fire performance in walls and ceilings

Foam Plastic Insulation and Building Codes

Sheathing and Wall Applications for Polyiso Insulation

The four model building codes - ICBO, ICC, SBCCI, and BOCA - include a specific section pertaining to the safe use of foam plastics in construction. For the typical wall application, there are three requirements:

? Flame spread of 75 or less on the foam core, as tested in accordance with ASTM E84

? Smoke development of 450 or less on the foam core, as tested in accordance with ASTM E84

? Use of a thermal barrier, such as ? inch (12.7 mm) gypsum board on the interior or occupied side of the building

Building codes have specific requirements for the use of foam insulation in special applications. For example, the need for a thermal barrier may be eliminated if the polyiso insulation product has performed successfully in a series of larger scale fire tests at accredited testing laboratories. Consult the polyiso insulation manufacturer for specific test results, code approvals, and recommended exposed applications.

Similarly, some polyiso insulation products have been formulated and tested for use in one and two-hour masonry and wood frame wall constructions. The standard test used to qualify time-rated assemblies is ASTM E119. Consult the polyiso insulation manufacturer and code authorities before installing the product in time-rated constructions.

Fire Tests Definitions

ASTM E84 (Standard Test Method for Surface Burning Characteristics of Building Materials) is a standard method to assess the spread of flame on the surface of a material. Often referred to as the "Tunnel Test", E84 involves installing a sample of material 20 inches wide and 25 feet long as the ceiling of a horizontal test chamber. The material is exposed to a 4-foot-long gas flame at one end of the tunnel for a period of 10 minutes. The rate of flame front progression on the material is compared to selected standards and calculations are made to produce a flame spread rating. Smoke from the fire in the tunnel is measured in the exhaust stack by using a light beam to evaluate smoke developed ratings. ASTM E84 also has a number of other designations, such as UL 723, NFPA 255, or ICBO 8-1.

Since ASTM E84 is a standard laboratory fire test on a single material, numerical ratings derived from E84 are not intended to reflect hazards presented by the test material under actual fire conditions.

ASTM E84: Polyiso Insulation vs. Polystyrene Insulation

Polyiso insulation, a thermoset material, stays intact during the fire exposure and successfully remains in place during the tunnel test, thereby meeting the necessary ratings dictated by building codes.

ASTM E119 (Standard Test Method for Fire Tests of Building Construction and Materials) is used to determine the fire resistance of a complete assembly. For example, a wall rating is measured by constructing a 10-foot by 10-foot section of total wall system: framing, cavity insulation, sheathing, siding, and gypsum wall board. The wall section is installed vertically on a gaas furnace, and the wall system is exposed to flame for the time period for which a rating is desired, i.e., one, two, three, or four hours. Failure points during time of fire exposure are as follows: flame penetration through the wall section, an unacceptable temperature increase on the unexposed side of the assembly, and structural failure or collapse of the assembly. Therefore, a one-hour fire resistance rating is taken to mean that a structure incorporating the tested wall construction will not collapse, nor transmit flame or a high temperature, while supporting a design load for at least one hour after a fire stared.

Ceiling constructions can also be tested horizontally in accordance with ASTM E119. The building code authorities usually designate the duration of ire resistance needed in a building. Factors affecting the duration of ire resistance include type of construction, occupancy designations, location of building, and insurance criteria.

ASTM E119 is also known as UL 263, NFPA 251, and UBC 7-1.