Code and Fire Test Requirements for Foam Plastic Insulation Used in Exterior Walls

By Jesse J. Beitel Hughes Associates Inc. and Bruce J. Spiewak, AIA, Consulting Architect, LLC

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proper example of through penetration firestopping
Here is an illustration of a multi-component wall system. Click here to see full-size version of this illustration.

The 2007 edition of ASHRAE 90.1 “Energy Standard for Buildings Except Low-Rise Residential Buildings,” as well as the 2006 and 2009 editions of ICC’s International Energy Conservation Code® have significantly increased the minimum required R-values for exterior walls in most of the United States. These increases can be addressed in several ways, but typically architects are meeting these requirements by use of “continuous insulation” (CI) on the exterior walls. CI is defined as “insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings.” 

One primary means of accomplishing CI is to install continuous insulation on the exterior side of steel studs that form the exterior walls. The illustration above provides a diagram of this general type of construction. Typical insulation materials are noncombustible mineral wool or combustible foam plastic insulation of various types. The types of foam plastic insulation can be but are not limited to extruded polystyrene foam, expanded polystyrene foam, polyisocyanurate foam or spray-applied polyurethane foam.

This article addresses the various code and fire test requirements for the use of foam plastic in exterior walls.

The International Building Code® (IBC) regulates most aspects of the construction of buildings including the exterior walls. Chapter 6 of the 2006 IBC and recently published 2009 IBC both require that exterior walls of Type I and Type II buildings be of noncombustible construction. There are some exceptions specifically listed in Section 603.1.  Section 603.1 (3) specifically states that foam plastic insulations are allowed to be used when the foam plastic insulation and the wall assembly meet the requirements of Chapter 26 of the IBC. This section of the Code specifically addresses the flammability requirements for combustible foam plastic insulation used in this application.

Compliance with §2603.5 is required when foam plastic is used in exterior walls of buildings of Type I, II, III, or IV construction of any height. Exterior walls of Type V construction and some one-story buildings are exempt from these requirements. Thus, almost all exterior walls that contain foam plastic insulation must meet the requirements of Section §2603.5.

 In general, the requirements of §2603.5 include:

  •  §2603.5.1 – This section requires that the installation of the foam plastic cannot reduce the fire-resistance rating of the wall assembly if it is required to have a fire-resistance rating. Test data per ASTM E119 (or UL 263) must be submitted to substantiate the rating.

  •  §2603.5.2 –  This section requires that the foam plastic insulation be separated from the interior of the building by a 15-minute thermal barrier, typically minimum ½ inch thick gypsum wallboard (either exterior sheathing or interior type).

  •  §2603.5.3 – This section requires that the potential heat of the foam plastic (btu/ft2), as determined by NFPA 259, cannot exceed that which has been successfully tested in accordance with NFPA 285.

  •  §2603.5.4 – The foam plastic shall have a flame-spread index of 25 or less and a smoke-developed index of 450 or less in accordance with ASTM E84 (or UL 723). There is an exception for certain prefabricated aluminum faced panels.

  •  §2603.5.5 – The wall assembly shall meet the requirements of NFPA 285 “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components.”

  •  §2603.5.6 – The foam plastic shall be labeled by an approved quality control agency.

  •  §2603.5.7 – The wall assembly shall not exhibit sustained flaming when tested via the NFPA 268 “Standard Test Method for Determining Ignitibility of Exterior Wall Assemblies Using a Radiant Heat Energy Source.” There are exceptions for assemblies protected by a variety of materials.

Out of all of the test requirements in §2603.5, the primary and most important fire test requirement for this application is NFPA 285 “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components.”

This fire test evaluates the vertical and lateral flame-propagation potential of wall systems that contain combustible components, typically foam plastic insulation. The common type of wall system evaluated is non-load-bearing, exterior curtain wall construction. This test exposes an exterior wall assembly to a “typical” fire scenario. The fire scenario is one in which a fire occurs inside a room, the fire vents through a window opening and the exterior wall is exposed both from the interior and to a flame plume exiting the window.

The test measures the following parameters:

  •  Vertical and lateral flame propagation over the exterior face of the wall assembly.

  •  Vertical flame propagation within the combustible core or within combustible components from one story to the next.

  •  Vertical flame propagation over the interior surface of the wall assembly from one story to the next.

  •  Lateral flame propagation from the compartment of fire origin to adjacent compartments or spaces.

During the 30-minute test, and for 10 minutes after shutting the gas flow off, these parameters are measured by visual observations and temperature measurements at locations on and within the wall assembly. While some fire propagation is allowed, the acceptance criteria limit fire propagation on and within the test wall assembly.

We'd like to emphasize several important points concerning the applicability and use of test results:

  •  This test is required for any wall system that contains foam plastic insulation. This means even brick veneer wall systems that contain foam plastic must be evaluated.

  •  This test is a test of an assembly. The complete wall assembly must be tested, and this includes wall system components such as combustible air/vapor/water resistive barriers.

  •  The results of the test apply only to the assembly tested. Substitution of materials such as one type of foam plastic for another type of foam plastic can provide different results. Someone knowledgeable with respect to the test and the materials in question must evaluate substitutions and such substitutions must be approved by the code official.

  •  Even though a specific component of the wall system has met the requirements of NFPA 285, if additional combustible components are added to the wall assembly, then the assembly may no longer meet NFPA 285. For example, if a Metal Composite Material (MCM) by itself is successfully tested via NFPA 285, and if a CI such as foam plastic is added to the system, the new combination of materials may not meet the Code and the NFPA 285 performance requirements. The new combination wall assembly must be tested.

In summary, with the increased use of CI, the NFPA 285 is an important test to evaluate and control the fire performance of foam plastic used in CI exterior walls such as that shown in the above illustration. The test applies to most exterior walls that contain foam plastic insulation in Types I, II, III and IV construction. The results of the test are limited to the assembly tested and if you change wall components or add new combustible materials, additional NFPA 285 testing may be required to verify that the wall assembly meets Code.

Since joining Hughes Associates, Inc., Jesse J. Beitel has provided consulting services on a wide range of flammability problems and issues that include technical studies, experimental programs and code representation. This work has included new product and materials design and development as well new applications for existing products and materials. His clients include manufacturers, trade associations, private industries and the U.S military. Beitel is a recognized expert on the flammability of materials, especially foam plastics used in construction. Contact Beitel at or 410-737-8677.

Since the founding of his West Haven, Connecticut-based code-consulting firm, Bruce J. Spiewak, AIA,  Consulting Architect, LLC, in 1982, Bruce J. Spiewak, AIA, has provided a unique technical consulting service to building owners, architects, engineers, code officials, builders, attorneys, institutions and others. His work has been exclusively in the area of code compliance and document review. Bruce has a special interest in the concept of building, fire safety and accessibility codes as an integral part of the design process. Contact Spiewak at, or (203) 931-9945 x 300.