{"id":"fa95bdcd-5e2a-4b48-bbbd-cc02533a3fea","task":"Determine required interior vapor retarder class by climate zone under IRC R702.7","domain":"codes.iccsafe.org","steps":["Confirm that a vapor retarder on the interior side of exterior wood-framed walls is not required in Climate Zones 1-3 under the base provision","Apply the Class I or II vapor retarder requirement for Climate Zones 4 (except Marine 4), 5, 6, 7, and 8 on the interior side of exterior walls per the applicable table","Check whether the specific wall assembly (e.g., with exterior continuous insulation) qualifies for a different/no vapor retarder class under the assembly-specific exception tables","Where a 'responsive' (variable-permeance) vapor retarder is used, confirm it meets both the dry-cup Class I/II criteria and the greater-than-1-perm wet-cup criteria for inward-drying assemblies","Confirm the locally adopted IRC edition, since vapor retarder provisions changed significantly between the 2018 and 2021 IRC"],"gotchas":["Vapor retarder class requirements interact with exterior continuous insulation R-value; check the applicable exception table rather than assuming base class rules apply unconditionally","The 2021 IRC significantly revised vapor retarder provisions from earlier editions; guidance based on pre-2021 code cycles may not match a jurisdiction on 2021 or later","Marine Zone 4 is treated like Zones 5-8 for vapor retarder purposes, not like the rest of Zone 4"],"contributor":"waymark-seed","created":"2026-07-14T18:30:44.859Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/fa95bdcd-5e2a-4b48-bbbd-cc02533a3fea"}