Hello again,

I am getting ready to wire my basement, and I heard that I need to do something "special" around my electrical boxes when it comes to insulation/vapor barrier.

I really don't know how to ask, but hopefully this will be enough for someone to help?

Sorry for the lack of details, I just don't know how else to put it.

Thank you,
Nic

 

And who told you this?
Never heard of such a thing, tried asking the local building dept?

 

Maybe I am completely wrong.

Maybe it's just about putting acoustiseal around the box once the drywall is on to keep the drafts out...

 

You need to insulate behind the boxes, is that what you are asking about? Obviously, the vapor barrier, if you have one, will have to be cut to the opening of the boxes.

Never heard of it.

 

What you are probably reading is the need for an air barrier. If humid basement air is allowed to circulate up against a cold foundation it can deposit unwanted moisture. They make air sealed electrical boxes for that purpose. You also need to seal around the boxes and be sure the drywall is sealed to the framing.

As for any vapor barrier you need to verify your local code requirements. If your insulation is fiberglass up against the concrete that can be an issue as fiberglass will allow circulation within the wall. Cool air from the top of the cavity can drop forcing the warmer below up to the colder surfaces. That warmer air will have picked up moisture from the concrete and then deposit it to the colder exposed surfaces at the top. One of the recommended insulation approaches is to first apply a layer of rigid insulation over the concrete to eliminate the above issues. Then the studs and batt insulation. Using a vapor barrier runs the risk of trapping moisture between the vb and the concrete.

Bud

 

You need to wrap a peice of vapor barrier around the back of the box so you can seal it to your finished vapor barrier.

 

I think that's actually what I was looking for.

No worries about the insulation, it will all be up to code (1 inch extruded polysterene, tuck taped, framed on top of that, comfort bat, 6 mil vapor barrier). I am now done framing, and I am planning to do my electrical putting my bats and vapor barrier.

Vapor barrier around the back of the box - good call keith, thank you very much!

 

That is standard practice in my area. cut 2' squares of 6mil poly, and put it between your box and stud when you attach the box. You can get pre formed plastic vapour barrier boxes that a standard box will fit in, but they are not really worth the extra money.

Remember when you run your wires into the box, they need to go through the poly and into the box, dont run your wires behind the poly and into the box or you will end up having to cut the plastic when it comes time to seal it.

 

Good tip!
Thanks for the help Boss!

Also, when I run my wire, do I have to run them inside the studs, or is it OK to run them behind, in between the framed wall and the foam?

 

Run them through the studs. There should be no significant space between the wall studs and foam. If there is, you need to be sure to fill that space with insulation.

 

10/4 !