Safety Tip

Improving your home is more satisfying when you stay healthy enough to enjoy it.

You’re Here: Home » Home Insulation  »  Insulation Projects  »  By Room  »  Basement

Basement Insulation

Proper basement insulation is important because an uninsulated basement can account for as much as 25% or more of a home's total heat loss. Whether your basement is and will remain unfinished, be used for storage, or be finished for use as living space, make sure that it is properly insulated with the right amount and kind of insulation.

Unframed, exterior basement walls should be insulated with blanket insulation, which can be installed horizontally or vertically. Typically, the blanket is held against the sill plate at the top of the basement wall with furring strips. In addition to the furring strips, you will need patch tape, and depending on the installation method you choose, possibly a Hilti-type gun and special fasteners for driving into concrete or cinder blocks. If you need a Hilti-type gun, be sure you become completely familiar with its operation before using it.

It's a good idea to wear a work helmet when you're installing basement insulation. You certainly want to avoid injuring yourself on exposed framing members such as ceiling and floor joists, exposed nails and other hazards.


How to Install Basement Insulation on Unframed Walls

Horizontal Installation

  1. Seal around all penetrations in band joists. Any walls that leak water must be repaired before insulating.
  2. Pre-drill an ample supply of 1x2 furring strips.
  3. Measure the length of insulation you'll need for the full wall and cut it on the unfaced side.
  4. Grip the insulation by the flange, and with the faced side toward you, position it against the sill plate at the top of the basement wall. Then position a furring strip and nail through the furring and the flange to the sill plate to secure the insulation. Whenever possible, pull the insulation behind any ductwork, plumbing, or electrical that may lie along the walls. Otherwise, carefully cut and fit the blanket around obstructions.
  5. When you cover the full wall, you'll need to attach a second length of the blanket to the lower edge of the first one. If you have cut a piece to fit and there is no flange, create one by pulling back the insulation. Overlap the flanges of the top and bottom pieces so that the insulation butts together tightly. Then, staple through the flange to hold the pieces together. An alternate method is to attach furring strips to the wall at the mid-point and bottom of the wall. Then staple the blanket flange to the furring strips.
  6. To give the insulation a finished look, tape over all joints, seams and stapled edges with 3-inch wide, white vinyl patch tape.
  7. Cut small pieces of batt insulation to fit against the header joists and push them into place between each floor joist.

Vertical Installation

  1. Seal around all penetrations in band joists. Any walls that leak water must be repaired before insulating.
  2. Cut lengths of insulation a few inches longer than the height of the walls.
  3. Attach the blanket to the wall using furring strips or a Hilti-type gun to drive fasteners into the concrete or cinder blocks. Fit adjacent blankets tightly together.
  4. Trim the bottom of the insulation flush with the floor.
  5. To give the insulation a finished look, tape over all joints and with 3"-wide, white vinyl patch tape.

How to Install Insulation In Ceilings

  1. Seal around all penetrations in band joists. Any walls that leak water must be repaired before insulating.
  2. Caulk where wiring runs through the ceiling joists and around the top of the wall.
  3. Gently press the insulation between the joists. If you're using unfaced batts or rolls, allow friction to hold the insulation in place (called "friction fit method"). If a polyethylene vapor retarder is used, staple it across the unfaced batts. Check to make sure there are no openings where moisture can escape. If you're using faced insulation, install it with the vapor retarder positioned down toward the room. Hold the insulation up with one hand, while stapling the flange on both sides every 6" - 8" with the other hand. Leave a little extra on each end to cover the top plate of the outside wall.
    In attic installations, make sure the insulation completely covers the top plate of the outside wall at the end of each joist run. However, it should not block the flow of air from the eave vents. If necessary, install baffles at the inside of eaves.
  4. Expand the insulation to its full thickness in the joist cavity to insure complete coverage. Avoid compressing the insulation material, because compression will reduce its R-value.

Related Products

JM Spider® Custom Insulation System


JM Spider® custom insulation sprays-in filling all gaps and voids in your walls, significantly improving energy efficiency, sound control and family comfort.

ComfortTherm® Batts and Rolls


ComfortTherm® insulation is a lightweight, thermal and acoustical insulation made of long, resilient glass fibers bonded with an acrylic thermosetting Formaldehyde-free™ binder.

Kraft-Faced Batts and Rolls


JM's Kraft-Faced Batts & Rolls are made of naturally white, Formaldehyde-free™ fiber glass, reducing environmental concerns including the risks of poor indoor air quality and the effects of manufacturing on the environment.

Unfaced Batts and Rolls


JM's Unfaced Insulation is a lightweight thermal and acoustical fiber glass insulation made of long, resilient glass fibers bonded with an acrylic thermosetting resin made without formaldehyde.

How to Install Insulation in a Finished Basement

Installation Tips

Finished basements are insulated like any other room in your house.

