wiring a house that is scheduled to get foam insulation

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difowler1

Senior Member
Are there any special reqirements when wiring a house that will be foamed as opposed to regular insulation? The customer says that additional vents are necessary by code in the bathrooms due to increased chance of black mold. The walls and ceiling will be foamed according to the customer.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You can use NM cable, just keep in mind the limitations of 334.80 regarding spacing and penetrating sealed holes in wood.
 

TobyD

Senior Member
Keep in mind that as the foam expands it will move the cables. Secure them well or you may have them pushed to the front of studs.

There is No moving of boxes or cable after. Make sure everything is where you want it.

Good advice.The homes we do that are foam insulated are subject to damage to the Romex brand wire.The installer actually uses a power roller or a sharp blade to shave off excess foam that expands beyond the wall stud space.By using a few extra staples may save you a lot of trouble.
 
Problem is how do you know where that something down the line will need to be located? And if you do know then why not run either pipe or cable to the location now?

Yeah, with any kind of pipe, you'll probably still need to add some raceway, and that often requires patching drywall. I do think it gets you a lot closer to your final destination before you have to fish or add on.
 

kwired

Electron manager
Location
NE Nebraska
Most spray on foam insulation I have run into is just a flash coating on the exterior walls that is not really that thick, maybe up to an inch thick, with occasional places that were hit more and are thicker. The idea is to seal everything with this relatively thin coat - but it has essentially no holes or gaps so it seals well. This is the vapor barrier and they don't put the traditional plastic vapor barrier up that used to go right under the drywall if it was flash foamed. They then fill the rest of the stud cavity with other traditional types of loose fill insulation which I'm assuming costs less or they probably would foam the whole wall. Often it is same company foaming as well as installing the loose fill, maybe not the same crew for each part but same company.


If you have a good crew they tape over your wall boxes so they don't get foam in them, though if they do get foam in them it usually is not intentional and is not all that much.
 

jnaas2

Member
Location
Evansville, In
Just fixed a house that was foamed, Wire was stapled every 3 feet and it pushed one out past the studs and had to rip the foam out and rewire it. It was very obvious since the machine tore it to shreds, Check after there done and make sure no wire was close to surface and was damaged
 
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