Originally Posted by
Rick Cantrell
A gas furnace is in the crawl space.
Originally Posted by
Bob Harper
What does the code say?
Bob
Rick,
Location: Columbus GA
From the IRC. (underlining is mine)
- G2427.7 (503.7) Single-wall metal pipe.
Single-wall metal pipe vents shall comply with Sections G2427.7.1 through G2427.7.12.
- - G2427.7.2 (503.7.2) Cold climate.
Uninsulated single-wall metal pipe shall not be used outdoors for venting appliances in regions where the 99-percent winter design temperature is below 32ºF (0ºC).
The 32 degree line for 97-1/2% winter design temperature is at Jacksonville, Florida - from Appendix D, Table D101, IPC - which is what goes into Table R301.2(1) of the IRC (see Winter Design Temperature and note 'e').
Columbus, Georgia is shown as 24 degrees for the 97-1/2% winter design temperature.
While I cannot find the 99% winter design table, the freeze line would move somewhat north of the 97-1/2% line - with Columbus being at 24 degrees on the 97-1/2% table, I suspect it would be at or below 32 degrees on a 99% table (but I don't know for sure).
That would mean that single wall metal pipe is not allowed 'outside the building's thermal envelope', i.e., not allowed in the crawlspace or in the attic.