Cutting Batt Insulation

man installing batt insulation
  • 1 hours
  • Beginner
  • 30
What You'll Need
Batt insulation
Carpenter's square
Utility knife
Measuring tape.
What You'll Need
Batt insulation
Carpenter's square
Utility knife
Measuring tape.

Batt insulation, sometimes referred to as roll or blanket insulation, is pre-sized insulation used in home construction. It is most commonly used in attic, wall, and floor installation due to its available sizes. Batt insulation can be made of various materials such as plastic, wool, cotton, and mineral fibers, but the fiberglass type is the most often used in home improvement and new construction projects.

Batt insulation is measured by its thermal resistance or R-Value. A higher R-Value means a higher thermal performance level as well as a higher cost.


Batt insulation can be purchased from most home improvement stores, lumber yards, and contractor supply sites. Before purchasing and installing check the manufacturer’s instructions to ensure that you are using a batt with the proper R-Value based on your needs. Batt insulation can be purchased with or without vapor barrier facings or linings.

The facing provides a vapor and air barriers to help increase the effectiveness of the insulation. Most commonly, facing or linings are made of kraft paper, foil paper, or vinyl. In some cases, the facing also serves as a fastener to make installation easier. Flame retardant facing is also available if batt insulation is being used on an unfinished interior wall.


safety gear

Working with batt insulation can be dangerous due to the risk of skin irritation from the fiberglass as well as possible injury while trying to cut this dense material. Please use caution while working with this material. Please consult a local contractor if you have any questions, and always check building and fire codes before installation of this product.

Here are a few helpful tips and guidelines to use while working with this type of insulation


Use a measuring tape to measure the width and the length of the joist or space where the batt insulation will be installed. Make a note of the measurements to ensure the proper size before you begin cutting.


Insulation and tools

Before beginning this project, put on protective clothing, gloves, goggles, and mask to protect yourself from irritation and inhalation of harmful fibers.

Layout the insulation paper-side up on a hard and level surface. If working on a finished surface use a piece of plywood underneath to protect it from getting nicks and cuts.

Use your knee or a heavy object to secure the insulation before you begin cutting.

Once the proper measurements are marked on the batt insulation, use a knife such as the popular Olfa knife, with a fresh sharp, and long blade, long enough to make a clean cut through the thickness of the insulation.

Cut the insulation using short steady strokes utilizing a metal ruler or carpenter’s square as a guide as you cut along the length.

Apply pressure to the ruler or carpenter’s square as you cut to condense the insulation for easier cutting.

Give a few inches of allowance on either side of the batt insulation to ensure proper fit and allow for any discrepancies in measurements. Any excess insulation can be easily tucked in to fit, preventing gaps between the studs and the insulation.