CodeMandatory
Insulation flame-spread index
IRC R302.10Description
Exposed insulation in attics and crawl spaces must have a flame-spread index ≤25 and smoke-developed ≤450, OR be covered with an approved barrier.
Why this exists
Loose insulation can ignite from a single spark; either the material is non-combustible or it's protected.
Categories
Life safety
Source
ICCno manifest entry
International Residential Code (2024)
Section: R302.10
Published 2024-01-01 · last verified 2026-05-09
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Garage / dwelling fire separation · IRC R302.6
- Habitable space minimum ceiling height · IRC R305.1
- Egress window net opening dimensions · IRC R310.2
- Stair riser, tread, and headroom · IRC R311.7
- Smoke alarms required throughout dwelling · IRC R314
Last reviewed 2026-05-09.