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Last Updated: , Created: Thursday, January 31st, 2002

How do you insulate an electrical mains box on a concrete wall?

Kathy writes: "My electrical box is located in the "finished" half of my basement, however it is attached to the bare cement block wall and has a particle board cupboard built over it. I am getting cold air from the wall and presumably moisture as well. How do I insulate this cupboard and since I cannot put the vapour barrier on the "winter warm" side of the box -- how do I seal it?"

Typical of older electrical installations, you can see how there is no way to get insulation behind the electrical box without major re-wiring to bring it forward. So how do you improve on this situation?

First notice that all around the edge of the door over this area, the framing stands out away from the wall, allowing all those wires to go where they must go. But that also means that moisture from the room can find its way right behind all the insulation on the wall, as well as allowing any cold air coming in from the wood/concrete joint above (probably not sealed before the wall was built) to flow down and through this door. The first thing I would do would be to use the foam in a can insulation to seal the door frame right to the wall, flowing over the wires. This will isolate the electrical box area from the rest of the wall, and the wall from this open door. Then weather-strip the thin panel door itself. You may have to add some framing to accomplish this but out the objective is to not allow any moisture from the basement to get to the cold panel, avoiding rusting of the electrical contacts. That will allow some heat from the room to go through the panel to keep the electrical box from freezing, but will stop moisture from getting back there. You will be protecting the panel from moisture and blocking cold air drafts into the room through the door.

The proper arrangement for an electrical panel is to have it installed on a plywood that has about 1-1/2 inch of foam insulation between the plywood and the concrete wall, and when the insulated wall is installed, all the wire holes into the wall and the house are sealed air tight to prevent moisture from getting behind the insulation.

Keywords: Insulation, Basement, Electrical

Article 1693