Correct Method Photo Source: Summerhill

Incorrect Method Photo Source: Summerhill

Using batts in a wall cavity with wires:

Batts should be cut horizontally on the opposite side, from that which will be placed into the wall. This will allow you to see the cut and insulate around wires without compressing the batts. It is important to cut the batt BEFORE placing it in the wall as cutting it after installation may lead to cutting of the electrical wires creating a hazardous situation. Alternately, you can split the batt so that one half is installed behind the wires while the other half is installed in front of the wires. Never try and fit the insulation behind or in front of a wire. Placing the insulation behind or in front of a wire will cause compression, and create a large air space behind the insulation.