Replies

1. Expert Member
   MALCOLM TAYLOR | Aug 19, 2022 06:25pm | #1

   Alan,

   I don't mean to trivialize your question, but I'm reading it as "Can a new bathroom fan be installed in a bathroom?" Could you expand on what your concerns are? Is there something about where it's going that you think might pose a problem?

2. 
   alan_from_dc | Aug 22, 2022 01:53am | #2

   Thanks, Malcolm. To expand: I am replacing two upstairs bathrooms' 30-year-old exhaust fans. Will probably install Panasonic fan/light units. Will be peeling back the membrane roof, sistering the joists, and spraying in foam. And installing new roof. There is virtually no insulation up there now. ... We live in Alexandria VA.

   It these fan units used just the old incandescent spots, I would have to separate them from insulation, right? Lots of heat. These days, my guess is that the lights will be LEDs. So not much heat. But fan motors make some heat.

   So, do modern building codes, and good sense, require separation? There are, of course, "cans" you can buy to separate lighting from insulation. I am not sure whether to demand similar separation for my soon to be uber-insulationed fan units.

   And, as I am sure you and most readers know, at least in the days of cellulose and incandescents, fire was a non-trivial concern for bathroom lighting.

   Thanks for your quick response - alan

1. Expert Member
   MALCOLM TAYLOR | Aug 22, 2022 11:02am | #3

   Alan,

   The problem was mine - your question was perfectly clear once I realized what you were asking.

   Yes you can insulate the fan housing on all Panasonic bathroom fans with lights.
   https://na.panasonic.com/us/support/ventilation-faqs

3. Expert Member
   Akos | Aug 22, 2022 02:07pm | #4

   "replace the 40-yr old exhaust fan"

   By the same token, eventually even these units will need to be replaced so I would do the future a solid and not encapsulate them in SPF. Build a small cubby out of plywood or rigid insulation around the fan and spray foam over the cubby.

   Also for your roof, spray foam against the ceiling is not the same as spray foam under the roof deck. The spray foam will do a good job of sealing up your ceiling but there will be a gap between the srapy foam and the roof deck. This gap needs to be vented. Assuming the assembly bellow is air tight, it doesn't need a lot of venting but aiming for at least code min doesn't hurt.

   The one benefit of venting is that you can also use open cell SPF which has much lower environmental impact and significantly cheaper. The center of cavity R value will be lower with open cell SPF but because of the thermal bridging of the rafters, the assembly R value will be pretty close to the closed cell option.

   SPF guys love to quote the super high center of cavity R values but when it comes to energy loss (thus your heating costs) only the overall assembly R value matters.

4. 
   bennyfr | Oct 18, 2024 05:12am | #5

   Instead of an IC rating, you’ll want to ensure the exhaust fan is rated for installation in insulated areas and is approved for use in bathrooms where moisture levels are high.