Ignition Barriers are required in attics or crawl spaces where entry to these areas is only for servicing of utilities. This can mean access to the HVAC unit for servicing or repairs, access to the water heater, electrical systems, alarm systems, in-ceiling speakers, etc. You get the idea. These attics and crawl spaces may NOT contain storage of any kind. Unfortunately, Code does not describe what ‘storage’ means.
Ignition barriers are designed to be installed to provide a ~5 minutes rating to the area, for egress. This test to ensure compliance of the material is referred to as the Appendix X Test. Ignition barriers include DC315 (applied at prescriptive thicknesses – refer here: https://painttoprotect.com/matrix/) as well as several prescriptive/equivalent items such as:
3/8-inch gypsum board (prescriptive)
1 1⁄2-inch-thick mineral fiber insulation
1/4-inch-thick wood structural panels
1/4-inch hardboard
For a more comprehensive list, please refer to your local Building Code.
Conversely, Thermal Barriers are required in attics or crawl spaces where storage IS permitted or expected to occur. Thermal Barriersare thicker or more robust than Ignition Barriers to handle the more stringent test of 15-minutes to achieve NFPA286. Again, use of DC315 intumescent coating may be used to cover the spray foam at a tested thickness (refer to the DC315 Matrix for coating data: https://painttoprotect.com/matrix/. Like Ignition Barriers, Thermal Barriers include other prescriptive items such as:
1/2-inch gypsum board (prescriptive)
1 ½-inch-thick mineral fiber insulation
Spray applied cementitious material
Spray applied cellulose materials
For a more comprehensive list, please refer to your local Building Code.
Another consideration is access to the attic. Should there be a situation where the attic is accessed through a full-sized door (e.g. a walk-in attic) which is decked or partially decked – this would most likely need to be treated as a Thermal Barrier Attic. The assumption would be that the area is highly accessible and therefore more likely to contain ‘storage’. The same or similar argument could be made for a pull-down access attic. Again, it comes down to the intent use of the space.
When in doubt – err on the side of caution and take the conservative route and bid/suggest Thermal Barrier.
As always if you have any question on this or other similar topics, please be sure to ask a member of the IFTI Team!