Insulating drafty electrical switch box

[JDgreen227]

There is a ten year old switch box in my dining room that is in the northwest corner of my house, at the junction of an "L" and because the wind usually comes from the east, I get a draft through the box that is strong enough to blow out a match if the cover plate is off. For some reason whoever did the fiberglass insulation didn't do a good job of sealing. The metal cover plate (on a plastic box) sweats badly during cold weather. I can either pull the siding and sheathing and redo the insulation properly, or I can cut unfaced fiberglass insulation and add it to the box interior to stop the draft. Seems to me to be perfectly safe as the wiring is 12 gage and the only thing on the circuit in that room is a switched ceiling light that draws 2 amps at most, if I do plug in a vacuum cleaner to the outlet 6 feet away that will only draw 10-12 amps for a few minutes, not enough to heat up the wiring to any degree (pun intended) and the switch box is located as the last connection in the circuit.

Yet all the sources of information I read online say NOT to insulate the interior of the box...I can understand not using spray foam, but what is the danger of using fiberglass? BTW, the drywall is new, 2 layers of 1/2" and the box is an extra deep one. Any comments? Thanks.

 

[unbidden]

Are you not able to spray foam on the outside of the box using the straw applicator?

 

[JDgreen227]

Are you not able to spray foam on the outside of the box using the straw applicator?

Well, that would require removing the siding, drilling holes in the sheathing, and hoping the spray went in the proper place and I would have no idea if it did or not unless I removed the sheathing. Your idea would work well IF I had some way of knowing the spray went to the right area without uncovering it all. Thanks much for the suggestion. Let me assure you I do NOT want to pull the siding, sheathing, etc in the corner shown unless absolutely required...the switch box is about a foot higher than the exterior window frame and located behind the inside corner.

 

[grsthegreat]

you can also simply insert the spray foam nozzle between the drywall and the electrical box and spray away. fill the entire gap in the wall.

They also make insulation foam pieces that can be installed in the box before the coverplate. these really do cut down on drafts.
Electrical Outlet Insulation Foam Gasket AM55011

these do work..ive used them before. Electrical supply houses generally sell them. not sure about home depot or lowes.

 

[Coyote machine]

I'd see if it is possible to disconnect power to the outlet and then remove it and it's box and then use spray foam to seal the area behind the box where the wires run to the outlet's removed box. Then install a new retrofit box made for existing work use, and then reinstall the outlet, and an insulated outlet foam template and cover and done!

 

[JDgreen227]

Coyote machine, disconnecting power to the switch is no problem BUT it is very securely screwed to studs on BOTH sides and the drywall surrounding it is such a snug fit to the box there is no gap around it. I would not want to demolish the box and go thru the headache of replacing it and repairing the drywall. The idea of spraying foam around it may be practical but I don't want to create gaps around the box unless required.

 

[aczlan]

Coyote machine, disconnecting power to the switch is no problem BUT it is very securely screwed to studs on BOTH sides and the drywall surrounding it is such a snug fit to the box there is no gap around it. I would not want to demolish the box and go thru the headache of replacing it and repairing the drywall. The idea of spraying foam around it may be practical but I don't want to create gaps around the box unless required.

Cut power and drill a 1/4" hole in the back of the box to stick the straw through. Might also need a hole in the top/bottom depending on how the cavity is laid out.

Aaron Z

 

[jjlite]

Just wondering if you have 2x4 studs or 2x6 ? if you have 2x4 and a deep box there might not be enough room behind the box and the outide wall for insulation you may be best off to cutpower and insall a shallower box. Being the end of the end off the line you sould be able use a shallow box with ease To get the old box out use a hack saw blade on each of the scews.Just my two cents 1hr job compared to who knows on the siding.

 

[GBOUTDOORS]

It sounds like you do not want to touch the box at all so aczlan has the right fix for you just kill the power drill three holes, top, mid.,bottom of box and use Low expansion foam made for around windows. DO NOT use the regular high expansion as this could make a bigger problem then what you have now I have had guys blow the sheet rock off the wall by using the wrong foam. This is and should be a very easy fix.

Ps as an after thought if you are worried about the foam you can also get the red fire retardant foam in low expansion.

 

[murphy1244]

Be carefull with that spray foam, I blew out a door jamb first time I used it.