Air Leakage is a term used to describe the unintentional leakage & infiltration of air into or out of a structure, system, or item.
For example, the NFRC has an optional rating (AL) that manufacturers can elect to list on their labels for this. The lower the AL value, the less air will pass through the assembly.
Duct Leakage Testing measures the leakiness of the duct system which is returned in a CFMs and is converted into a percentage based on the square footage of the conditioned space.
A Blower Door is used to measure the leakiness of a structure and is also based on a CFM reading and converted into an ACH or ELR reading..
