Originally Posted by
Myk Rian
John;
Since answering your question with a reference to Residential code 309.1.1, I did some additional searching on the subject. I was led to a forum where members are the actual building code inspectors. They provided me with some additional, important information.
#1 on that list was "Check with your local building department". Even though R309.1.1 is an international building code adopted in the US, there is always the possibility that your local code may be different, or non-existent.
#2 "Check with your insurance carrier", for obvious reasons.
Those persons also mentioned that approved fire dampers in the supply and return ducts may be accepted where the walls are penetrated. Again, local codes prevail.
Now, there is another matter. That is one they called the "Energy codes", and pertains to insulation, and other matters. Those codes are, according to them, a bit tougher than building codes. Again, ask at your local building department.