Quick answer
Modern energy codes make homes tight, and in the damp Pacific Northwest a tight home without planned ventilation traps moisture — the raw ingredient for condensation, musty smells, and mold. A heat recovery ventilator (HRV) solves it mechanically: stale, humid indoor air goes out, fresh filtered air comes in, and a heat-exchange core keeps most of the warmth you already paid for.
- Tight construction saves energy but traps moisture, CO2, and indoor pollutants unless ventilation is designed in.
- EPA guidance: keep indoor relative humidity below 60% — ideally 30–50% — to deny mold what it needs.
- An HRV exchanges stale indoor air for fresh outdoor air while recovering most of the outgoing heat.
- Condensation on winter windows is the classic PNW symptom that a home isn't exhausting enough moisture.
- ASHRAE 62.2 is the residential ventilation standard new tight homes are built against.
Why do tight homes have moisture problems in the PNW?
Everyday living releases a surprising amount of water vapor — cooking, showers, laundry, even breathing. Older, draftier houses leaked that moisture out through the walls along with your heat. A modern tight home holds onto both. In a dry climate that's mostly an energy win; in a marine climate where outdoor air spends half the year saturated, it means indoor humidity climbs with nowhere to go.
The consequences show up in a predictable order: condensation beading on winter windows, then musty odors in closets and corners, then visible mold on cold surfaces. The EPA's moisture guidance is blunt about the fix: keep indoor relative humidity below 60 percent — ideally between 30 and 50 percent — because controlling moisture is the only reliable way to control mold.
What does an HRV actually do?
A heat recovery ventilator is a continuously running appliance with two air streams that pass each other through a heat-exchange core without mixing. Stale, humid air from bathrooms and living space is exhausted outdoors; fresh outdoor air is filtered and delivered inside — and on the way, the outgoing warm air transfers most of its heat to the incoming cold air. You get constant fresh air without the energy penalty of just opening a window in January.
That heat recovery is what separates an HRV from the bath fans and range hood you already have. Exhaust-only fans depressurize the house and throw heated air away; an HRV ventilates in balance and keeps the warmth. In a climate with a long mild heating season like ours, that difference runs all winter, every winter. The EPA's residential ventilation guidance and ASHRAE Standard 62.2 define how much fresh air a home needs — tight new construction generally can't meet it without mechanical ventilation.
How do you know if your home needs one?
Signals we look for on assessments across Clark County:
- Persistent window condensation in winter — the house is holding more moisture than it exhausts.
- Musty smells in bedrooms overnight or in rarely opened rooms — stale air isn't turning over.
- A newer or recently air-sealed home — the tighter the shell, the more ventilation must be deliberate.
- Lingering cooking and bathroom odors, stuffiness, or morning headaches — classic low-air-exchange complaints.
An HRV isn't the answer to every moisture problem — a crawlspace issue or a failed bath fan is fixed at the source — so we diagnose before we prescribe. Ventilation also pairs tightly with duct health: delivering fresh air through leaky ducts wastes it, which is where our duct design & sealing guide picks up.
What does installation involve?
A typical retrofit places the HRV unit in a garage, utility room, or attic, with dedicated fresh-air supply and stale-air exhaust runs — often tied into existing ductwork where the layout allows. Sizing follows the home's volume and ASHRAE 62.2 airflow targets, not guesswork, and because we fabricate sheet metal in our own shop, odd routing problems get solved instead of compromised. Our HRV service page covers what we install, and filters need only simple seasonal cleaning — a habit our maintenance checklist folds in.
About this guide
Written and reviewed by the Home Energy Group team — a family-owned HVAC company celebrating 25 years of comfort & care across SW Washington and the Portland metro, licensed in Washington (WA LIC# HOMEEGI003J7) and Oregon (OR CCB# 184255), and an authorized Daikin & York dealer. Guidance reflects the systems we install and service every week. Last reviewed July 3, 2026.
Common questions
What's the difference between an HRV and an ERV?
Both exchange stale indoor air for fresh outdoor air through a heat-recovery core. An HRV transfers heat only; an ERV also transfers some moisture between the air streams. In the marine Pacific Northwest, where winter moisture removal is usually the goal, an HRV is the common recommendation — but the right choice depends on your home, which is what an assessment is for.
Will an HRV stop condensation on my windows?
If the condensation is caused by high indoor humidity — the usual case in tight PNW homes — continuous balanced ventilation typically resolves it by exhausting moist air before it condenses on cold glass. If the source is something else, like a crawlspace moisture problem, we fix that at the source first.
Does an HRV waste the heat I've paid for?
No — that's the point of it. The heat-exchange core transfers most of the heat from the outgoing stale air into the incoming fresh air, so you get continuous fresh air at a fraction of the energy cost of open-window or exhaust-only ventilation.
How much maintenance does an HRV need?
Very little: filter cleaning or replacement a few times a year and an occasional core rinse. We fold HRV checks into seasonal maintenance visits so it stays a set-and-forget system.
