Across jurisdictions, building codes increasingly mandate energy recovery once a system serves enough outdoor air. This overview compares the main regimes so a designer can specify one core that clears them all.
Minimum Effectiveness by Regime
| Regime | Trigger | Minimum recovery |
|---|---|---|
| ASHRAE 90.1-2022 (US) | ≥ 5,000 CFM and ≥ 70% OA | 50% enthalpy (AHRI 1060) |
| IECC / most US state codes | adopt 90.1 by reference | same 50% floor |
| California Title 24 (US) | high OA fractions, large systems | 50%+ sensible, climate-tuned |
| EU Ecodesign 1253/2014 | units ≥ 30 W fan power | 73% (ηt), 68% run-around |
| EU EPBD 2024/1275 | ZEB by 2030 (policy driver) | recovery expected, not a fixed % |
Reading the Differences
- The US rules trigger on system size and outdoor-air fraction; the EU rule triggers on equipment placed on the market and sets an absolute 73% thermal efficiency.
- California Title 24 tightens the sensible floor in cold climates and ties recovery to economizer controls.
- The EPBD does not state a percentage but makes recovery the practical path to a fossil-free, near-zero-energy building — see EPBD zero-emission buildings.
One Core, Many Codes
Specifying a core at 70–75% enthalpy effectiveness clears the US 50% floor, the EU 73% Ecodesign floor, and most Title 24 climate tiers at once. Use the test standards to confirm the number is measured on the right basis, and the ASHRAE 90.1 and Ecodesign articles for the exact exceptions. The result is a single specification that satisfies auditors on both sides of the Atlantic.
Practical Specifying Strategy
The cleanest way to satisfy every regime is to specify one core at 70 to 75% enthalpy effectiveness and confirm its measured value on the relevant test basis. That single choice clears the U.S. 50% floor, the EU Ecodesign 73% thermal floor, and most California Title 24 climate tiers simultaneously, which matters for manufacturers selling across markets. The trap is mixing metrics: ASHRAE and Ecodesign both quote effectiveness but define it at different conditions and for different streams, so compare like with like using the named standard. Exceptions also vary, lab and grease exhaust are exempt in the U.S., but the EU rule is about equipment placed on the market, so a project’s exceptions should be listed explicitly. Finally, remember that effectiveness without controlled pressure drop can backfire; a core that needs a much larger fan may erase its own saving, which is why fan-power limits bind the two together.
Frequently Asked Questions
How do U.S. and EU recovery mandates differ?
U.S. rules trigger on system size and outdoor-air fraction with a 50% floor, while the EU rule triggers on equipment sold and sets a 73% thermal efficiency.
Can one core satisfy all jurisdictions?
Yes. A core at 70 to 75% enthalpy effectiveness typically clears U.S., EU Ecodesign, and most Title 24 tiers at once.
Why must pressure drop be considered with effectiveness?
A more effective core needing a much larger fan can erase the energy saving, which is why fan-power limits bind the two together.
What exceptions are common?
Lab fume-hood, hazardous, and grease exhaust are commonly exempt in the U.S., while the EU rule instead governs equipment placed on the market.