 EPA’s “Where You Live” for more information.
Section R408.1 Ventilation. Ventilated crawlspaces should have at least 1 ft2 of vent opening for each 150 ft2 of floor area, unless the ground is covered with a Class 1 vapor retarder, then 1 ft2 of vent area is required for each 1,500 ft2 of floor area.
Section R408.2 Openings for under-floor ventilation. Ventilated crawlspaces should have at least 1 ft2 of vent opening for each 150 ft2 of crawlspace floor area, unless the ground is covered with a Class 1 vapor retarder, then the total area of ventilation openings should be equal to 1/1,500 of crawlspace floor area.
Section R408.3 Unvented crawl space. Ventilation openings are not required in the crawlspace if the exposed earth is covered with a continuous Class I vapor retarder with seams that are overlapped by 6 inches and sealed or taped and with the edges fastened and sealed to the foundation walls at least 6 inches above the ground level.*
*Due to copyright restrictions, exact code text is not provided. For specific code text, refer to the applicable code.
Foundation Capillary Break over Aggregate = Foundation Floor Water Barrier