A.Paul Fisette responds: As your own experience suggests, unvented crawlspaces pose no real problems — as long as there isn’t excessive moisture. In your case, you have provided a continuous sealed vapor barrier across the crawlspace floor and, I would guess, proper foundation drainage on the outside.
Nevertheless, you still have two code hoops to jump through: the Model Energy Code and the BOCA code. Unfortunately, in this case, the two codes don’t necessarily jibe.
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