To add insulation easily to your home, you can rent a hopper from your local hardware store and blow cellulose insulation in the cavity between the interior and exterior walls. A hopper breaks apart the fibres of insulation and propels it through a hose that you insert between your walls.
Find the studs behind the wall using a stud finder. Mark the locations of each stud with a pencil.
Cut a hole in the wall with the hole saw; make the hole about three inches wide and cut it near the top of the wall. Save the piece you cut out so you can use it later to patch the hole.
Insert the hose from the hopper into the hole you just cut. Point the hose downwards inside the wall cavity. Wrap a rag around the hose to plug up any space between the hose and the hole so insulation won't blow out. Ask your friend to turn on the hopper while you hold the hose.
Cut a hole in the same manner between each wall stud and fill each cavity with insulation as you did with the first hole.
Patch each hole when you are finished. Replace the piece you cut and paste it in place with using drywall compound and the putty knife. Sand the compound when it dries.