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The IRC defines a basement as 'That portion of a building that is partly or completely below grade (see "Story above grade").

There is no 'definition' in the IRC of a crawlspace; however, Section R408 says 'the under-floor space between the bottom of the floor joists and the earth under any building (except space occupied by a basement) shall have ventilation openings....'

The 2006 NJ Energy code defines a basement wall as 'A wall 50 percent or more below grade enclosing conditioned space.'

While it states a crawlspace wall is 'The opaque portion of a wall that encloses a crawlspace and is partially or totally below grade.'

So, what is a crawlspace?

When does the area under the first floor turn from a crawlspace to a basement?

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....enclosing conditioned space.

To me conditioned space means heated or heated and cooled space. If that is true, then the "basement" without a heat supply would require ventilation openings. The IRC has an alternative though, which details a air circulation system in place of the otherwise required ventilation openings. Does the energy code have a definition for conditioned space?

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What's a crawlspace? Why, most of the time, a really, really short basement, of course.

Ventilating a crawlspace has nothing to do with it's depth or whether you consider it a "basement" or a "crawlspace" - the need for ventilation depends on local climate and whether or not the earth floor of the space is covered with a cap sheet or left uncovered and whether you intend to "condition" the crawlspace atmosphere.

We have some "crawl" spaces out here that are literally 15ft. deep below the floor joists. Sometimes, owners of these do consider them basements and they do try to use them that way by building storerooms and such in them. They still need to be ventilated unless they condition the air in them. On the other hand, I've inspected homes with 24-inch deep crawlspaces that had concrete floors and conditioned air that didn't need vents at all.

The problem with the way the codes are written is that the folks that write them have "construction" knowledge, "electrical" knowledge, "plumbing" knowledge, "HVAC" knowledge, etc., but they lack building science knowledge.



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