Originally Posted by
Gunnar Alquist
But the problem that I had was this note in the Code Check (IRC edition) book that indicated both vents could not go into the crawlspace area even though I could not find the reference in the IRC.
Gunnar,
Nothing in the IRC or the Commentary to the IRC prohibits *both* openings from going to the crawlspace.
This is the code and part of the commentary, which lumps crawlspaces and attics into the same "allowed" category.
G2407.6 (304.6) Outdoor combustion air. Outdoor combustion air shall be provided through opening(s) to the outdoors in accordance with Section G2407.6.1 or G2407.6.2. The minimum dimension of air openings shall not be less than 3 inches (76 mm).
Commentary (underlining is mine)
- This section provides two methods for providing combustion air from the outdoors: the traditional method by means of two direct openings or ducts to the outdoors and a newer method by means of one opening or duct to the outdoors.
- Openings to spaces that are naturally ventilated with outdoor air, such as attic or crawl spaces, are considered as an acceptable alternative to a direct connection to the outside. Attic and crawl spaces can be acceptable sources of combustion air only where such spaces are provided with adequate natural ventilation openings directly to the outdoors. Attic and crawl spaces ventilated by mechanical means are not an acceptable source of combustion air.