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I'm installing low-profile (slim) recessed LED IC-rated lights in my living room that has a drop ceiling. Above the area that one of the lights will go is a plastic sheet seemingly filled with old lathe and plaster (no idea why). I can't tell how much garbage is actually up there so would rather just leave the plastic alone.

Is there any problem with pushing the recessed lights into the hole right up against the plastic sheet? I know IC-rated means that it can come in contact with insulation - what I'm not sure about is how IC-rated fixtures differ across other materials.

  • It's hard to answer without knowing what kind of plastic it is... are we talking about 6mil vapor barrier, or something more substantial? – User95050 Oct 13 '18 at 17:37
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Go ahead, although I'd stick a thermocouple up there and double check the temperature to be sure

NEC 410.116(A)(2) permits IC-rated recessed fixtures to be in contact with combustible materials in the manner you describe:

(2) Type IC. A recessed luminaire that is identified for contact with insulation, Type IC, shall be permitted to be in contact with combustible materials at recessed parts, points of support, and portions passing through or finishing off the opening in the building structure

As a precaution, though, I would use a cheap type-K thermocouple probe and meter to measure the temperature at the light-to-plastic interface after the light's been left on for a few hours -- anything under 90°C should be fine, as per NEC 410.115(A):

410.115 Temperature.

(A) Combustible Material. Luminaires shall be installed so that adjacent combustible material will not be subjected to temperatures in excess of 90°C (194°F).

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Looks like it is specified in code. This should not be done according to the following. Looks like 1/2" is minimum with anything combustible other than insulation.

NEC 410-66 - Recessed lighting fixtures installed in insulated ceilings or installed within one half inch of combustible material shall be labeled as Type IC (insulation contact). In addition, your state Energy Code requires recessed lighting fixtures in insulated ceilings to be sealed to prevent leakage of airborne moisture.

  • Your NEC quote is obsolete (the relevant section is 410.116 -- there is no 410.66 any longer), and I believe you're misinterpreting it as well... – ThreePhaseEel Oct 13 '18 at 18:26

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