An air-to-air heat exchanger transfers heat between two air streams without mixing them — outgoing exhaust pre-conditions incoming fresh air. This guide is the hub for the technology: how each core type works, what sets effectiveness, and how to take a duty from a blank sheet to a sized, certifiable unit.
How it works
Two streams flow past a conductive surface (plates) or through a rotating matrix (wheel) or via a two-phase loop (heat pipe). The warm stream gives up heat to the cold one; in an ERV the same surface also moves moisture. Recovered energy is simply the temperature drop achieved times the airflow — try it on the savings calculator.
Core types
| Type | Transfers | Best for | Guide |
|---|---|---|---|
| Plate (counter/cross) | Heat | Clean air, high effectiveness, simple | Plate vs rotary |
| Rotary wheel | Heat + moisture | Highest effectiveness, ERV duty | Thermal wheel |
| Heat pipe | Heat (no mix) | Streams must not cross | Heat pipe |
| Run-around coil | Heat (no mix) | Streams far apart | Run-around coil |
What drives performance
- Effectiveness — share of recoverable heat moved (see efficiency factors and the ε-NTU tool).
- Face velocity — sets size vs pressure drop.
- Material — aluminium, stainless or polymer (see materials).
- Frost — cold-climate exhaust needs control (see frost control).
From duty to unit
- Define airflow, temperatures, hours — sizing tool.
- Pick type & material — selector / checklist.
- Read the datasheet at your conditions — datasheet guide.
- Confirm certification — AHRI / Eurovent / CE.
- Prove the economics — economics guide and payback tool.
Related hubs
- Applications guide — where recovery pays off.
- Economics guide — payback, lifecycle, carbon.
- ERV vs HRV · Enthalpy vs sensible · HVAC glossary.
Sizing an air-to-air core?
Send your duty and we will return a sized unit with a payback estimate.
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