If you are serious about insulating then you are serious about creating a good vapour barrier in the inside of the insulation. The vapour barrier is only as good as long as you minimize the number of holes through it.
All the electrical boxes represent a huge hole in the vapour barrier. It is key that vapour barrier be installed behind every electrical box. The picture illustrates what my electrician did for every electrical box he installed.
When you come to install the vapour barrier, sealing these holes is a snap. All you will have to do is cut a small slit in the vapour barrier, pull the small sheet behind the box through the hole and seal it with acoustic sealant and/or tuck tape.
Again it pays off to plan ahead! Trying to retrofit vapour barrier behind the box after it is in place is near impossible.
Coming in future posts: Vapour barriers for electrical boxes are not the only place to insert them prior to insulating. In future posts we will explore more tricks to make it go smoothly.