Today I want to talk about thermal barriers.
In accordance with the building code, both the IRC and the IBC, all foam plastic insulation must be separated from the interior of the building by a 15-minute thermal barrier.
The code prescribed thermal barriers are ½ inch gypsum board or 23/32 wood structural panel.
The thermal barrier code section goes on to say that you can qualify other materials as a thermal barrier if they pass a specific test, NFPA 275.
The products that have passed the standalone thermal barrier test are materials such as Monokote 3306, a spray applied cementitious material, and then there are a couple of cellulose-based materials that are spray applied as well, like K13.
These are standalone thermal barriers.
Do not confuse this with an intumescent coating, let’s be clear about this, intumescent coatings are not thermal barriers; no paint product passes the thermal barrier test on a standalone basis.
When intumescent coatings are used over spray foam, they pass a systems test as an interior finish in accordance with IBC 803.2, so that specific foam and that specific coating can be used in lieu of a thermal barrier. It basically omits the thermal barrier requirement by being an interior finish system that meets the interior finish acceptance criteria of the building code.
This is a different test than NFPA 275, so the coatings are not standalone thermal barriers, and this is important because you can’t take one coating and put it over any foam out there, it has to be a coating that is tested over a specific foam.
The tests with intumescent coatings omit the thermal barrier requirement by passing an NFPA 286 test in accordance with the acceptance criteria of IBC 803.2, so it’s a very big difference.
When it comes to thermal barrier protection for foam plastic we can talk about prescriptive thermal barriers, alternate thermal barriers, and special approvals with intumescent coatings, but it is important to understand there are differences between each of these.
This is Robert Naini, your Spray Foam Advisor, and the guy in the Hawaiian shirt, thanks for checking me out and catch me on some more videos.
