The Historical Focus on Fire Standards for Low Density Foam Sealants

Posted on 10/2/2014 3:18:23 PM By Bob Braun

In my last several posts, I: featured the many facets of sealants and adhesives that have reduced density; discussed the increased value of reduced density sealants and adhesives; and reviewed the primary advantages and disadvantages for these products and provided some application examples for the same. In this post, I discuss the reasons for the increased focus on the fire issues for some of these sealants and why some concerns have surfaced.  In addition, I review how the industry has addressed these issues so far.

For example, if you review the label for most aerosol foam sealants, you will see a UL Classification for UL723 (similar to ASTM E84).  Most are familiar that this test is used to establish the surface burning characteristics for many building materials.  Initially, it was to only fire related performance test used in this industry.  Currently, the ASTM Specification C1620 for foam sealants requires product testing at a coverage rate of 12.5% using ¾ inch diameter beads.  The spec requirement is < 25 Flame Spread at this coverage.  The label may also reference to the use of other standards mentioned below.

To begin, when foamed sealants first hit the market, circa 1970, they were viewed simply as sealants and by the late 1980's confusion arose as to whether they were not also plastic foam.  This issue has been primarily restricted to sealants because they were visually observable in the final building construction and foamed adhesives are normally compressed to the profile and density of a non-foamed adhesive in many applications.  Those familiar with the fire issues related to plastic foam insulation, of the many types available, easily see how concerns arose over foamed sealants.  Building codes have required that plastic foam insulation must be covered by a 15 minute thermal barrier that protects the inhabited space of a building from the spread of fire ever since several major fires involving exposed foam insulation were reported now over 50 years ago.  Although these fires occurred when entire wall or ceiling areas were covered by foam plastic insulation, it eventually came to the point that any amount of exposed plastic foam was required to pass one or more standardized tests in order avoid the thermal barrier requirement of the building codes.

Initially, it was thought by many in the industry that foam sealants should be exempted, since the exposed plastic foam surface was very small, but there were cases where foam sealants might be used in an excessive amount or inappropriately at full coverage.  So, eventually manufactures began evaluating the foam sealants in tests like the NFPA 286 room-corner test at various application rates.  The independent test lab report was then was used to obtain an ICC-ES Evaluation Report that allowed exceptions to the thermal barrier requirement when the sealant was used at or below the tested application rate.

Similar requirements exist for other plastic foam products as well.

For many uses of the foam sealant, the thermal barrier requirement was not an issue since the product was used within the wall, floor, or ceiling cavity and therefore not exposed anyways.  But for some useful applications, the foam sealant (like elastomeric sealants) was exposed to the inhabited space.  This included penetrations through walls, ceilings, and floors for pipe and duct routing.  See photo examples below.


This was not the only fire related issue the industry had to deal with.  At the end of the 1980's, questions even arose related to the use of foam sealant within wall cavities. Foam sealant had been used for many years to seal the annular space around cable, pipe, and duct penetrations passing through the top and bottom plate within the wall cavity of wood or metal frame construction.  The building codes (for many years) had incorporated language referencing the term “fireblocking” in connection with insuring that the continuity of these plates were maintained around such penetrations.  The code language mandated the use of equivalent or non-combustible materials for sealing these type of penetrations.  The reality was that these air leakage paths were often not sealed well due to the code prescribed recommendations until the foam sealant emerged as a fast and efficient solution.  Because the wall cavity connects the conditioned living space to the unconditioned attic or crawlspace/basement through various interior and exterior wall penetrations for various utilities, such as electric outlet and switch boxes, sealing top and bottom plates is a large energy saver.  Example photos are shown below.


Initially, to counter this issue, foam sealant proponents argued that since this application was applied to combustible construction, the code language should be revised.  However, that was not to be without once again demonstrating through testing that foam sealant could perform adequately to other code prescribed materials in a modified ASTM E814 fire assembly test (no hose stream test is performed).  This test is shown below with steel pipes passing through 1.5 inch thick lumber to simulate the bottom plate of the wall cavity.  The chamber below is a furnace that produces fire condition temperatures.

astm e 814

In my next post, I will show and discuss examples of the use of inappropriate types of sealants and adhesives based on the application requirements.  

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