Essentials

Since early in its involvement with the roofing industry, the spray polyurethane foam (SPF) industry has been active within the U.S. standards community. The current ASTM International standard, ASTM C1029, "Standard Specification for Spray-Applied Rigid Cellular Polyurethane Thermal Insulation," covers the types and physical properties of SPF intended for use as thermal insulation. SPF materials categorized within ASTM C1029 are used for multiple types of SPF products, including roofing materials, wall insulation and storage-tanker insulation.

The standard's physical properties are based on foams using chlorofluorocarbon (CFC-11) as a blowing agent. These foams were phased out in 1993. The current blowing agent is hydrochlorofluorocarbon (HCFC-141b), which will be phased out Jan. 1, 2003. A new blowing agent will be used for the next generation of SPF-based roof systems.

However, the SPF currently used in roofing applications does not meet ASTM C1029 requirements. The SPF industry is taking a two-pronged approach to ensure current SPF-based roof system materials are within the parameters of ASTM specifications by revising the minimum properties within ASTM C1029 and developing a material standard for SPF specifically used for roof systems.

The approach

Specifically, within ASTM C1029, dimensional stability values and R-values are being revised so they represent the materials currently being used. The current products then would meet ASTM C1029 requirements. ASTM C1029 requires a minimum R-value of 6.2 and maximum volumetric dimensional stability of 6 percent. The SPF industry seeks a minimum R-value of 6.0 and maximum dimensional stability value of 15 percent.

A proposed new standard currently titled "Standard Specification for Spray-Applied Polyurethane Foam Used for Roofing Applications" is going through the ASTM standard development process. A first draft has been developed, and more work is expected during at least the next couple of years before the draft will become a published standard.

Complications

Current SPF products must meet ASTM C1029 because all but one model building code requires that SPF used in roofing applications meet ASTM C1029 requirements. The BOCA National Building Code/1999, the Standard Building Code 1999 Edition, International Building Code 2000 Edition and International Residential Code 2000 Edition specifically reference ASTM C1029.

The Uniform Building Code (UBC) does not explicitly reference ASTM C1029. However, the International Conference of Building Officials (ICBO), which publishes UBC, has a process for accepting materials not referenced in the code; ICBO requires an evaluation report be submitted to a code official on a job-by-job basis. The report provides information describing materials used and proper preparations and applications for a roof system. In addition, evaluation reports reference acceptance criteria that provide evidence of appropriate physical properties. The current ICBO acceptance criteria for SPF is AC 12, "Acceptance Criteria for Foam Plastic Insulation." A revised AC 12 will be issued January 2003. The new version should account for the physical properties obtained with the new blowing-agent foams.

Solutions

Revising ASTM C1029, developing a roofing-specific standard and the upcoming evaluation report should address the building code noncompliance issue. In addition, the SPF industry is in the middle of a research project that should establish the physical properties of new blowing-agent foams. SPF-based roof systems manufactured with different blowing agents have been installed on commercial buildings. Samples of these buildings' roof systems are being evaluated to determine the new foam's physical properties. The physical property values from this research will be used to determine physical properties for the upcoming standard for SPF specifically used in roofing applications. For more information, see "The blowing-agent phaseout," January 2001 issue, page 22.

Some SPF manufacturers have taken the initiative to obtain evaluation reports for their products, which allows building officials to accept these products on a job-by-job basis. If you are involved with installing SPF-based roof systems, I encourage you to work closely with SPF manufacturers to ensure building code compliance.

James R. Kirby is an NRCA senior director of technical services.