We recently installed new electrical boxes and hung fans from them. We caulked around the boxes to seal off airflow into the attic. There are several small holes (and one has a medium sized hole) on the boxes. What's the proper way to seal this off to prevent the blown-in insulation from falling through the hole into the box (a fire hazard I presume)? Is caulking them appropriate or just putting a piece of electrical tape over the holes?


Using foam in a can, like Great Stuff http://www.homedepot.com/p/GREAT-STUFF-Big-Gap-Filler-Insulating-Foam-Sealant-16-oz-248314/100029171 can be used to fill in gaps to help prevent air leaks.

  • The page you linked to says it's for "gaps larger than 1 inch". That's a pretty big hole for an electrical box. – Niall C. Jul 7 '14 at 14:07
  • There are multiple varieties of spray foam (including from this one company) for various applications. Read the labels, pick the one that suits. Though I'd note that any other form of caulking would also work Just Fine... and that blown-in insulation is supposed to be fire retardant. – keshlam Jul 7 '14 at 14:17

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