC engineering constant for sea-level air).
| Case | Math | Heat lost to ventilation |
|---|---|---|
| No recovery (exhaust fan) | 1.08 × 60 × (70 − 20) | 3,240 BTU/h |
| HRV at 70% recovery | 3,240 × (1 − 0.70) | about 970 BTU/h |
| Heat kept in by the HRV | 3,240 − 970 | about 2,270 BTU/h |
Over a cold month, that difference adds up. The HRV’s own fan power is not counted here; HVI’s ASRE metric accounts for fan energy when rating efficiency 3. Ask your designer to size airflow to ASHRAE 62.2 2.
Where you find HRVs
- In new, tight homes in cold climates, often required to meet a ventilation code.
- In deep energy retrofits after air sealing.
- In a basement or mechanical room, with insulated ducts to outdoors.
- On the HVI-Certified Products Directory with ASRE ratings 3.
- On HERS ratings, where ventilation airflow may be tested under RESNET/ICC 380 4.
Benefits and trade-offs
Benefits
- Steady fresh air in a tight house.
- Recovers much of the heat ventilation would waste.
- Balanced airflow; does not depressurize the house.
- Helps remove winter moisture in cold climates.
Trade-offs
- Needs a condensate drain and frost protection in cold weather.
- Ducts and space for the unit.
- Filters and core need regular cleaning.
- In humid summers it brings in moisture; an ERV may fit better.
What an HRV cannot do
An HRV ventilates; it does not heat, cool or dehumidify a house on its own. In humid summers, it brings in outdoor moisture along with fresh air. A dehumidifier or the AC must handle that.
It also cannot fix a leaky house. In a drafty home, air already leaks in and out without recovery; the HRV adds little until the house is sealed.
Cost drivers and lifespan
Cost depends on the unit’s capacity and efficiency, duct layout (dedicated ducts cost more than tying into the HVAC), wall or roof penetrations, controls and electrical work. Retrofits in finished homes cost more than new construction.
HyreHVAC publishes no prices without enough dated quotes. See ventilation services for what an install covers.
How an HRV is designed and installed
- Find required ventilation airflow under ASHRAE 62.2 or the local code 2.
- Choose HRV or ERV by climate and humidity.
- Pick a unit with HVI-certified ratings at the needed airflow 3.
- Plan ducts: fresh air to living areas, exhaust from kitchens and baths, outdoor hoods well apart.
- Install with a condensate drain and frost control.
- Balance supply and exhaust and measure airflow; RESNET/ICC 380 covers ventilation airflow testing 4.
Maintenance
- Clean or replace filters every few months, or as the maker says.
- Clean the core per the manual, often yearly.
- Check outdoor hoods for leaves, snow and nests.
- Make sure the condensate drain flows.
- Rebalance airflow if rooms or ducts change.
Warning signs
- Condensation on windows or musty smells: ventilation may be too low.
- Cold drafts from supply grilles: frost control or balance issue.
- Water around the unit: blocked drain.
- Very dry winter air: ventilation may be too high for the house.
- Call a ventilation contractor for balance or electrical issues.
Standards and codes
ANSI/ASHRAE 62.2-2025 sets minimum ventilation for dwelling units 2. Many state codes based on the IRC and IECC require mechanical ventilation in new homes; adoption and editions vary, and DOE tracks them 5.
ANSI/RESNET/ICC 380 covers testing ventilation airflow, envelope and duct airtightness 4. HVI certifies HRV and ERV performance and publishes ASRE ratings 3.
Misconceptions
- Myth An HRV heats the house.
- Reality It recovers heat from exhaust air; it does not add heat.
- Myth HRVs dry out a house too much.
- Reality Only if over-ventilating; airflow should match the standard.
- Myth An HRV and an ERV are the same.
- Reality An ERV also moves moisture 1.
- Myth Opening a window does the same thing.
- Reality Windows ventilate without recovery or control.
Climate decides HRV vs ERV
In cold-winter states with modest summer humidity, such as Washington or Ohio, HRVs are common. In humid states such as Florida, Georgia or North Carolina, an ERV usually fits better because it limits moisture brought in during cooling season. Climate zone and degree days help decide.
Do you need an HRV?
If your home is tight, as in new construction or after serious air sealing, and you live where winters are long, an HRV is a strong choice. If summers are humid, compare an ERV.
Next step: see indoor air quality services, or read our smoke and filters research if outdoor air quality is a concern.
Questions about Heat Recovery Ventilator (HRV)
What does a heat recovery ventilator do?
It replaces stale indoor air with fresh outdoor air at a balanced rate, passing both streams through a heat exchanger. In winter the outgoing air warms the incoming air; in summer it cools it. The streams do not mix, and an HRV transfers heat only, not moisture.
What is the difference between an HRV and an ERV?
An HRV transfers sensible heat only. An ERV transfers both heat and moisture. HRVs suit cold climates where winter moisture needs removing. ERVs suit humid summers or very dry winters, because they limit how much moisture moves between the air streams.
Do I need an HRV?
You may if your home is tight, such as new construction or after air sealing, and needs mechanical ventilation. Many codes require whole-house ventilation in new homes. In cold climates an HRV recovers heat that exhaust fans would waste.
How efficient is an HRV?
HVI certifies HRVs and rates them by Adjusted Sensible Recovery Efficiency (ASRE), which accounts for heat transfer and fan airflow. Higher is better. Compare ASRE at the airflow your home needs, using the HVI-Certified Products Directory.
How often should HRV filters be cleaned?
Follow the maker’s schedule; many suggest checking filters every few months and cleaning the core about once a year. Dirty filters cut airflow and recovery. Also check outdoor hoods for blockages and make sure the condensate drain flows.
Can an HRV freeze in winter?
Yes, the core can frost in very cold weather because moist exhaust air cools below freezing. HRVs use defrost strategies such as recirculation or brief shutdowns. Make sure your unit’s frost control suits your climate.
Does an HRV replace my furnace or air conditioner?
No. An HRV only ventilates and recovers heat. Your furnace, heat pump or air conditioner still heats and cools. An HRV may connect to the HVAC ducts, but it is a separate system.
How much fresh air should an HRV supply?
Enough to meet ASHRAE 62.2 or your local code, which sets airflow by house size and number of bedrooms. Too little leaves stale air; too much wastes energy and can over-dry the house in winter. Have the airflow measured after install.
Where should an HRV be installed?
Usually in a basement, mechanical room or conditioned attic space, close to an outside wall so the fresh-air and exhaust ducts are short. Outdoor hoods should be well apart so exhaust is not pulled back in. A drain must be nearby for condensate. Ducts to the outdoors should be insulated.
Sources
- Natural Resources Canada, CanmetENERGY fact sheet: Reducing Energy Waste with Heat Recovery, retrieved .
- ASHRAE, Standards 62.1 and 62.2 (2025 editions), retrieved .
- Home Ventilating Institute (HVI), Publications (ASRE consumer and builder guides), retrieved .
- RESNET, HERS Index (references ANSI/RESNET/ICC 380), retrieved .
- U.S. DOE, Building Energy Codes Program, retrieved .
Expert review
Written by the HyreHVAC Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: HRV vs ERV definition from NRCan’s heat recovery fact sheet; ventilation standard from ASHRAE; efficiency metric from HVI; testing standard from RESNET. The heat-loss example uses a standard air constant and a labelled example recovery rate.
Suggest a correction. We fix errors and say what changed.