What is an HRV?
Updated August 2026
An HRV, or heat recovery ventilator, is a ducted appliance that continuously swaps stale indoor air for filtered outdoor air while keeping most of the heat that would otherwise leave with it. Two airstreams pass on opposite sides of an aluminum or plastic core, close enough to trade heat but never mixing. Typical cores recover 60 to 85% of the temperature difference, so 10 degree outdoor air arrives near 55 degrees before the furnace touches it.
Where it is
Most units hang from mechanical-room or basement joists on rubber straps, roughly the size of a carry-on suitcase, with four duct collars across the face. Two insulated ducts run to a pair of hooded openings on an exterior wall, usually 6 feet apart so the exhaust is not immediately re-inhaled, and two run into the house, drawing from bathrooms and laundry and supplying bedrooms or the furnace return. A small condensate line drops from the bottom. The wall control looks like a thermostat with 20, 40, and 60 minute per hour settings, plus a boost button near the bathrooms.
What it does
Tight houses need mechanical ventilation because they no longer leak enough on their own. Below roughly 3 air changes per hour at 50 pascals, carbon dioxide, cooking moisture, and off-gassing from finishes accumulate, and opening a window in January is not a plan. An HRV runs a measured exchange, commonly 40 to 120 cubic feet per minute for a house, at a fraction of the heating penalty raw ventilation would carry. Failure announces itself through your nose and eyes first: cooking odors linger, bathroom mirrors stay fogged 20 minutes, windows sweat. The mechanical causes are packed filters, a core iced over because the defrost cycle quit, and an exterior hood screen matted with dryer lint or cottonwood.
Maintenance
Wash both filters every 3 months, pull and rinse the core once a year, and walk outside twice a year to clear the intake and exhaust hoods. That is 20 minutes of work protecting a $2,000 appliance. Since the unit shares a mechanical room and often a duct system with the air handler, fold it into the same visit: how often to clean an air handler. A puddle under an HRV is almost always its own condensate line, but rule out the bigger culprit in why an air handler leaks water.
What it costs to replace
A replacement HRV runs $1,500–3,500 installed, with a replacement core at $200–400 and a filter set at $20–60.
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Frequently asked questions
HRV or ERV: which one belongs in my house?
Match it to what your climate does to indoor humidity. An HRV transfers heat only, which suits cold, dry winters where you want to push excess indoor moisture out. An ERV also transfers moisture between the airstreams, which keeps summer humidity from riding in with the fresh air across the Southeast and keeps winter air from going bone dry in very cold, arid regions. Installed costs sit within a few hundred dollars of each other, so choose on climate rather than price.
Does an HRV replace bathroom exhaust fans?
In many designs, yes. A multi-port HRV pulls continuously from each bathroom and the laundry, with a boost switch for showers, and that satisfies code ventilation in most jurisdictions. What it handles poorly is a large slug of steam all at once, so a long hot shower can still fog the mirror. Kitchens are the exception nearly everywhere: grease and high volume need a dedicated range hood ducted outside, never tied into the HRV.
How much does an HRV cost to run?
Less than most people assume. A current unit with ECM motors draws 30 to 80 watts on low and maybe 120 on boost, which is $3 to $8 a month of electricity even running most of the day. The heating penalty is the smaller number: recovering 70 to 80% of the outgoing heat means you only condition the leftover 20 to 30% of ventilation air. Running it too little costs more in comfort than running it costs in dollars.
Does an older house need one?
Usually not, and a blower door test settles it. The test runs $150 to $400 and often comes free with an energy audit. A house above about 5 air changes per hour at 50 pascals already exchanges plenty of air through gaps, and adding an HRV before air sealing spends money on a leak you have not fixed yet. Seal first, retest, then add ventilation once the house is tight enough to need it.