Service guide
ERV or HRV: a moisture decision, not a climate map
Both bring outdoor air in and recover energy from the air going out. Only one also moves water vapor, and that difference decides the choice.
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Written by HYRE HVAC Research Desk Primary-source research, data analysis and fact checking
The short version
A balanced ventilator brings outdoor air in and sends indoor air out at about equal rates, recovering energy between the two. The difference between the two types is moisture. An HRV moves heat only.
An ERV also moves water vapor. So the choice depends on whether your house needs to hold humidity in or get it out, measured against EPA’s 30–50% range.
Where this page stops, stated first
Two limits, and the second one is unusual enough to be worth stating plainly rather than leaving a reader to notice the absence.
Whether your jurisdiction requires whole-house mechanical ventilation, and at what rate, depends on the code edition it has adopted. ASHRAE 62.2 is a proprietary standard and the ICC code text is not publicly retrievable, so neither was readable when this page was written.
Rather than print a formula from recall at an edition we cannot confirm, we say this: ask your building department, and make your contractor tell you which code and edition their design answers to.
A ventilator is ducted through the building envelope and shares a house with combustion appliances. There is no homeowner step here. And HyreHVAC holds no dataset of installation invoices, so no range is printed.
Ventilation and filtration solve different problems and are frequently conflated in proposals. Filtration is covered by the filter selector and the wildfire smoke research.
Tighter houses are why this equipment exists at all
An older, leaky house ventilates itself by accident. Air moves through gaps in the envelope whenever there is a difference in temperature or wind pressure, which is wasteful but does mean the indoor air is continually being replaced.
Sealing a house removes that accident. The energy saving is real and the air exchange that came with it is gone, so the replacement has to be deliberate rather than incidental.
That is the whole case for balanced ventilation: it supplies and exhausts on purpose, at a rate somebody chose, and recovers most of the energy that used to leave with the air.
HyreHVAC analysis: this is also why the question arrives at the wrong moment for most people. It surfaces after an envelope upgrade or a new build, when the budget is already committed — rather than during the work, when the ducting would have been far cheaper to install.
The difference between an ERV and an HRV is water vapor
Everything else about the two is broadly the same: balanced supply and exhaust, a core that transfers energy between the streams, ducting, filters and a control. The distinguishing feature is moisture.
| HRV — heat recovery ventilator | ERV — energy recovery ventilator | |
|---|---|---|
| Transfers heat | Yes | Yes |
| Transfers water vapor | No | Yes — DOE: “In addition to exchanging heat, ERVs transfer a certain amount of water vapor; this helps the humidity inside the home stay more constant.” |
| Effect on indoor humidity in winter | Dries the house faster, because incoming dry air is not humidified | Retains more indoor moisture, which helps a house that gets too dry |
| Effect in a humid summer | Brings outdoor moisture straight in with the air | Moderates how much outdoor moisture arrives with the air |
| Suits a house that | Runs damp, or has a moisture source it is still fighting | Runs dry in winter, or sits in a humid climate |
DOE describes what both do seasonally: “They reduce the costs of heating ventilated air in the winter by transferring heat from the warm inside exhaust air to the colder outside supply air. In the summer, the inside air cools the warmer supply air to reduce cooling costs.”
HyreHVAC analysis: the common shorthand — ERV in the South, HRV in the North — is a reasonable first guess and a poor final answer, because it describes the climate rather than the house.
A tight, damp house in a cold climate and a dry, leaky house in a warm one are both common, and both are the exception the shorthand gets wrong.
Ventilation is EPA’s second strategy, and the order matters here
EPA ranks three approaches to indoor air quality and is explicit about the first: “For most indoor air quality problems in the home, source control is the most effective solution.”
Ventilation is the second — “Another approach to lowering the concentrations of indoor air pollutants in your home is to increase the amount of outdoor air coming indoors.”
The distinction is between dilution and removal. A ventilator lowers the concentration of whatever is in the air by mixing it with outdoor air. It does not stop the thing producing it.
So a house with an unsealed crawlspace, an unvented appliance, or a bathroom fan discharging into the attic does not have a ventilation problem to solve with equipment. It has a source, and the source will keep producing at exactly the same rate after the ventilator is installed.
