Are the panels fire resistant or do they have to be covered

InSoFast continuous insulation panels carry a Class A fire rating, but building codes require interior installations to be covered with an approved 15-minute thermal barrier, such as half-inch drywall, before occupancy.

Model building codes across the United States, Canada, and Mexico treat rigid foam plastics as combustible materials requiring thermal protection. Under 2024 International Residential Code (IRC) Section R316.4, exposed foam plastics in habitable living areas present smoke and flame propagation risks during a structure fire if left unprotected.

If you only do one thing: Fasten 1/2-inch gypsum drywall directly into the embedded panel studs using 1-5/8-inch drywall screws to meet the mandatory 15-minute thermal barrier code standard.

• Fire classification: InSoFast closed-cell expanded polystyrene (EPS) foam panels are manufactured with flame-retardant additives to achieve an ASTM E84 Class A fire rating with a flame spread index of 25 or less.
• Thermal barrier mandate: IRC Section R316 and IBC Section 2603 require interior foam insulation to be separated from occupied living space by an approved 15-minute thermal barrier, standardly met by 1/2-inch (12.7 mm) gypsum wallboard.
• Built-in fastening strips: Injection-molded polypropylene studs spaced 16 inches on center provide continuous framing that receives drywall screws directly, eliminating the need for separate wood furring strips or metal studs.
• Fastener specifications: Attach interior wallboard using 1-5/8-inch coarse-thread drywall screws driven into the panel's recessed stud lines at 12-inch vertical intervals.
• Exterior cladding integration: For above-grade exterior installations, panels must be covered by code-compliant weather-resistant claddings such as fiber cement siding, engineered wood, vinyl, or masonry veneers.
• Attic and crawlspace exceptions: In limited-access utility spaces without storage or fuel-fired appliances, local building authorities may allow an approved ignition barrier (such as 3/8-inch drywall or 1/4-inch wood structural panels) in place of a full 15-minute thermal barrier.

• Watch out for: Leaving foam panels exposed in occupied basements, living areas, or shipping container homes, which violates standard residential fire safety codes and fails municipal building inspections.
• Watch out for: Fastening combustible thin wood paneling, shiplap, or decorative planking directly over the foam without first installing an approved 1/2-inch gypsum underlayment.
• Watch out for: Missing the embedded polypropylene studs during drywall installation, which compromises the structural attachment of the thermal barrier under load.

Verify your local municipality's specific thermal barrier requirements for basement renovations or container conversions, then specify 1/2-inch drywall over your InSoFast panel layout.