How to Install Insulation in Interior Walls

  1. To install in interior walls for good sound control, apply caulk between the top plates and at the bottom plate and floor. You should apply sealants or caulks only to clean, dry, oil-free surfaces. Smooth caulking with your fingertip or a putty knife.
  2. If you are using faced batts, place the batts into the wall cavity and staple the flanges of the batts to the inside or the face of the studs about every 12". If you are using unfaced batts, place the insulation into the cavity, making sure that it is the correct size and fits snugly at the sides and ends and does not protrude in the back.
  3. If the insulation is too long, cut it to fit properly. Don't double it over or compress it. Use a sharp utility knife and straightedge. Cut batts on a smooth, flat surface, and cut them about 1" larger than the framing cavity. If the material is too short, cut a piece to size to fill the gap.
  4. Fill in any narrow gaps between joists by forcing pieces of unfaced insulation into the gaps with a screwdriver or putty knife.

Related Products

ComfortTherm® Batts and Rolls


ComfortTherm® insulation is a lightweight, thermal and acoustical insulation made of long, resilient glass fibers bonded with an acrylic thermosetting Formaldehyde-free™ binder.

EasyFit® Batt Insulation


JM's EasyFit® Formaldehyde-free™ insulation is available unfaced or with kraft facing, and has vertical perforations for fitting non-standard wall cavities.

Kraft-Faced Batts and Rolls


JM's Kraft-Faced Batts & Rolls are made of naturally white, Formaldehyde-free™ fiber glass, reducing environmental concerns including the risks of poor indoor air quality and the effects of manufacturing on the environment.

Unfaced Batts and Rolls


JM's Unfaced Insulation is a lightweight thermal and acoustical fiber glass insulation made of long, resilient glass fibers bonded with an acrylic thermosetting resin made without formaldehyde.

How to Install Insulation in Exterior Walls

Insulation should be installed in all exterior walls that separate conditioned spaces from unconditioned spaces, including knee walls and basement walls.

  1. If you are using faced batts, place the batts into the wall cavity and staple the flanges of the batts to the inside or face of the studs about every 12 inches. Kraft facing must not be left exposed. It must be covered with gypsum board or another approved interior finish. Where an exposed application is required, use FSK-25 flame-resistant faced insulation. If you are using unfaced batts, place the insulation into the cavity, making sure that it is the correct size and fits snugly at the sides and ends and does not protrude in the back.
  2. If the insulation is too long, cut it to fit properly. Don't double it over or compress it. Use a sharp utility knife and straightedge. Cut batts on a smooth, flat surface, and cut them about 1" larger than the framing cavity. If the material is too short, cut a piece to size to fill the gap.
  3. Fill in any narrow gaps between joists by forcing pieces of unfaced insulation into the gaps with a screwdriver or putty knife.
  4. To control air leakage, apply caulk or foam sealants around openings like window and door frames and any openings where wires or pipes go through the exterior wall.

To apply a vapor retarder:

  1. To apply the poly film, start at the top plate in one corner of the room.
  2. Pull the film tight and staple at least every 12 inches.
  3. Drive staples at the center of every stud and around openings, working around the room.
  4. Overlap the sheets by one complete cavity to minimize leakage. Then staple evenly through, fastening both sheets to the studs at one- to two-foot intervals.
  5. Pull the film tight along the sole plate and staple in the same manner, making sure the staples are driven flat, flush to the stud surface.
  6. Trim out the poly from over windows, doors and electrical boxes.

NOTE: In areas of the country where vapor retarders are not required, bathrooms would require unfaced insulation and no poly film covering to allow moisture to escape.

Related Products

JM Spider® Custom Insulation System


JM Spider® custom insulation sprays-in filling all gaps and voids in your walls, significantly improving energy efficiency, sound control and family comfort.

ComfortTherm® Batts and Rolls


ComfortTherm® insulation is a lightweight, thermal and acoustical insulation made of long, resilient glass fibers bonded with an acrylic thermosetting Formaldehyde-free™ binder.

EasyFit® Batt Insulation


JM's EasyFit® Formaldehyde-free™ insulation is available unfaced or with kraft facing, and has vertical perforations for fitting non-standard wall cavities.

Kraft-Faced Batts and Rolls


JM's Kraft-Faced Batts & Rolls are made of naturally white, Formaldehyde-free™ fiber glass, reducing environmental concerns including the risks of poor indoor air quality and the effects of manufacturing on the environment.

Unfaced Batts and Rolls


JM's Unfaced Insulation is a lightweight thermal and acoustical fiber glass insulation made of long, resilient glass fibers bonded with an acrylic thermosetting resin made without formaldehyde.

Copyright ©2014, Johns Manville, Inc. All Rights Reserved. Global Sites | SpecJM.com | Site Map | News Archives
Industry Resources | Privacy Policy | Legal Notices
Product & Sales Information: (800) 654-3103