Spray Foam-Thermal and Ignition Barriers

What is a thermal barrier? A thermal barrier is a material placed between spray foam insulation and the interior space of a building (in regard to the use of spray foam insulation with standard wall and roofline assemblies). The purpose of a thermal barrier is to delay the rate at which an uncontrolled fire increases the temperature of the spray foam insulation. The thermal barrier acts to prevent the foam insulation from becoming involved in the fire and to increase the amount of time available toward evacuating a building and fire fighting procedures. The IRC prescribes 1/2 inch thick drywall/gypsum board as a model thermal barrier. The protective properties of 1/2 inch thick drywall sets the standard for all other thermal barriers, which must meet or exceed the 1/2 drywall's values when tested in fire situations.        

What is an ignition barrier? Ignition barriers serve their role in open attics and crawlspaces containing spray foam insulation. Ignition barriers are a second defense against the start and spread of fire in these open spaces, and are applied directly against the spray foam insulation. Some examples of materials the IRC term as prescriptive ignition barriers are 1/4 inch thick wood structural panels, 3/8 inch gypsum board, and 3/8 inch particle board. Performance based ignition barriers are subject to testing standards under the AC377 Appendix X standards.  

When spray foam insulation is installed in a building the foam insulation is required to be protected by an approved thermal barrier. New residential construction will almost always "check" this requirement with the use of drywall/gypsum board throughout the home. This being said, there are instances where additional thermal and ignition barriers will still be required in a home. Though not always limited to, a majority of these discrepancies will derive from the home's attic space. Whether or not a thermal or ignition barrier is required in an attic relies on a number of factors. 

Is the spray foam product compliant with AC377 Appendix X testing? The testing involved with this method verifies that the spray foam insulation product remains within the acceptable predetermined burn rates during a fire. With these improved burning characteristics, Appendix X spray foam insulation may be used in an attic without a directly applied thermal or ignition barrier. If the spray foam insulation is not classified as an Appendix X product, an additional ignition barrier will still be required in all accessible attic areas. We install Appendix X classified spray foam insulation for our customers as a safe and economical option.   

Will any of the attic space be used for storage? Appendix X spray foam insulation will require an additional thermal barrier if space in the attic is to be used for storage. Local code officials may consider additional decking and fully framed entries as ques toward this, even if there is no intent to utilize the area for such. It is also advised to take into account how easily accessible an area of attic space is. Standard scuttle holes generally serve only as access to mechanical equipment in the attic, and suggest as much. A staircase leading into a fully decked attic area strongly suggest an intent to use the area for storage. Another example includes an unfinished bonus room, left to take drywall at a later date. In this instance, the exposed spray foam insulation will still require a thermal barrier. Installing a prescribed rigid thermal or ignition barrier will often times requires a substantial amount of time and labor, especially when installing in attic spaces and other confined areas. Our spray applied thermal and ignition barriers often times require much less time and effort to install. This can lead to reducing costs and a sooner date of completion. If in the case the thermal or ignition barrier is the finished product, they can be painted with any desired color.   


Does my metal building require a thermal barrier? If spray foam insulation is installed in your metal building, a thermal barrier is still required per code mandates.

It is important to discuss the features of your home or building and determine whether or not thermal or ignition barriers are necessary. Foregoing this step in the process raises the potential risk for liabilities and could affect the safety of individuals occupying the area. Each project will require its own unique plan, and we assist our customers with choosing the methods that best fit their intended uses and interests.