Quick answer: An HRV (Heat Recovery Ventilator) transfers only heat between outgoing and incoming air. An ERV (Energy Recovery Ventilator) transfers both heat and moisture. In the Pacific Northwest’s damp, mild climate, the choice depends on your home’s airtightness and indoor humidity — many tight PNW homes do well with an ERV, but some prefer an HRV to expel excess moisture.
📄 Table of Contents
TL;DR: Both bring fresh air into an airtight home while recovering energy. The key difference is moisture: HRV keeps humidity out of the exchange; ERV moderates it. For Seattle’s wet winters, the right pick depends on how tight your home is and whether you tend to have too much or too little indoor humidity. An architect or mechanical designer should size and select it as a system, not a guess.
Why tight homes need mechanical ventilation
Modern energy-efficient homes are deliberately airtight to save energy — but a sealed home can’t “breathe” on its own. Without controlled ventilation, you get stale air, excess moisture, and indoor air-quality problems. Balanced mechanical ventilation (HRV or ERV) solves this by continuously exchanging stale indoor air for filtered fresh air while recovering most of the energy that would otherwise be lost. It’s essential in passive house and high-performance homes.
HRV vs ERV: the core difference
| Feature | HRV (Heat Recovery) | ERV (Energy Recovery) |
|---|---|---|
| Transfers heat | Yes | Yes |
| Transfers moisture | No | Yes |
| Best for | Homes that need to expel excess humidity | Homes that benefit from moderating humidity |
| Winter effect | Removes moist indoor air | Retains some indoor humidity |
| Typical PNW use | Very airtight homes, high indoor moisture | Most tight homes seeking balanced humidity |
How to choose for a Seattle / PNW home
The Pacific Northwest is humid outside but indoor moisture (cooking, showers, people) is the bigger driver in winter. The decision usually comes down to:
- Indoor humidity tendency: If your home runs humid (lots of occupants, cooking, drying), an HRV that expels moisture may help. If it runs dry in winter, an ERV that retains some humidity is more comfortable.
- Airtightness: The tighter the home, the more critical balanced ventilation becomes, and the more an ERV’s humidity moderation is felt.
- Whole-system design: Duct layout, filtration (MERV rating), and controls matter as much as HRV-vs-ERV. The unit is one part of a designed system.
There’s no universal “PNW always uses X” — it’s a home-specific decision made during design.
Common mistakes to avoid
- Treating it as an afterthought instead of designing it into the home early
- Undersizing or oversizing the unit for the home’s volume and occupancy
- Ignoring filtration and duct design, which affect comfort and air quality
- Choosing HRV vs ERV on a rule of thumb instead of the home’s actual humidity profile
Designing ventilation into your home
Ventilation works best when it’s planned alongside insulation, air-sealing, and the floor plan — not bolted on later. We integrate balanced ventilation into our custom home and sustainable design work. Talk to Piper Cole Architects about a healthy, efficient home.
FAQ
What is the difference between an HRV and an ERV? An HRV transfers only heat between incoming and outgoing air; an ERV transfers both heat and moisture. The moisture transfer is the deciding factor.
Is an HRV or ERV better for the Pacific Northwest? It depends on your home. Many tight PNW homes use an ERV to moderate humidity, but homes with high indoor moisture may prefer an HRV to expel it. It’s a home-specific choice.
Do I need an HRV or ERV in an airtight home? Yes. Airtight homes need balanced mechanical ventilation to supply fresh air and control moisture; an HRV or ERV does this while recovering most of the energy.
Does an ERV help in winter? Yes. An ERV recovers heat and retains some indoor humidity, which improves comfort in dry winter conditions while still supplying fresh air.
Sources consulted: ASHRAE 62.2 residential ventilation standard; DOE/Building America guidance on HRV vs ERV by climate; Passive House ventilation principles; Piper Cole Architects high-performance home experience.
Ready to talk about your project?
Piper Cole Architects has designed 800+ Eastside projects since 2000. Get a free, no-pressure consultation with David Meade, AIA, NCARB.