Working with fiberglass is easy. Professional installers use a regular knife to cut the batt material. The knife has a six inch long blade that is fairly sharp, but not as sharp as a new razor knife would be. It readily cuts the material. Using a razor knife to cut thick batts can often require two or three passes.
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If you install batts in your attic rather than blown-in insulation, you need to take your time. A tight fit around any object that sticks through the insulation is essential. I suggest you do this type of work in cool weather when your patience will not be affected by your comfort!
You should also consider just how you are going to get the material into your attic. Many attic access holes will not provide enough room to fit a rolled up batt! Be sure to check this out or otherwise you will be tracking unrolled material through the house. Fiberglass fibers will be everywhere!
Fans and Recessed Lights
Insulation traps heat. This is good for your house but can cause fires if you cover fans and recessed lights that contain older wires. The heat from fan motors and light bulbs can easily create temperatures that will melt insulation and cause fires! If you are in doubt about what to do, ALWAYS check with a code official or build a sturdy plywood box over the fixture. Provide at least 12 inches of space between the box and any fixture part. You can then insulate over the top and sides of this box. The air space will help dissipate the heat.