Select an MVHR unit for the calculated duct system, not merely the floor area. Its operating point after connecting ducts and filters matters.
Airflow and pressure
Balance supply to living spaces against extract from service rooms. Select the operating point on the fan curve, accounting for duct resistance and filter loading.
Efficiency and consumption
Compare heat recovery and electrical input at matching flows and test methods. A headline peak efficiency does not describe annual performance including preheating and frost protection.
Noise and filtration
Obtain duct and casing sound data and plan unit location, attenuators and vibration isolation. Check replacement filter availability, pressure drop and access for replacement.
Winter, summer and moisture
Clarify frost protection, condensate drainage, bypass operation and moisture recovery. A summer bypass creates no cooling by itself and does not replace an overheating assessment.
Common mistakes and acceptance
Selection at maximum free-air flow, placement above bedrooms and inaccessible filters undermine operation. Acceptance should include measured flows, balancing and settings handed to the owner.
| Item | Parameter | Check / result |
|---|---|---|
| Ducts | Flow and pressure | Operating point |
| Comfort | Sound and humidity | Modes |
| Service | Filters and drain | Access |
What this means for your project
Request unit selection together with the duct layout, acoustic measures and maintenance plan. Compare quotations against identical input requirements.
Sources and scope of review
- US DOE — HVAC whole-house ventilation
- DOE Building Science Education — Energy recovery ventilation
- PHI — Ventilation component certification criteria
Related reading
- Thermal Bridges: Where They Occur and Why They Matter
- Airtightness: What It Is and Why It Matters
- House Orientation: What Actually Affects Energy Balance