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Thursday, January 11, 2024
Question:
Good morning, I read your forum every morning and look forward to it. We had some questions come up during a recent energy conservation meeting. We are running into a high use of spray foam insulation due to the new energy codes. Is it addressed in the
NEC® as to encapsulating any wiring of any type due to the possibility of overheating. Thanks in advance, Richard P.
A
Answer:
Hello Richard, glad to hear you are enjoying the CQD. In general, the
NEC® does not prohibit the installation of NM Cable incapsulated in spray foam. There are rules pertaining to ampacity adjustment when cables are bundled in Section 310.15(C)(1). This becomes a manufacturer and product listing issue and the manufacturers of Type NM Cable do permit the cable to be encased in spray foam. This is a topic of concern that dates back to 1985, when testing was conducted by the University of Toronto on the potential overheating effects of Type NM-B Cable encased in spray foam. The findings were favorable showing maximum temperatures far below the 90º C rating of NM Cable insulation. This information can be reviewed in the
NEMA Bulletin on the Thermal Effects of Residential-Installed Type NM-B Cable Encased in Spray Foam Insulation.