In cold climates the exhaust side of a heat exchanger can fall below the frost point, and ice build-up raises pressure drop and can block the core. Enter your outdoor, exhaust and indoor conditions plus the core type to estimate whether a preheat coil, bypass damper or defrost cycle is required before you finalize the selection. This is a first-order screening tool; verify against EN 308 or AHRI 1060 test data and the project design conditions.
A quick screening tool for air-to-air heat exchangers in cold climates. Enter your air conditions and exchanger type to see whether frost or condensation is likely — and what to do about it.
Air conditions
Designing for a cold-climate project?
Our engineers can specify freeze protection — preheat coils, bypass strategies or heat-pipe selection — for your exact conditions.
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How to use this tool in a specification
These results are a first-pass screening aid. Confirm the duty point against certified test data (EN 308 / AHRI 1060), the applicable energy code, and the manufacturer datasheet before issuing a purchase specification. For a verified sizing, send us your airflow and temperatures.
Frequently asked questions
When does a heat exchanger frost up?
Frost forms when the cold exhaust-side surface temperature drops below 0 C AND below the exhaust air dew point. This typically happens in cold climates with humid indoor exhaust (kitchens, pools, labs) when outdoor air is below about -5 to -10 C depending on exchanger effectiveness.
Which heat exchanger type resists frost best?
Plate and rotary exchangers are most efficient but most frost-prone at the cold corner. Heat-pipe exchangers tolerate frost better and allow built-in frost-control strategies, though at lower effectiveness. The right choice depends on climate and exhaust humidity.
How do you prevent frost in an air-to-air heat exchanger?
Common methods: preheat the incoming outdoor air, recirculate a controlled fraction of exhaust air, use a summer/winter bypass, or select a heat-pipe unit with passive frost control. Our estimator shows whether mitigation is needed for your conditions.
What is the dew point used for here?
The dew point is the temperature at which moisture condenses out of air at a given humidity. If any surface in the exchanger falls below the exhaust-air dew point, condensation (or frost, if also below 0 C) occurs on that surface.
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Related: frost protection design, exchanger type comparison, climate-zone requirements · all heat recovery tools.