Originally Posted by
Ted Menelly
Crawl spaces are vented for a reason. Of course this discussion always gets nipped in the butt by many saying crawl spaces don't need ventilation.
Ted, There is quite a bit of info that supports the incorporation of the crawl space into the conditioned area and I strongly support that. We have a great deal of humidity here in the summer and when it enters a cool crawl it can create significant problems. Perhaps in other areas of the country it's not so much an issue.
Back to pulling combustion air from the crawl: You can do this with an attic provided that the attic itself is well ventilated. Crawl spaces on the other hand will often have vents to the exterior that can be closed. Not that I would necessarily expect this to actually make much of a difference, but by the book, it's a consideration to make note of.