Crawl spaces shall be ventilated by openings through the perimeter wall connecting to the exterior of the foundation. Required vents shall have a combined net free area not less than 1 square inch (0.000645 m2) per 1 square foot (0.0929 m2) of crawl space, and shall conform to the following conditions:
- Openings shall be distributed uniformly around the outside walls of the crawl space.
- Vents shall be fitted with corrosion and decay-resistant wire mesh or grilles with openings not less than 1/4 inch (6 mm) nor more than 1/2 inch (12.7 mm) in size. Vents shall not be fitted with operable louvers, dampers, or other closure mechanisms.
- Plumbing located in a ventilated crawlspace shall be protected from freezing with insulation and/or heat tape.