Building Code Compliance With SPF Insulation

Fire safety testing and compliance has been a consistent part of building codes for decades for good reason. When it comes to SPF, it is important to recognize that the building code treats all foam plastics the same. Hence polyurethane, polyisocyanurates, extruded polystyrene all fall under the same code sections even though the fire characteristics of these products are vastly different. For example, extruded polystyrene (used in some foam board or coffee cups) will melt and drip when it burns since it is a thermoform material that will create a flame. By contrast, polyurethane chars and flakes when exposed to fire, meaning that it will burn but will not propagate a flame.

Regardless of these actual variations in foam plastics, the International Construction Codes don't differentiate one foam plastic from another. Instead, code provisions require that all foam plastic must be separated from the interior of buildings by a 15 minute thermal barrier. Specific requirements for these provisions for commercial buildings are found in section 2603 of the International Building Code and for residences in Section 316 of the International Residential Code. As a practical matter, meeting these fire separation provisions usually means providing a half-inch thick layer of gypsum board over foam plastic used in wall, roof, or ceiling framing.

Building codes typically require wall assemblies with 15-minute fire separations between any type of plastic foam product and the interior of the building. Image courtesy of Demilec (USA) LLC

 

It should be noted that there are some exceptions to this thermal barrier requirement including applications in attics and crawlspaces. In attics and crawlspaces an ignition barrier is called for (instead of the 15 minute barrier) over the inside face of the foam, specifically 3/8-inch gypsum, ¼-inch plywood, ¼-inch hardboard and a few other board products. However, this type of application would likely be very difficult and expensive in most buildings.

Luckily the code also allows for specific approvals, based on large scale fire tests related to the actual end use configuration of a product. This is performance based compliance as opposed to prescriptive based compliance for fire safety. Essentially, if a product can be tested to demonstrate that it will outperform a code compliant methodology then it can be designated as code compliant. In this regard there are a number of important tests that can be referenced or required as part of a product specification. For attics and crawlspaces that use SPF insulation a modified NFPA 286 (AC 377) test can be performed in addition to ASTM E970. For interior finish testing, NFPA 286 and UL 1715 would be applicable to determine that the interior is appropriately protected. Exterior walls in buildings of Type I to IV would rely on NFPA 285 as the preferred test. Finally, for testing a full fire rated assembly that uses SPF insulation, ASTM E119 could be performed. It is important to specify the appropriate testing and request submittals documenting compliance as appropriate to a particular building application. The design of the full assembly is important in order to assure not only code compliance, but protection of the health, safety, and welfare of the occupants, therefore it is crucial to always ask the manufacturer for proof of compliance with these fire safety standards and tests.