Spray Foam Insulation & Fire Code: 2 Critical Safety Points


All foam products – with the exception of Appendix X rated spray foam – require one of the two following options to be in place to meet fire code in a residential attic.


A 15-minute thermal barrier between the spray foam insulation and the living area.


Apply spark-resistant paint to the surface of the foam.


Contrary to popular belief, a 1/2″ layer of drywall on the ceiling between the attic and the living area IS NOT a 15-minute thermal barrier.

Drywall is a component of a 15-minute thermal barrier but it is not the thermal barrier itself.

Common Thermal Barrier Mistake

You may have heard from a contractor or read online that a thermal barrier is a 1/2″ layer of drywall.  This is a common misunderstanding.  In a residential attic a 1/2″ layer of drywall is a component of the thermal barrier but is not the thermal barrier itself.

15-Minute Thermal Barrier Requirements

Component15-Min Requirement
drywall1/2″ drywall
attic accessinstall fire rated access hatch
lightinginstall fire-rated lighting cover
sealed with fire-rated foam
electrical boxesseal with fire-rated foam
wire penetrationsseal with fire-rated foam
ducts & pipesseal with fire-rated foam
open soffitscover with 1/2″ drywall &
seal with fire-rated foam
gaps & cracksseal with fire-rated foam

The Fire Code & Spray Foam Insulation Is Confusing

Different foam insulation products have a range of requirements that vary by type of construction. Furthermore, how you plan to use the insulated space can affect the fire code requirements.

Additionally, a change in the depth of your foam can modify the fire code requirements even if everything else about the project is unchanged.

On top of all that, there is no shortage of confusing and contradictory information available to you online.

However, in the Phoenix area, the fire code as it relates to spray foam insulation in residential attics can be reduced to the following three statements:

Statement #1

If you install an Appendix X rated spray foam insulation, then you do not need a 15-minute thermal barrier or a spark resistant coating.

Statement #2

If you do not install an Appendix X rated  product, then a spark resistant coating is required unless you have a 15-minute thermal barrier.

Statement #3

If you do not install an Appendix X rated foam insulation and do not apply a spark resistant coating, then you are required to have a 15-minute thermal barrier between the spray foam and the living area.

Final Words

Keep the two points and three statements above in your mind as you research spray foam insulation. As a result, you’ll find it much easier to understand which products are the best for your particular application.

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