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Insulation Termination


Bronze Member
Dec 8, 2009
How are designers, plan reviewers and contractors handling the termination of slab edge rigid foam insulation on the interior of the building?

2015 ICC codes. 2015 IECC, Section R402.2.10, Slab-on-grade floors, permits residential insulation to be cut at a 45-degree angle to allow the floor slab to extend to the exterior wall.

Section 402.2.5 for commercial compliance does not permit this.
Looks like nobody bit on this but it is a good question. I typically don't get too worked up over it where the insulation is terminated below the top of the slab at the occasional door or storefront, but I have a building that is at least 50% storefront. They take credit for the slab insulation for the entire perimeter in the COMcheck, but terminate it below the interior or exterior slab at the other 50%. Easy enough to protect it on walls, but where the storefront track sits on the turn-downed slab it is uglier. Chamfering at the 45° angle like in the residential code might work but is destined to crack and be really ugly.

The easy solution would be to take credit for the percentage of perimeter insulation that is compliant and take 0' for the non-compliant, but they are at 1% better as is so they would need to find other areas to off-set the loss. I have never liked this particular requirement because of the practical difficulties with the installation of it in situations like this, although I understand and don't disagree with the reasoning.

I don't see a change in the '21. I can't find a code change proposal for the 24 IECC, but all those documents have become pretty jumbled to the point I'm not even sure where to look anymore.