How to Install Insulation in Open Walls

Installing Batt Insulation in Walls

Don Nichols/Getty Images

Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 1 - 2 hrs
  • Skill Level: Beginner
  • Estimated Cost: $.30-1.50 per square foot

Insulation is the home improvement that keeps on giving. It keeps you comfortable, saves you a fortune in heating and cooling costs, and even buffers noise within your home.

Insulation is very easy to work with. It doesn't require strength or tremendous skill. The rolls or batts should fit snugly between the studs, and the only trimming you'll have to do is around windows, door frames, electrical outlets, and plumbing. It cuts easily with a utility knife and is extremely lightweight.

Insulation R-Value

Before shopping for insulation, it is important to understand its R-value or its resistance to heat flow. The higher the R-value, the greater the resistance to heat loss. The Federal Trade Commission mandates that each package of insulation carry a label that includes its specific R-value as well as health and safety precautions.

Which R-value is right for you? That depends on several things, including where you live and what type of heating system you have, as well as whether you're insulating for energy efficiency (a wall along the exterior of your home) or noise reduction (interior walls).

The US Department of Energy has created a zone map on its website with corresponding R-values to help homeowners determine minimum insulation values.

Kinds of Insulation

Loose-Fill and Blown Insulation

Because it is forced through a tube and blown into space, loose fill is best suited for unfinished attics and hard-to-reach areas. Loose-fill insulation cannot be used with open walls, as the insulation needs to be confined for it to stay in place.

Fiberglass Rolls and Batts

Blanket-type insulation comes in two forms: rolls and batts, either of which is a good choice for insulating interior open-stud walls. Both rolls and batts—a rectangle of insulation, sold flat in packages—typically come in 8-foot lengths, a standard ceiling height. Insulation is sized to fit between studs, usually spaced 16 or 24 inches apart; be sure to measure the space between the studs before buying.

Insulation Facing and Vapor Barriers

Insulation batts and rolls are available either with face coverings or without. Brown Kraft paper is a common facing. Fire-retardant foil sometimes is used to cover batts that will be left exposed in unfinished spaces, such as a garage or basement. Insulation also comes wrapped in plastic to protect you from the itchy fibers, which is a good choice for first-timers.

Insulation facing is intended to serve as a vapor barrier that helps to keep interior moisture from migrating into the wall cavities, where it can lead to mold growth and other problems.

Typically, the facing is installed on the "warm in winter" side of the wall. Therefore, in most climates, the facing goes on the interior side of the wall frame, so it contacts the backside of the drywall.

Safety Considerations

Always wear tight-fitting breathing protection and safety goggles when working with fiberglass insulation, as it can irritate eyes and airways. For extra comfort, wear long sleeves, pants, and gloves, which will keep the scratchy fibers off your skin where they can cause a rash.

What You'll Need

Equipment / Tools

  • Respirator or filter mask
  • Safety glasses or goggles
  • Staple gun
  • Tape measure
  • Utility knife
  • Work gloves
  • Shop vacuum
  • Long-sleeved shirt and long pants


  • Insulation of your choosing


  1. Purchase Insulation

    To calculate how much rolled or batted insulation to buy, measure floor to ceiling and multiply by the number of between-the-studs spaces you need to fill. That's your total lineage. Measure the distance between the studs; that will determine the width of the insulation you buy. To calculate the number of rolls or batts you need, divide the total lineage by the length of the batt (usually 8 feet) or roll (different lengths are available) you'll be working with.


    Measure the depth of the studs and determine whether it is 2x4 or 2x6. That will make a difference in the R-value you select. Trying to fit R-19 or R-21 into an R-13 space would be difficult and would not result in the R-19 or R-21 value.

  2. Clean Walls

    With the hammer and screwdriver, clean out the wall cavities between the studs. Remove nails, unused wires, and screws. With the shop vacuum, thoroughly clean out the walls, removing spider webs, dust, and debris.

  3. Unroll Insulation

    Unroll the fiberglass insulation or the batts on a clean floor and let them expand.

  4. Trim Insulation

    If you're working from a roll, you can either trim for length with the insulation rolled out on the floor, or you can start with the edge of the roll at the top of the space you're filling, roll down to the bottom, and trim there with a utility knife.

    If you're working with batts, you likely have 8-foot lengths and won't have to trim for length at all.

  5. Push Insulation Into Wall Cavity

    Gently press the insulation into the opening between the wall studs, trimming around electrical outlets.

  6. Staple Insulation Edges

    Snug-fitting insulation will stay put without fastening, but faced insulation is available with stapling flanges—extra paper facing along each side edge that allows you to staple it to the side of the wall stud. Open-faced insulation can't be stapled, so it needs to fit snugly for friction to hold it in place.

Tips For Installing Insulation in Walls

  • Never compress the insulation. While it seems that wouldn't change its effectiveness, in reality, you severely compromise the R-value by removing the air between the fibers.
  • If a roll or batt is too long for a space, it must be trimmed and never folded over itself for optimum performance.
  • When finished, launder your work clothes in a load separate from your regular wash and run the rinse cycle twice.