How to Install Insulation in Open Walls

By
Lee Wallender
Lee Wallender
Lee Wallender

Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.

Learn more about The Spruce's Editorial Process
Updated on 03/08/24
Reviewed by
Kelly Bacon
Kelly Bacon
Reviewed by Kelly Bacon
Kelly Bacon is a licensed general contractor with over 40 years of experience in construction, home building and remodeling, and commercial building. He is a member of The Spruce Home Improvement Review Board.
Learn more about The Spruce's Review Board
A person installing insulation in between wall studs.

The Spruce / Kevin Norris

In This Article
Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 1 - 2 hrs
  • Yield: Insulated wall
  • 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.

What Is R-Value?

The R-value for insulation measures 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.

Before You Begin

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, and the depth of the studs will affect which R-value you select. Measure the space between the studs, which are usually spaced 16 or 24 inches apart, to choose which width of insulation to buy. For the depth of studs, determine whether it is 2x4 or 2x6. 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.

Which R-Value Should I Choose?

Choosing R-value depends on where you live, what type of heating system you have, as well as whether you're insulating for energy efficiency or noise reduction. The US Department of Energy's zone map provides corresponding R-values to help homeowners determine minimum insulation values.

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.

Use unfaced insulation for interior walls or in rooms where moisture and humidity are not a problem. If using unfaced insulation on exterior walls, it can be left exposed, or you can add a separate vapor barrier, such as polyethylene or polypropylene, for moisture prevention.

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

Materials

  • Insulation of your choosing

Instructions

Various tools laying on a wood floor.

The Spruce / Kevin Norris

How to Install Insulation in Open Walls

  1. 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.

    A person removing a screw from a wall stud.

    The Spruce / Kevin Norris

  2. Unroll Insulation

    Unroll the fiberglass insulation or the batts on a clean floor and let them expand. The insulation will expand on its own when as soon as it's unpackaged. 

    A person unrolling insulation.

    The Spruce / Kevin Norris

  3. 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.

    A person using a utility knife to trim insulation.

    The Spruce / Kevin Norris

  4. Push Insulation Into Wall Cavity

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

    For faced insulation, the paper side should face the interior of the room, not toward the outside of the house. For unfaced insulation, you can add a vapor barrier if used on exterior walls.

    A person installing insulation inbetween wall studs.

    The Spruce / Kevin Norris

  5. 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.

    A person securing insulation into a wall with a staple gun.

    The Spruce / Kevin Norris

When to Call a Professional

If the scope of your project is large, involves removing old insulation, and will require other repairs, you might want to call a professional. Replacing and disposing of existing insulation is a messy and hazardous job and may expose other issues that require repairs. Seek a professional if the insulation area contains hazardous materials like mold, asbestos, lead, or an animal infestation for safe removal.

FAQ
  • Can I use loose fill to insulate walls?

    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.

  • What types of insulation can I use for a DIY project?

    Consider where you’re installing insulation before choosing the correct material for the space. The type of insulation used for a project also depends on the age of the home in addition to where it will be installed. For new construction, options include materials like structural insulated panels (SIPs), insulating concrete forms (ICFs), and concrete block insulation, which are professionally installed. For existing homes, insulation materials are DIY-friendly and include batts, rolls, radiant barriers, loose-fill, blown-in, spray foam, rigid foam, and recycled insulation materials.

  • What are some common mistakes when installing insulation in walls?

    Keep these tips in mind before you start your insulation project. First, 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. Second, if a roll or batt is too long for a space, it must be trimmed and never folded over itself for optimum performance. Finally, when finished, launder your work clothes in a load separate from your regular wash and run the rinse cycle twice.

  • Is installing insulation in open walls a difficult DIY project?

    To install insulation in open walls, using roll and batt insulation with facing is the most straightforward to work with for a DIYer as it’s easy to cut, fit in walls, and the least messy to handle. If using unfaced insulation, it is more difficult to secure in walls and may require more steps like adding a separate vapor barrier. Call a professional if the insulation area needs old insulation removed, contains hazardous materials, or requires additional repairs.