Adding insulation won’t drive you batty

: I have an older house and I want to insulate the garage. The walls are unfinished, so I think I can easily add insulation. What kind of insulation do I need and how should it be installed?

A: It’s a great idea to add insulation to your walls. You didn’t mention whether you use your garage for a living space or if you just want to make your garage more efficient and add a little sound absorption to it. Regardless, fiberglass batts are for you.

The batts are fairly easy to install, but the work is slow and quite itchy. Batts come in different R-values, which denote the level of thermal resistance. The higher the R-value, the better it insulates. So, insulation with a higher R-value is more expensive, of course.

Since your walls have limited space for insulation, buy the best that your budget allows. For attics that have plenty of space, you can usually buy the cheaper insulation and just add more layers of it.

As you get ready to install insulation, remember to put on proper protective gear. You must wear long sleeves and long pants, along with gloves and a hat. You also must protect your lungs with a breathing mask rated for fiberglass insulation, and you’d better wear goggles to protect your eyes. This may sound extreme, but getting fiberglass dust in your eyes and lungs is both uncomfortable and unhealthy.

There also is “low-itch” insulation available, but you can expect to pay a premium for it.

Insulation batts come with either a paper face on one side or unfaced. The paper facing has flaps and allows the batts to be stapled to the studs so the batts won’t fall out. Unfaced batts just push into the wall cavity and fit snugly in place. Although it’s rare, they can fall out if you don’t finish the wall.

The batts come in widths to fit into both 16-inch or 24-inch on-center stud bays, and you can buy precut lengths to fit standard wall heights. Batts also come in a continuous roll or are cut into 4-foot lengths. The thickness starts at 31/2 inches for 2×4 framing and goes up to 12 inches thick for attic spaces.

After you’ve dressed for the job, start at the top of the stud bay and push the insulation to the point where it compresses. The idea is to fill the entire bay with insulation.

If you are using the paper-backed batts, staple the flaps to the wall studs. If you are using the unfaced batts, friction does a nice job of holding it in place.

If you need to cut a batt to length, do that a half-inch too long so that there will be no voids. Use a sharp blade in a utility knife and slice through it. If you have long lengths to cut, you can lay a straightedge on the batt, push down on it (compressing the batt) and cut it easily.

Plan on running into obstacles, such as electrical outlets, wiring and plumbing. You will see the electrical cables near the base of the stud bay. Instead of laying the insulation over the front of the cable (which would leave a void behind it), split the insulation batt so that half the insulation is in front of the cable and half is behind. This is done by tearing the batt in half, starting at the bottom and going as high as the cable.

You can do the same thing for pipes, although in colder climates the insulation is usually pushed behind the pipe to allow heat from the house to warm the pipe.

For electrical outlets, run the blade around the outside of the box to guide the cut, but don’t cut so deeply that you nick the wires (it’s a good idea to turn the power off when doing this).

When you’re done, you can either finish off the walls, or just sit back and marvel at how lovely unfaced insulation can be.

Michael D. Klimek is a licensed contractor and president of Pro Handyman Corp. Questions may be sent by e-mail to: questions@pro-handyman.com. Or, mail to: P.O. Box 96761, Las Vegas, NV 89193. His Web address is: www.pro-handyman.com.