Have an old house without insulation? Don’t despair. You can add insulation to your exterior walls—without the cost and inconvenience of removing your existing drywall—by blowing cellulose fibers between your wall studs.

Cellulose is a popular blown-in insulation material because its small particles fill in the nooks, crannies, and irregular areas of wall space quite well. It is also considered by many to be a “green” material, as it is composed of up to 75 percent recycled newsprint and does not contain formaldehyde, which can release harmful vapors into the air.

Another bonus is the fact that cellulose insulation can be added to walls by the ambitious do-it-yourselfer. Equipment for the job can be rented at many home improvement centers. Always wear safety goggles and a mask or respirator when working with this material.

1) Use a stud finder to locate studs in the wall. With a hole saw, cut a small hole (between 2 and 3 inches wide) between two studs and near the top of the wall, and place the cut portion aside—you will reattach this later. Repeat this step between each pair of studs.

2) Thread the blower hose into the first hole, and point the nozzle down deep into the wall cavity. Wrap a rag around the hose where it meets the wall to form a seal.

3) While you hold onto the hose, have a friend turn on the blower. Pull the hose back as the cavity fills. Ask your helper to stop the machine when you feel resistance and can no longer insert insulation.

4) Repeat steps 2 and 3, filling up the remaining wall cavities.

5) Once you have finished, reinsert the drywall cutouts and patch up and paint over the holes.