According to the January 2016 edition of Electrical Currents, a newsletter from Stephen Thornton, the chief electrical inspector for the Washington State Department of Labor & Industries, many questions arise among electrical installers when it comes to the use of polyurethane spray foam insulation in residential construction. Specifically, many are unsure whether nonmetallic-sheathed cable is allowed to be in contact with, or encased in, spray-foam insulation.
The first issue is one of access to the cables to perform a visual inspection. WAC 296-46B-010(4) states “Electrical wiring or equipment subject to this chapter must be sufficiently accessible, at the time of inspection, to allow the inspector to visually inspect the installation to verify conformance with the NEC and any other electrical requirements of this chapter...” According to the report, “until all of the wiring in the areas that will be covered with spray-foam insulation has been inspected and approved for cover by the electrical inspector, the wiring must not be covered with spray-foam insulation or anything else that would conceal the conductors.”
Read the full article (on the second page of the newsletter) to learn what other two key concerns come up with installers when encasing nonmetallic sheathed cables in spray-foam installation, as well as the department's ruling on why — and under what circumstances — it will not prohibit this practice.
