Question
Has UL investigated the effects of spray-on foam insulation on Type NM cable jackets or individual conductor insulation?
Answer
UL has not specifically investigated the effects of spray-on foam building insulation on the jacket or insulation materials of NM cable. UL Lists NM cable under the product category Nonmetallic Sheathed Cable (PWVX), located on page 293 in the 2011 UL White Book and online at www.ul.com/database and enter PWVX at the category code search field. Type NM cable is evaluated for compliance with theStandard for Safety for Nonmetallic-Sheathed CableANSI/UL 719 for installation in accordance with Article 334 in theNEC. UL 719 does not address testing Type NM cable for spray foam building insulation compatibility.
UL is not aware of evidence that would suggest chemical corrosion. Once cured, these spray-on foam materials are inert solids and are not expected to effect the PVC insulation or jacket. While the curing process varies with the type of spray-on foam, the curing process usually begins immediately after application, with the foam being fully cured in 1 to 12 hours. Since the majority of these products do not contain volatile organic compounds (VOCs) or formaldehyde, these foams, in the non-cured state, are currently considered compatible with the cable insulation and jacket.
There have been noted cases of conductor insulation/jacket damage in installations where spray-on foam was applied in direct contact with insulated cables. It is possible that the damage noted is from incorrect application of the spray-on foam insulation, applying more spray-on foam in a single pass than recommended. Not following the manufacturer’s recommendations by applying the spray-on insulation in too thick of a layer could result in higher curing temperatures that may damage building materials, including electrical cables. Damage that is a result of thermal heating due to the curing process is consistent with the type of damage reported.
