How to Insulate a Cathedral Ceiling with Batt Insulation

  • 5-10 hours
  • Intermediate
  • 100-500
What You'll Need
Batt insulation (Rolls or Pre-cut)
Protective gear
Utility knife
Measuring tape
Sheetrock screws
Power drill w/Phillips head bit
Wire Fasteners
Staple gun

Installing batt insulation onto a cathedral ceiling will prevent excessive heat loss through the ceiling of a typical wood frame house. The batt batt insulation must have the appropriate resistance or “R” value to be effective. Using the simple steps listed below as a guide, the average homeowner should be equal to the task.

Step 1 - Obtain Protective Gear and Handle with Care

When handling batt insulation, always keep your skin covered and your eyes protected with goggles. Many types of batt insulation consist of a fiberglass material. During installation, the material will scatter fine air-borne particles that can cause irritation to the eyes, throat and skin.

Step 2 - Determine the Level of Insulation Needed

A basic rule of thumb is to use R-30 or R-38 batt insulation for ceilings or attic spaces. The resisting ability of batt insulation is measured in inches of thickness and R-38 will give about the highest level of insulation. Since heat always rises, most of the heat loss is through the roof. The larger dimensions used for roof rafters (2 x 10-inch or 2 by 12-inch) will accommodate this added thickness. Batt insulation is available in widths of 12 inches, 16 inches and 24 inches, depending on the spacing between the roof rafters. Batts can be either unfaced or faced with an impervious material that acts as a vapor retarder. Faced batts are generally used for ceiling applications.

Step 3 - Prepare the Batts for Installation

Use a utility knife to open the package and allow the batts to expand, taking care not to cut into the facing or the insulation. Don’t allow the batts to get wet or become compressed; this will decrease its R-value. If the batts are purchased in rolls, use the utility knife to cut each batt to length. If possible, use a full length from the ridge of the cathedral ceiling to the wall’s top plate.

Step 4 - Install the Batts in the Cavities between Roof Rafters

Install the insulation with the faced side adjacent to the conditioned interior space. The batts are secured to the rafters by stapling through the flange of the facing material into either the edge or the face of the framing member. Wire fasteners can also be used to hold the batts in place. Do not stretch or compress the batts during installation. Each batt should fit snugly into the cavity between the roof rafters. Gravity will pull the batts down toward the ceiling—make sure that the batt is fully expanded to fill the entire depth of the cavity.

The installation is complete when there are no gaps or voids anywhere along the plane of the ceiling. Once the insulation is in place, install sheetrock in 4x8 foot sheets so that the seams fall on the bottom edge of the rafters.