Step 1 - Define the Duty

• Supply and exhaust airflow (they should be close to balanced for recovery to work)
• Outdoor winter and summer design temperatures
• Indoor setpoint and allowable supply-air temperature

Step 2 - Pick the Technology

• Dry climate, no humidity need - sensible plate core
• Humid climate, moisture control - enthalpy wheel or membrane plate
• Long life, no moving parts - heat pipe
• Very high effectiveness needed - rotary wheel

Step 3 - Check the Limits

• Pressure drop versus fan power budget
• Frost risk below about -2 C exhaust dewpoint
• Space available for the core or wheel

Step 4 - Verify

Confirm the selection against an EN 308 or AHRI 1060 rating at your actual operating point, not the headline number. A sizing tool that shows the curve is worth more than a single percentage.