Confirm IRC unvented crawlspace requirements before sealing a crawlspace instead of venting it

Steps

1. Confirm the jurisdiction has adopted IRC R408.3 (or a state equivalent) permitting unvented crawl spaces as an alternative to passive vents — not all jurisdictions adopt this section without amendment.
2. Ground cover: install a continuous Class I vapor retarder over exposed earth, lapping joints at least 6 in and sealing/taping them, extending the retarder at least 6 in up the stem wall and attaching/sealing it there.
3. Provide one of the code's required mechanical conditioning options instead of relying on the vapor retarder alone: continuously operated exhaust ventilation sized to the crawlspace floor area, a conditioned-air supply/return pathway, or a dehumidification system sized to the code's moisture-removal rate.
4. Check for local amendments layering on additional conditions (termite inspection clearance, combustion-air requirements for gas appliances) beyond the base IRC text.
5. Document the completed condition (photos of retarder laps and stem-wall attachment) before the crawlspace is closed, since it becomes a concealed condition that's hard to re-inspect later.