How to Install Insulation in Existing Walls

Installing insulation in existing walls might sound intimidating and time consuming, but according to, “Thanks to modern equipment and advanced loose-fill insulating materials, installing insulation between walls that are already finished is something that can be accomplished in just a few hours” for a professional, or an experienced “do-it-yourselfer”. However, if you aren’t an experienced “do-it-yourselfer”, and you don’t want to hire someone to do it for you, you can accomplish this task yourself just by simply following these directions.

Using blown insulation is the best method for adding insulation in an existing wall…

  • Insulation is projected into the cavity through a hole until the cavity is completely filled. The most challenging aspect of this job is
  • When using this method, you have to make sure that the cavity is completely filled with insulation. In areas where plumbing pipes or ductwork may be involved,
  • You may need to make several holes to ensure that the cavity can be filled entirely
  • This method is easiest to perform from outside of the house, so you will need to remove your siding


  • You should wear eye goggles, work gloves, a long-sleeved shirt and a NIOSH-approved breathing respirator
  • You also need to turn off the electricity to the circuits in the wall you’ll be working with
  • All blowers are different, so be sure to read the instructions for loading the hopper and using the blower
  • Outside the house: measure four feet from the floor line and start removing strips of siding, working at four-foot intervals; use the pry bar and hammer to loosen and remove siding made out of wood; separate the seam and run a zip tool along vinyl siding

Tools Needed: pry bar (wood siding), hammer, zip tool (vinyl siding)

  • Find studs using the stud finder, and mark the location of studs so you know where you can drill access holes

Tools Needed: stud finder

  • Cut access holes between studs by using a drill with a hole saw or a saber saw; holes should be a little bigger than the nozzle of the blower

Tools Needed: drill with bits and hole saw or saber saw

  • Put blower’s nozzle into access hole; turn machine on; fill the cavity with insulation, then move to the next access hole (if necessary).

Tools Needed: blower equipment, loose-fill insulation

  • After you’ve finished filling at an access hole, plug the hole with the appropriate sized plastic plug; you can use glue to help keep the plug in place; replace the siding

Tools Needed: plastic plugs

  • Move on to the next four-foot span of siding and repeat

For more information on insulating existing walls, check out this article on 

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