Working Around Obstacles
It’s tempting to just stuff insulation around any obstacles in a stud cavity. But this will compress the insulation, reducing its effectiveness, and creating weak spots where heat can travel through easily.
So you need to gingerly work the fiberglass around obstacles.
To work the insulation around cables and thin pipes inside the walls, start at the bottom or top of the batt, split the insulation into a front layer and a back layer and peel back the front layer as far as you need.
Install the back layer first, tucking it behind the pipe or cable. Then flop the front layer down in front of the pipe or cable.
To insulate around an electrical box, cleanly cut out the insulation, all the way through the batt, at the location of the box.
Take chunk of insulation you’ve just cut out, peel away about half of the thickness, and gently tuck what’s left behind the box.
Then install the rest of the batt, with the notch or hole fitting around the box.
Watch the video for demonstrations of both of these techniques.