David,

That would be a start. Other factors can contribute. A filthy system, filter, blower and evaporator coil as well as some registers being closed, will not draw as much air as a clean system. You would also want to consider the ways a home can be depressurized - exhaust fans and fireplaces.

Certainly the method you present is valid but I wouldn't let it be the last word.

__________________
Eric Barker
Moraine Woods Consulting, Inc.
Barrington, IL