Is spray foam safe around electrical wiring?

[Dave Kowalski]

About to do my attic with DIY open cell. There is existing Romex wiring stapled to the rafters. Is it safe to spray foam over or around the wiring? Any concerns?

[Rex Harrington]

General rule: you should not embed wiring inside spray foam unless the wire is properly derated for reduced heat dissipation. The NEC has specific rules under Article 310. Encasing Romex in foam reduces its ability to shed heat.

[Nick Patel]

This is a real code issue. If you spray over Romex in an attic it may need to be re-rated. Most AHJs want wiring in conduit if it is going to be embedded in foam.

[Amy Chambers]

In practice a lot of attics have foam sprayed around existing wiring and nothing bad happens. But from a code standpoint foamologist_rex is right. Check with your inspector first if permits are involved.

[Dave Kowalski]

Good to know – I will spray around but not over the wiring where possible. Thanks for the heads up.

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