The Passive House (Passivhaus) standard — from the Passive House Institute (PHI) in Darmstadt — is the most demanding envelope-and-services benchmark in buildings, and continuous ventilation with heat recovery is mandatory. This article covers the recovery requirements and how they compare with code minimums.
Core Recovery Requirement
| Metric | PHI limit |
|---|---|
| Sensible heat recovery efficiency (HRV/ERV) | ≥ 75% (most certified units exceed 80–90%) |
| Specific fan power | ≤ 0.45 Wh/m³ (≤ 0.765 W/CFM) |
| Airtightness (new build) | n50 ≤ 0.6 h−1 at ±50 Pa |
| Heating demand | ≤ 15 kWh/m²/year, or peak ≤ 10 W/m² |
An airtight envelope makes mechanical ventilation unavoidable for IAQ, and the 75% floor means incoming air is pre-conditioned to within a few degrees of indoor temperature — fresh air with minimal energy penalty. A summer bypass lets the core be skipped in mild weather.
EnerPHit (Retrofit)
The PHI retrofit pathway, EnerPHit, relaxes the envelope but keeps recovery strict:
- Heating demand ≤ 25 kWh/m²/year (or airtightness ≤ 1.0 ACH50).
- Minimum heat recovery efficiency ≥ 75% (UK climate-specific tables set 75–80% depending on zone).
- Triple-glazed windows (U ≤ 0.80 W/m²K) and minimal thermal bridging.
PHI vs PHIUS+
In North America, PHIUS+ (Chicago) offers climate-specific targets (CORE, ZERO, REVIVE families) optimized for carbon and cost per climate zone, using a different energy model. Both certify buildings, designers, and components independently.
How It Stacks Against Codes
A 75% Passive House floor is far above the ASHRAE 90.1 50% minimum and the EU Ecodesign 73% equipment threshold — though Ecodesign measures thermal efficiency (ηt) while PHI measures sensible. For critical ventilation, a non-rotating membrane core can meet the sensible floor without cross-contamination; a wheel does too but needs the frost and leakage care in wheel troubleshooting. See the enthalpy vs membrane comparison for the device trade-off.
Frequently Asked Questions
What recovery efficiency does Passive House require?
At least 75% sensible heat recovery, with most certified units exceeding 80 to 90%, and specific fan power at or below 0.45 Wh per cubic meter.
Why is recovery mandatory in Passive House?
The envelope is so airtight that mechanical ventilation is required for indoor air quality, and the 75% floor pre-conditions incoming air with minimal energy penalty.
What is EnerPHit?
The PHI retrofit pathway, which relaxes the envelope but keeps recovery strict at 75% or more and adds airtightness and window requirements.
How does PHI compare with PHIUS+?
PHIUS+ in North America uses climate-specific targets and a different energy model, while both certify buildings and components independently.