Air Infiltration Rate

[smeismer]

Section 304 of the IFGC describes a couple of options for combustion air based on air infiltration rate. Obviously this is not the air infiltration rate described in the IECC, as that relies on a 50 pascal pressure differential. The handbook suggests that typical rates would be from .35 to .60 air changes/hr, while the IECC expects something less than 7. As this is obviously not a suitable value for determining combustion air, it leaves the question, which neither the IFGC or the commentary answers. How is this measured? Is there an ASHRE standard that is not mentioned? Does the measurement require multiple wind conditions on the building? Any insight would be appreciated.