When building a home, everything needs to be done in the correct order. For instance, after the framing is complete and the exterior walls have been put up, you need to consider the inside of the wall cavities before you drywall the interior. Electrical systems and insulation both need to be installed inside the wall cavities of your home, and it is important that they go in in the correct order.
It is important that wiring is done before insulation is put into place in new construction. Holes need to be drilled into the frame and wires run throughout the walls. Trying to do this kind of work around insulation would provide needless obstacles for the electricians to work around. In most cases, wiring is not a job you can take on yourself. Local code requirements typically insist that an electrician complete the job so that all safety requirements are observed.
After the wiring is in place, the insulation can be laid in. Most homes are insulated using batt or roll insulation. Other options, such as spray foam or loose insulation, are also a possibility, but in all cases the insulation needs to be installed after the wiring is done.
When you insulate around wiring, it is important that you fill as much space as possible with insulation. There are two ways to insulate around wires. First, you can tear or cut the insulation sheets in half and lay half behind the wire and half in front. If the wire is too tight to the wall to make that easy, you have a second option. Tear the sheet across the width instead of tearing it lengthwise. Then, you put the wire between the top edge of the bottom half of the sheet and the bottom edge of the top half.
Insulating Old Construction
If you are adding insulation to an older building that wasn't insulated properly or replacing insulation that is not up to modern standards, then you have the decision made for you, because the wiring is already in place. Sometimes, when the walls are already all in place it is better to use alternate methods of insulation, such as blown-in insulation. This is particularly useful when you need to fill insulation in around older existing wire systems; even if you don't know exactly where the wires run, the blown-in insulation will simply fill in the gaps.