Two Forms of Energy in Air
Air carries energy as dry-bulb heat (sensible) and as water vapour (latent). A sensible exchanger moves only temperature; an enthalpy exchanger moves both. The choice changes the whole system design.
Deep Selection Logic
- Dry or cold climate - sensible recovery is usually enough; moisture is not the bottleneck
- Hot, humid climate - latent load dominates; choose enthalpy recovery
- Mixed climate - check the cooling-coil load with and without moisture recovery
How to Quantify
Compute the latent load as the mass of condensate the coil must remove. If that load is large, enthalpy recovery (rotary wheel or membrane plate) typically halves dehumidification demand and shortens payback.
Decision Rule
If the humidity-ratio difference between streams is small, a sensible plate core is the cost-effective choice. If it is large and the cooling coil is oversized, move to enthalpy recovery.
How the Two Approaches Differ
When evaluating options for Sensible vs Latent (Enthalpy) Recovery: Deep Selection, the main differences are recovery efficiency, first cost, footprint, and how the air streams are handled. A plate exchanger keeps the streams fully separate and is simple, while a rotary wheel can reach higher recovery but allows a small carryover of moisture and a trace of exhaust into the supply. Air-to-water systems shift energy into a water loop instead of directly into the supply air, which suits buildings with a hydronic heating or cooling network.
Efficiency and Cost
Plate units typically recover 50 to 65 percent of sensible heat at modest cost and with low maintenance. Rotary wheels reach 70 to 85 percent including latent recovery, at a higher price and with moving parts. Air-to-water versions trade some efficiency for flexibility in where the energy is used. The best value depends on energy prices, run hours, and whether humidity control is part of the requirement.
Which to Choose
Choose a plate exchanger for clean, cost-sensitive duties; a rotary wheel when maximum recovery or latent heat matters; and an air-to-water system when the recovered energy must serve another loop. Always size from measured airflow and temperature data rather than nameplate guesses, because oversizing wastes money and undersizing limits savings.
Frequently Asked Questions
Is higher recovery always better? Not always; beyond a point the extra cost outweighs the marginal energy saved. Do rotating parts need service? Yes, the wheel seal and drive should be checked periodically.