"For gut rehab projects, use radon-resistant construction for existing buildings, as per ASTME-2121 (see www.epa.gov/radon/pubs/mitstds.html)." change to "Gut-rehab projects should use the new residential construction guidance in EPA\'s Indoor airPLUS, or existing residential buildings language in ASTME-2121. Post-occupancy tests are strongly encouraged. See www.epa.gov/radon/pubs/mitstds.html."