Romex going thru closed cell foam


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Old 07-18-23, 10:45 PM
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Romex going thru closed cell foam

This is hard to explain, so bear with me...

This is a new home under construction. Electrical rough-in currently in progress. The load center is in my attached garage. It is recessed into the wall between the garage and the house (living area). The wall itself is actually two 2x4 walls (side by side) with 1/4" Thermo Ply between them. The wall will be insulated with 3" thick closed cell spray foam on the living area side of the double wall. The Thermo Ply sheathing is there to give the insulator a surface to spray against and to keep the insulation out of the garage side wall. Hope that part makes sense.

The Romex cables coming out of the load center for the house circuits will have to penetrate the closed cell foam to get from the load center to inside the house. I'm trying to figure out the best way to do these penetrations such that it makes it easier for the insulator to do a good job of sealing the penetrations, and it allows for future wires to be pulled through the closed cell foam. Note that this is about running the cables through the foam, i.e., from one side of the foam to the other side.

The only idea I came up with is to run the cables through short (12") pieces of PVC conduit to get from one side to the other. I might have a shortfall of knockouts in the load center for that.

Any other best practices/ideas on how to do this?

Thanks,
ibroussard
 
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Old 07-19-23, 01:41 AM
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The cables are normally run first and the insulation sprayed afterward.
 
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Old 07-19-23, 05:24 AM
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Before insulating make sure there are outlets and switches wherever you think you might want them. In a fiberglass or cellulose insulated home it's relatively doable to pull wires through the walls to add something. Spray foam insulation makes it extremely difficult to make changes in the future.
 
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Old 07-19-23, 08:36 AM
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I pretty much understand all of that. I'm specifically looking for ideas on how to insulate around the 30+ Romex cables coming out of the load center that need to penetrate the closed cell foam insulation in the wall behind the load center. Is running the Romex through many short runs of PVC conduit the best (or only) solution?
 
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Old 07-19-23, 09:07 AM
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No, it's best for the foam to expand and seal around the cables. It's really no different than all the wiring in the walls. If you run them through a conduit there is an air space between the cable and conduit that is not sealed.
 
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Old 07-19-23, 09:57 AM
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Agreed, I wouldn't sleeve the cables just to get through the foam. I'd run the cables through the plywood wall, then use firestop caulk to seal the holes before the spray foam comes in.

I'd also consider running 1 or 2 extra runs of empty 3/4" conduit from the panel to the attic or closet or somewhere reasonably accessible to allow pulling wires in the future. For a circuit for charging the robot butler or whatever newfangled thing comes in the future. BUT I wouldn't go overboard future-proofing.
 
 

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