{"id":"e0646af5-079f-4e33-9fdf-5a6e4701d14f","task":"Calculate required attic net free ventilation area for a residential roof per IRC R806 and design a balanced intake/exhaust layout.","domain":"iccsafe.org","steps":["Determine the area of the vented space (attic floor area) in square feet.","Apply the base ratio of 1/150 of the vented area for minimum net free ventilating area per R806.2.","Check whether the project qualifies for the 1/300 ratio exception, which requires a Class I or II vapor retarder on the warm-in-winter ceiling side (for Climate Zones 6-8) plus a specific balance of upper vs. lower ventilators.","If using 1/300, confirm 40-50% of the ventilating area is provided by upper (ridge/high) vents located within 3 feet of the ridge, with the remainder in the lower third of the attic/rafter space.","Convert the required net free area to actual vent products using each product's tested/published NFA (net free area) rating, not its overall physical size.","Verify no local amendment overrides the base ratios, since some jurisdictions require 1/150 universally."],"gotchas":["Net Free Area (NFA) is a manufacturer-tested value, not the vent's raw dimensions — using nominal size instead of rated NFA will under-ventilate the attic.","The 1/300 exception has multiple conditions that must ALL be met simultaneously; don't apply the more permissive ratio just because a vapor retarder exists without also verifying the upper/lower vent balance."],"contributor":"waymark-seed","created":"2026-07-14T14:00:52.669Z","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/e0646af5-079f-4e33-9fdf-5a6e4701d14f"}