How to Install Insulation Under a House

Beau Keyes

Insulation placed under the house in a crawlspace improves the overall quality of the floor temperature while also helping to reduce the chances for drafts. Due to the cramped nature of many crawlspaces, this is not an easy installation to do after the home is built, but it is still possible.

Standard insulation sold at any home improvement or hardware store works for this, and all other materials needed are available there also. Having an assistant is helpful.

  1. Inspect the crawlspace with a flashlight to make sure it is clean and dry, and remove any prior insulation. Be sure to check for moisture damage, wood rot or insects that indicate that the floor above needs repairs.

  2. Determine the amount of insulation needed to insulate between the crawlspace joists. Add 5 percent to your measurements to allow for waste or incorrect measurements.

  3. Roll out some of the insulation and pull it down into the crawlspace. Have someone outside feed you more so that it can be easily placed under the home. Orient the insulation so that the paper side faces down into the crawlspace and the bare insulation faces up against the subfloor.

  4. Lift and install the strips of insulation between the floor joists. Start at the farthest wall from the crawlspace exit and work back. Staple the extending flaps of the paper backing to the stud edges on both sides approximately every six inches. This will hold the insulation in place while you hang the rest. Cut excess to fit using a utility knife.

  5. Attach metal insulation hangers to the edge of one stud and onto another. This will act as a support bar to help hold the insulation in place and take some of the pressure off the staples and paper. They are designed to be the exact width between two standard floor joists. Install by nailing the ends flush with the stud using a hammer. Apply these every five or six feet, across the length of the joists.

  6. Tip

    It is best to have an assistant to help feed you insulation. An extra set of hands to help hold the insulation in place prior to stapling is also recommended.


    Wear gloves, long pants and sleeves when working under the house to protect your skin from irritation from the insulation.

    Eye protection and a face mask are important to protect your eyes from falling debris while on your back during the installation, and to help avoid breathing in dust or contaminants.