HyreHVAC recommendation: find and fix the source first. Where one exists, that is both cheaper and the strategy EPA puts ahead of this one.
When balanced ventilation is the right purchase
The strong cases are about the envelope. The weak ones are usually a source problem wearing a ventilation costume.
- Right — a new or recently tightened house
- Air sealing, new windows, spray foam or a blower-door-tested build all remove the accidental air exchange the house used to get. Replacing it deliberately is the entire purpose of this equipment.
- Right — persistent winter condensation in a tight house
- Water on the inside of windows in cold weather usually means moisture is being generated faster than the house can shed it. In a tight house, that is a ventilation problem. In a leaky one it is more often a source problem.
- Right — stale air that does not track with any identifiable source
- Where a house simply feels stuffy, and no smell, damp or appliance points at a cause, dilution is a reasonable answer rather than a substitute for a diagnosis.
- Not yet — there is an unfixed moisture or pollutant source
- An unsealed crawlspace, negative grading, a leak, or extraction that vents into the attic. EPA puts source control first, and a ventilator run against a source is an operating cost with no end date.
- Not yet — the bathroom and kitchen fans do not work
- Spot extraction is the cheapest ventilation in the house and it is very often broken, disconnected or discharging into a roof space. Confirm they actually move air outdoors before adding a whole-house system to compensate.
- Probably not — an older, leaky house with no measured problem
- HyreHVAC analysis: a house that still ventilates itself by accident is unlikely to get its money back from equipment that formalises what it is already doing for free. Seal first, then ventilate deliberately — in that order, not the reverse.
What belongs in the quote
A balanced ventilator is a ducted appliance with two paths through the building envelope. These are the items that separate a designed installation from a box on a wall.
Ask directly, and expect a specific answer naming the standard and the year. This is the item this page cannot give you, so it is the one most worth extracting from whoever is quoting.
The reason should be about your house — measured indoor humidity, whether it runs damp or dry, what the envelope is like — and not only about the climate zone. If the answer is a region, ask what readings it is based on.
Fully ducted with its own supply and return points, or sharing the existing duct system. Sharing is cheaper and ties ventilation to whether the air handler happens to be running, which is a consequence that should be explained rather than discovered.
An intake near a driveway, a dryer vent, a combustion flue or a rubbish store will supply the house with exactly what is there. Location is a design decision, not an installation convenience.
Supply and exhaust measured and balanced against each other, with the results on the paperwork. An unbalanced "balanced" ventilator pressurises or depressurises the house, and in a house with combustion appliances depressurisation is a safety question, not a comfort one.
Both streams have filters and both need changing. Where the unit is put decides whether that actually happens for the next fifteen years.
Where to go from here
Two routes, depending on what your house is actually doing.
If the house runs damp
Measure before you choose equipment. EPA’s guidance is to “keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity”, and a week of hygrometer readings will tell you which side of that you are on.
A damp house usually wants moisture removed rather than retained, which argues against an ERV and often against ventilation as the first purchase at all. See whole-home dehumidifier installation.
If the complaint is air quality generally
Ventilation is one of three strategies and the second of them. Whether an assessment is even worth buying, and the services EPA declines to recommend routinely, are covered on indoor air quality assessment.
If the problem is particles or smoke rather than staleness, the filter selector is the cheaper and more direct answer.
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Questions
What is the difference between an ERV and an HRV?
Do I need whole-house mechanical ventilation by code?
Will an ERV fix my damp house?
Is a ventilator the same as an air purifier?
Can an ERV or HRV share my existing ductwork?
Why does commissioning matter on this equipment?
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HYRE HVAC Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a sales floor. We read the federal microdata file, the statute or the manufacturer data sheet ourselves, and we publish the figure with the document it came from and the date we retrieved it.
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The counts below are generated from the published pages themselves, last counted September 28, 2026, and they are what we have actually published rather than what we intend to.
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Data as of DOE Building Science Education ventilation page read September 16, 2026; EPA indoor air quality and mold pages as recorded September 16, 2026. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
HyreHVAC is a research and referral site. We do not perform HVAC work, design ventilation systems or install equipment, and nothing on this page is a code determination for your jurisdiction. Ventilation requirements depend on the code edition your local authority has adopted; confirm them with your building department.