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is a material classified as "air-impermeable" if the tested air permeance is less than 0.02 Us-m2 at 75 Pa pressure differential. ➢ Air Impermeable Insulation — Insulation material having an air permeance less than 0.02 Us-m2 at 75 Pa pressure differential when tested in accordance with ASTM E 283 or ASTM E 2178. ➢ Ignition Barrier- A material, which limits combustive damage, burning and charring, to the immediate area of fire exposure when tested in accordance with NFPA 286 or UL 1715 as modified by Appendix A or Appendix X of ICC-ES evaluation criteria AC377. Prescriptive ignition barriers specified in the Building Code are: • 1 '/2" thick mineral fiber insulation • %4" thick wood structural panels (plywood or OSB) • %4" thick particleboard or hardboard � 3/8" thick gypsum board • Corrosion resistant steel having a base metal thickness of 0.016" A number of SPFI products are tested under Special Approval exposed or with intumescent coatings as an alternative to the code prescribed ignition barriers. ➢ Thermal Barrier—A material that will limit the average temperature rise on the unexposed surface to no more than 250° F after 15 minutes of fire exposure complying with the ASTM E 119 standard time temperature curve. Based on testing in accordance with FM 4880, UL 1040, NFPA 286, or UL 1715, the thermal barrier material must remain in place for 15 minutes. According to Section 2603.4 of the Building Code, '/2" gypsum wallboard qualifies as a prescriptive solution for a thermal barrier. ➢ Crawl Space— Unfinished space enclosed by foundation walls between the bottom of the floor joists of the lowest supported floor and the ground surface below. ➢ Closed Crawl Space—A foundation without wall gravity vents that uses air sealed walls, ground and foundation moisture control, and mechanical drying potential to control crawl space moisture. Insulation may be located at the supported floor level or at the exterior walls of the crawl space. Conditioned crawl spaces, defined below, are a special case of closed crawl spaces. Not all closed crawl spaces are conditioned. The crawl space is not considered to be conditioned when an exhaust fan system, separate from the building interior HVAC system and designed to exhaust at a minimum rate of 1 cfm per 50 square feet of crawl space area, is installed in the crawl space. Ventilation exhaust fans must operate whenever the relative humidity within the crawl space exceeds 60%. ➢ Conditioned Crawl Space—A foundation without wall gravity vents that encloses an intentionally heated or cooled space below the lowest supported floor. Insulation is located at the exterior walls of the crawl space. "Intentionally heated or cooled" means air is both supplied to the crawl space and returned from the crawl space by the equipment serving the building at a minimum exhaust rate of 0.02 cfm per square foot of crawl space floor area on a horizontal projection. Closed crawl spaces become plenums when the crawl space is used as a means to distribute supply air from the equipment serving the building to other spaces in the building or as a means to return air from other spaces in the building to equipment serving the building. File Number: 017-10 Spray Polyurethane Foam Insulation — Building Code Page 5 of 31