Can I spray-foam behind a sub panel?

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  #1  
Old 11-13-13, 08:15 AM
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Can I spray-foam behind a sub panel?

I have about 1/2" gap between the sub panel (between the studs) and the sheathing behind it and I would like to use a low expansion foam (for windows/doors). Of course I will seal the screw holes on the back with painter's tape before that, but other than that is that OK to do? Unfortunately I did not remember to look behind before installing it and not sure if there are other holes hidden behind the black plastic base where the breakers are.
Note - I am talking about behind the panel, not above it, where there will be another piece of Roxul.

Thanks!
 
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Old 11-13-13, 09:05 AM
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Can you slide a piece of rigid foam in instead, or just take the subpanel loose long enough to do that? It's doubtful that pieces of masking tape on the inside will block the foam effectively, there are probably some hidden holes - as you suspect - and it's also unlikely that you can get full fill if you do it with the subpanel in place. But in general, yes. Electrical panels have been surrounded by sprayed-in foam insulation.
 
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Old 11-13-13, 09:25 AM
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Unfortunately I can't do either of the other options. Not enough space (and couldn't find 1/2" rigid foam) and even if I did have that, it would probably get ripped while sliding it. And I am not taking the panel off, too much work
I'll try to look at a similar panel in HD later to see if there are any holes that I can't see from the front.
As for painter's tape - it definitely blocks the foam, I used it in larger gaps with the expansion foam and it blocked it completely.
 
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Old 11-13-13, 09:40 AM
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Then stuff fiberglass insulation behind it.
 
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Old 11-13-13, 09:53 AM
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I am not taking the panel off, too much work
Really? Looks like four screws and it's loose enough to work behind.

couldn't find 1/2" rigid foam
Did you look at Home Depot? Super TUFF-R R-3.3 1/2 in. x 4 ft. x 8 ft. Foam Insulation.

The problem with stuffing fiberglass insulation into any space is that when it's compressed - and it will be here - it loses its insulating value. It's the trapped air in the fiberglass that slows the heat transfer down.
 
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Old 11-13-13, 10:21 AM
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Really? Looks like four screws and it's loose enough to work behind.
Right, but it was (and will be again with all the wires) a big PITA to put in and align for the 1/2" blue board with my old and uneven stud work.

Are the only issue that you guys having is the hidden holes (if any)? If there aren't any hidden holes (which I will verify by checking a similar panel at the store) and the all visible holes are blocked, is there any issue with spray foaming behind it?
 
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Old 11-13-13, 11:46 AM
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If there aren't any hidden holes (which I will verify by checking a similar panel at the store) and the all visible holes are blocked, is there any issue with spray foaming behind it?
Other than getting the space filled? No.
 
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Old 11-13-13, 03:44 PM
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I've seen it done at work plenty of times when our panels were mounted in steel stud.
A guy would go around and slap that goop tinbashers use to seal their duct (do not know the official name) on the back of our tubs to cover any small holes and any EMT connectors, then once a layer of board went up they would sprayfoam behind it.
 
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Old 11-13-13, 04:01 PM
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Try some Vermiculite. It should just pour into the space. The bottom edge would need to be sealed.
 
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Old 11-13-13, 05:06 PM
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I can picture Vermiculite trickling into the panel for years to come.
 
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Old 11-13-13, 06:36 PM
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Done and came out perfect!

Turns out there were 4 invisible holes behind the plastic breaker assembly: 2 are used by the screws that hold the assembly. Another 2 are above it, probably for a different type of breaker part.
I took the two screws out, pulled the plastic and covered all holes with painter's tape and sprayed behind the sub and on the sides. Three hours later I removed the tape and put everything back. Based on the 'view' through the exposed holes, the entire back of the sub is covered. Should be a nice seal.

Thanks again.
 
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Old 11-13-13, 06:37 PM
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Having tried spray foam using an extension nozzle I would doubt that you would get good coverage with the panel in place. I would pull the panel out and slide the foam behind it and just seal the uneven spots with the spray foam.
 
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Old 11-13-13, 06:42 PM
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I think I'd rather see the foam used as vermiculite which is associated with asbestos in 70% of the vermiculite used up through 1990 in this country.
 
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Old 11-13-13, 07:06 PM
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I had the same thought CJ. I remember playing in that stuff as a kid.
 
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Old 11-14-13, 04:40 AM
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Having tried spray foam using an extension nozzle I would doubt that you would get good coverage with the panel in place.
I sprayed from the top and bottom and based on what I see, and the expansion, it is covered pretty good. Not trying to get a high R value, just prevent draft and a pocket of freezing air behind the metal box.
 
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