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The Home Depot

How to Install Fiberglass Insulation

Pro Referral > Home Guides > Insulation > How to Install Fiberglass Insulation
How to Install Fiberglass Insulation

Insulating a home is one of the most important steps to take in maintaining the temperature of the conditioned living space. Proper insulation can improve your comfort inside and help reduce energy bills by preventing outside temperatures from affecting the indoor climate. There are several forms of home insulation available to consumers, and the simplest to install on your own are batts or rolls.

Materials Skill Level Estimated Time
• Straight Edge Beginner 3 to 8 hours
• Staple Gun
• Putty Knife
• Utility Knife
• Protective Gear

Although there are many types, fiberglass is the most common material used in batt and roll form. It is affordable and easy to install, but it can be irritating so be sure to wear gloves, long sleeves and pants, eye protection, and a dust mask or respirator when handling fiberglass insulation. For the installation you will need a utility knife, tape measure, putty knife, staple gun, and a straight edge, such as a four-foot framing or drywall square, or even a long board.


Fiberglass batts and rolls are available in standard widths designed to fit between studs and joists, and batts are cut to length for standard eight-foot wall heights. It will be necessary to do some cutting though, whether to cut rolls to length or to fit the insulation in narrow or short cavities and around electrical boxes.

Installation Process

Follow the steps below to install fiberglass insulation.

  1. 1.Cut the Insulation to Fit

    To cut the insulation, lay it on the floor with the faced side down and transfer the needed measurements to the insulation by making small cuts with your utility knife—allow an extra 1/2” to 1” for a snug fit. If you are working on a finished floor, rather than a subfloor during construction, lay down a piece of plywood to create a safe cutting surface under the insulation. Place a straight edge along your marks or cuts, press down to compress the material, and cut along the edge with the utility knife, making sure to cut completely through the facing.

  2. 2.Place the Insulation

    Fiberglass insulation can be held in place by friction, so in most cases fitting it in place snugly is adequate, but be careful not to compress it. To fill narrow cavities around doors and windows or where walls meet, use a putty knife to gently push strips of insulation in place. To secure faced fiberglass insulation, simply open the folded tabs of facing along the edges and staple them to the studs on each side.

  3. 3.Work Around Wiring and Plumbing

    It is important to properly insulate around wires and pipes to avoid leaving gaps or compressing the insulation, which can reduce its effectiveness. To install the insulation, simply divide it in half by separating the length of material. Weave the unfaced portion in place behind the pipes or wires, being careful not to compress it, and install the remaining faced portion in the cavity as normal over the pipes or wires. An alternative for working around wires is to simply slice the insulation fibers (without cutting through the facing) at the location of the wires and gently work the material into place around them, installing as normal.

  4. 4.Cut Around Electrical Boxes

    To work around electrical boxes for outlets and switches, fill in the area behind the box with expanding spray foam or a small piece of 1” foam board, measure and cut the insulation to fit around the box, and install as usual. Do not press fiberglass insulation in tightly around the box or allow any insulation inside the box.

Level of Difficulty

Installing batt or roll insulation is a home-improvement task that is suitable for homeowners of all experience levels. Fiberglass can be irritating to the skin and eyes and cause inflammation in individuals with respiratory sensitivity or asthma, so it is essential to take precautions when handling the material. The most common complaint from handling fiberglass insulation is itching of exposed skin, so covering your skin and washing up after the job is done is generally enough to prevent problems.


An alternative material that is easier to handle and is less likely to cause irritation is rigid foam insulation. Rigid foam is typically more expensive than fiberglass rolls or batts, but has a higher R-value per inch and can be installed in a very similar manner with basic skills.


If installing fiberglass insulation is something you would rather leave to a pro, you can expect an experienced contractor to get the job done quickly and neatly so you can be on your way to improved comfort and lower energy bills in no time!

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