Both are fire-protection coverings for spray foam, but they're not interchangeable - and the code asks for different ones in different spaces. Getting this right is part of a compliant install.
The difference
- Thermal barrier: the stronger requirement. It must slow the temperature rise to the foam for a set time (15 minutes is the classic benchmark). Standard half-inch drywall is the common thermal barrier. Required in occupied/living space.
- Ignition barrier: a lighter covering that resists flame spread, allowed in spaces people don't normally occupy - some attics and crawlspaces - where an approved intumescent coating can qualify.
Which applies where
Living areas, finished basements, garages tied to living space -> thermal barrier (usually drywall). Limited-access attics and crawlspaces -> often an ignition barrier coating, per the code and the product listing.
The takeaway
Exposed foam in a living space isn't finished - it needs its thermal barrier. A good installer builds that into the plan. See Alberta code.
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