Cite authoritative, freely available standards and guidance before specifying a crawlspace encapsulation scope (vapor barrier spec, ventilation approach)

Steps

1. Cite IRC Section R408.2 (unvented crawl space provisions, present since the 2012 IRC cycle) for the baseline code requirement that exposed earth be covered with a continuous ground vapor retarder meeting ASTM E1745 with permeance below 0.01 perms
2. Cite DOE Building America's BSC Information Sheet 512 ('Crawlspace Insulation for All Climates,' prepared by Building Science Corporation) for insulation placement and detailing guidance beyond the bare code minimum
3. Cite EPA's basement/crawlspace moisture guidance (recommending indoor relative humidity kept below 60%, ideally 30-50%) as the performance target the encapsulation system should achieve
4. Reference ENERGY STAR's 'Basement & Crawlspace Air Sealing and Insulating' project guide (energystar.gov) for a homeowner-facing summary of the same principles
5. Verify which IRC edition/amendments the local jurisdiction has adopted before finalizing the vapor-barrier thickness and ventilation-exception details in the spec