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.

 

[zzvyb6]

If thats a full basement or a crawl space, go look there to see if air is coming in (or going out) via the foundation plate. Since you say frost forms on the wallplate cover, I'd presume that humid interior air is leaving at that point. Many times, insulation is poorly installed there. And, air is probably following the wiring through the studs. Also check the attic. Air under pressure can find its way quite a distance. I'd send a can of foam along the outside of the electrical box (from the inside wall) on all sides. You can find extra-wide cover plates if you have to knock out a little drywall to get the job done. Also check the bottom of the siding on the outside where it meets the cement block. This is a notorious place for winf to enter. I have no problem with stuffing the box with glass insulation.

Check with your local fire department. They may have a F.L.I.R. gun or camera which can be used to locate the cold air chute. Forward Looking Infra-Red cameras are used to find fire in walls and bodies in burning homes. Some Utility companies will bring one when they come out to sell you inulation packages. The heat patterns may be able to tell you where the problem actually is.

 

[JDgreen227]

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

I


I like that idea...little mess and no damage and the wall is 2X4...another post asked about possible air infiltration from above or below, very good point. The interior wall area above the switch box is reasonably warm while the wall area below the switch box feels about 10 degrees colder than the upper area. The construction was a do-it-yourself project as was the insulation and I could have sworn we insulated fully inclusive of tucking a strip of fiberglass behind the boxes. I did all the caulking on the sills of the entire basement but because the basement walls and ceilings are studded, insulated, and drywalled it would a huge PIB trying to find a source of infiltration from underneath. Thanks to all, you have given me a lot of advice !!!

 

[Dutch445]

when you describe the location of the switchbox, is it on the same wall as that window? if so, could it be directly above that
black wire looking thing coming out of the siding near the bottom of the siding?
i would almost think that for now, get the foam insulator for under the cover,
and in summer start taking things apart, if you have that much air blowing thru,
then i doubt it has to do with the insulation around the box, but that
entire bay may have been missed, and/or there were some other areas that
weren't sealed well, maybe around the window. air could follow behind the
siding to a sheathing seam etc. but it sounds like a pretty substantial leak
on that side of the house.
the good thing, it's fairly easy to remove siding, and between the corner and window
is a piece of cake, you could do that this summer and see how everything is taped up
and how the housewrap looks

 

[JDgreen227]

when you describe the location of the switchbox, is it on the same wall as that window? if so, could it be directly above that
black wire looking thing coming out of the siding near the bottom of the siding?
i would almost think that for now, get the foam insulator for under the cover,
and in summer start taking things apart, if you have that much air blowing thru,
then i doubt it has to do with the insulation around the box, but that
entire bay may have been missed, and/or there were some other areas that
weren't sealed well, maybe around the window. air could follow behind the
siding to a sheathing seam etc. but it sounds like a pretty substantial leak
on that side of the house.
the good thing, it's fairly easy to remove siding, and between the corner and window
is a piece of cake, you could do that this summer and see how everything is taped up
and how the housewrap looks

Good point, and the switch box is located on same wall as the window and basically behind the inside corner trim of the siding. The black wire is a 10 year old cable that was run in from a dish at one time and has been heavily caulked. Although the sill of the concrete block wall has also been caulked and it has been fully insulated both in basement as well as above ground, the block foundation on the window side of the picture dates from 1951 (!!!!) and there may be cracks I am unaware of.

 

[Gunny]

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

Yessir, make sure you use the minimal expansion foam, I've saw one home where they had this same problem and used the regular foam, really blew it in there and popped the drywall away from the nails!

 

[JimRB]

If you do not have house wrap on the outside one might argue the house is not properly insulated. One problem with fiberglass insulation is air infiltration. Second is some installers just wad the stuff up behind electrical romex, water pipes or other obstacles instead of making slits to encapsulate the obstacles. But you still have air infiltration issues. That is why some folks do the hybrid spray foam first to stop air infiltration and then fiberglass. My house has blown in cellulose that is not supposed to have air infiltration problems like fiberglass but I suspect the cellulose insulation has sagged in some area that I cannot see. I did not know about the house wrap and failed to do it. It will be done if/when my siding needs to be replaced. We did caulk all bottom and top plate penetrations but lots more air sneaks in behind/around the outside plywood and foam board.

By the way I would have made a few 1/4" holes around the electrical box, inserted the low expanding foam straw and squirted foam around the box. The little holes would get sealed back up by the foam. I would also have done a squirt around where the Romex comes into the box and any other holes in the box. Same as what others have suggested. The bigger issue is if you see that much of a breeze via the electrical box you may very well have an insulation system that is not working well at all.

I keep saying I want to get an infrared thermometer to measure the house either in the dead of winter or just after sunset on a 100 degree day to see where the house is leaking heat or cool. The fancy infrared cameras would be a neat gadget but they are expensive.

 

[JDgreen227]

Original house was 2X4 construction with ZERO wall insulation and about 6" of rock wool in the attic. Back about 1993 I removed the weathered cedar siding and then the sheathing on the walls, rewired the entire house, added wall insulation then used 3/4" plywood sheathing to replace the original 1X6 boards. In the attic I spent a lot of time removing and disposing of the rock wool as there was no vapor barrier, then I added first R-23 fiberglass with a vapor barrier and covered that with R-16 unfaced batts. Made a HUGE difference in the heating bills. When I added on back in 2002 I wanted to use 2X6 studs but my ex-wife's brother said it would take a long time to get back the added cost of the thicker studs and insulation and interior window trim...and my ex sided with him. No, we did not use housewrap either. DARN.