Air-to-Air Heat Recovery Units: Types, Specs and Selection Guide

An air-to-air heat recovery unit captures thermal energy from exhaust air and transfers it to incoming fresh air, cutting heating and cooling loads without mixing the two airstreams. This guide covers what these units contain, the main types, the specifications that matter, and how to choose one for HVAC or industrial duty.

What is inside an air-to-air heat recovery unit

A complete unit is more than the exchanger core. Typical components are:

• Heat exchanger core — plate, rotary wheel, heat pipe or run-around coil.
• Fans — supply and exhaust fans sized to the design airflow.
• Cabinet — insulated sheet-metal enclosure, often double-wall for low leakage.
• Filters — supply and exhaust filtration that protects the core and indoor air.
• Controls — temperature and frost sensors, bypass dampers and a controller.

For the full topic map, see our Heat Recovery Guide.

Main types of recovery units

• Plate (static) units — simple, no moving parts, best for clean separated streams. Our applications overview shows where they fit.
• Rotary wheel units — higher effectiveness and optional moisture transfer; watch leakage. See rotary vs plate.
• Heat-pipe units — passive and freeze-safe for harsh duty.
• Run-around coil units — separate coils when streams are far apart or must never mix.

Specifications that matter

• Recovery effectiveness — typically 60–85 percent for sensible plate units.
• Airflow (m³/h or cfm) — match the ventilation or process rate.
• Leakage — plate units keep streams separate; rotary wheels have a small carryover.
• Pressure drop — lower means lower fan energy.
• Core material — aluminum, stainless steel or polymer; see material selection.

How to select a unit

1. Fix the airflow and the temperature difference between exhaust and supply.
2. Choose the core type from contamination and moisture needs.
3. Size the core with a sizing calculation for target effectiveness at acceptable pressure drop.
4. Confirm frost control for cold-climate exhaust.

For ventilation-only duty, compare with a dedicated HRV system.

Frequently asked questions

What is an air-to-air heat recovery unit?
It is a packaged device with a heat exchanger core, fans, filters and controls that transfers heat between outgoing and incoming air to reduce heating and cooling energy.

What recovery effectiveness can I expect?
Sensible plate units commonly reach 60–85 percent; rotary and enthalpy wheels can be higher and also move moisture.

Plate or rotary for a recovery unit?
Use plate for clean streams and simple maintenance; use rotary when you need higher effectiveness or latent recovery and can accept small leakage.

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