What are the minimum outdoor air damper leakage requirements in ASHRAE 90.1?

ASHRAE 90.1-2019 Section 6.4.3.4.3 requires outdoor air intake and exhaust dampers to have a maximum leakage rate of ≤3 CFM/ft² at 1 in. w.g. when tested per AMCA 511, effectively mandating AMCA Class 1A rated dampers. The standard also requires that outdoor air dampers be motorized, interlocked with the supply fan to close when the fan is off, and capable of modulating to meet minimum ventilation requirements during occupied mode. These requirements are particularly critical in cold climates (ASHRAE Climate Zones 4–8) where damper leakage represents a significant heating energy penalty and coil freeze risk during winter unoccupied periods.