Section 6.5.6.1/Exhaust Air Energy Recovery
ASHRAE 90.1 Section 6.5.6.1 requires energy recovery ventilation for systems exceeding outdoor air thresholds by climate zone.
Energy recovery is required when the supply fan airflow rate exceeds the thresholds in Table 6.5.6.1 based on the climate zone and the percent outdoor air at design conditions. For example, in climate zone 5 (Chicago, Denver), energy recovery is required for systems with 70% or more outdoor air at design airflow rates of 750 cfm or more, and for systems with less than 70% outdoor air at higher thresholds. The energy recovery device must have an enthalpy recovery ratio of at least 50% at design conditions. The requirement applies to both heating and cooling energy recovery based on the climate zone.
Why this section exists
Ventilation air represents a significant energy cost: outdoor air must be heated in winter and cooled/dehumidified in summer. Energy recovery devices (enthalpy wheels, plate heat exchangers, heat pipes) transfer energy between the exhaust air stream and the incoming outdoor air stream, recovering 50-80% of the energy that would otherwise be wasted. For buildings with high outdoor air requirements (hospitals, labs, restaurants), energy recovery can reduce HVAC energy consumption by 20-40%.
What plan reviewers look for
Plan reviewers check the mechanical drawings for energy recovery devices on systems exceeding the Table 6.5.6.1 thresholds. They verify the climate zone, supply airflow rate, and percent outdoor air to determine whether energy recovery is required. They check the energy recovery device's rated enthalpy recovery ratio (50% minimum). They verify the device is shown on the air handling unit schedule or the mechanical plan.