Why Ventilation Wastes Energy
Buildings need fresh air, but exhausting conditioned indoor air and bringing in untreated outdoor air can waste a large share of heating and cooling energy. In cold weather the incoming air must be heated; in hot weather it must be cooled. Air-to-air heat recovery closes that gap.
How Air-to-Air Recovery Works
An air-to-air heat exchanger transfers energy between the outgoing exhaust stream and the incoming supply stream without mixing the two airstreams. Sensible recovery moves heat only; enthalpy, or total, recovery also moves moisture, which is valuable in humid climates.
Two Common Designs
- Plate exchangers: stationary aluminium or polymer cores, simple and reliable, good when the two streams must stay fully separated.
- Rotary wheels: a spinning desiccant-coated wheel that stores and releases heat and moisture; high efficiency but with some cross-leakage between streams.
Where It Pays Off
Recovery is most valuable in buildings with high air-change rates: schools, offices, hospitals, and labs. In cold climates, recovering heat from exhaust can cut heating demand by a third or more.
Sizing and Control Tips
- Match effectiveness to climate: higher in cold regions, balanced against fan energy.
- Use bypass dampers in shoulder seasons so free cooling is not blocked.
- Specify frost protection, such as preheat or exhaust recirculation, for very cold sites.
- Keep filters clean; fouling is the main cause of lost performance.
Bottom Line
For most ventilated buildings, air-to-air recovery is one of the shortest-payback energy upgrades available. The hardware is mature, maintenance is low, and the savings recur every heating and cooling season.
Frequently Asked Questions
How does air-to-air recovery reduce HVAC energy?
It transfers energy from the outgoing conditioned exhaust to the incoming fresh air, so the heating or cooling system only makes up the remaining difference rather than conditioning 100 percent outside air.
What is the difference between sensible and total recovery?
Sensible recovery moves heat only. Total, or enthalpy, recovery also transfers moisture, which is valuable in humid climates where both temperature and humidity loads are high.
Which design suits buildings better, plate or rotary?
Plate exchangers are simple, leak-tight, and good for moderate airflows. Rotary wheels suit larger volumes and can recover humidity, at the cost of slight stream carry-over.
Does recovery also improve comfort?
Yes. By pre-conditioning ventilation air, it stabilizes indoor temperature and humidity and reduces the size of the heating and cooling plant needed.
Frequently Asked Questions
How does air-to-air recovery reduce HVAC energy?
It transfers energy from the outgoing conditioned exhaust to the incoming fresh air, so the heating or cooling system only makes up the remaining difference rather than conditioning 100 percent outside air.
What is the difference between sensible and total recovery?
Sensible recovery moves heat only. Total, or enthalpy, recovery also transfers moisture, which is valuable in humid climates where both temperature and humidity loads are high.
Which design suits buildings better, plate or rotary?
Plate exchangers are simple, leak-tight, and good for moderate airflows. Rotary wheels suit larger volumes and can recover humidity, at the cost of slight stream carry-over.
Does recovery also improve comfort?
Yes. By pre-conditioning ventilation air, it stabilizes indoor temperature and humidity and reduces the size of the heating and cooling plant needed.
Specify the right heat exchanger
Our engineers size the core to your airflow, temperature and pressure-drop budget, and select plate, rotary or heat-pipe recovery by application. Read the heat exchanger guide or contact us for a specification.
Related products
Plate, wheel or pipe recovery for HVAC and ventilation.
Stationary, high-surface-area cores for air and liquid.
High-effectiveness energy recovery for large airflows.
Passive, fully separated streams for clean applications.