Interior Walls: Insulation is a Sound Decision
Insulate interior walls? You bet. It's a sound decision. Literally.
An interior wall packed with insulation will block sounds--loud sounds, objectionable sounds, embarrassing sounds--that travel between bedrooms, toilets, kitchens, rec rooms and living rooms.
What's more, sound insulation can greatly assist the overall climate control in your home by keeping heat in or out of rooms as you desire.
And chances are, if you are in an old house, it was built before anybody thought of filling the interior walls with spun fiberglass for sound insulation.
Old House Walls Paper Thin?
You may complain that the walls in your old house are "paper-thin," but in all likelihood, they are the same thickness as everyone else's, 4½ inches--that's 3½ inches for the 2x4 stud sandwiched between sheets of ½-inch drywall.
If your walls are old lathe-and-plaster, they will be thicker, and also will block sound a little better than drywall.
And if you have a really old house, the studs might be a true 4 inches wide, making the old home's paper-thin walls even thicker. But if there is nothing but air inside them, the walls are still going to let those unpleasant or private sounds pass through them as if they were paper-thin.
Sound Insulation Room by Room?
You could quiet those walls by having sound insulation--either fiber or foam--blown in between the studs. But this is labor intensive and requires drilling holes in the walls that need to be repaired. Of course, if your walls are lathe and plaster, you don't want to rip them out. You may have little choice but to have the sound insulation blown in, or suffer with the noises.
However, if sound suppression isn't an immediate priority and you are dealing with drywall, then any time you are doing a project in a room requiring some disruption of the wall, rip out the wall. An extreme measure, you say? Not necessarily. If your project includes some drywall repair, then you already have the dust and refinishing to contend with anyway. You can throw some batts of R-11 insulation between the studs, and install new drywall. It's not much more work to tape and mud a whole wall as a smaller section. If you are doing the work yourself, it doesn't cost much either.
Just make sure when installing the insulation that the insulation is snug in the cavity, including around electrical boxes. Air spaces will let the sound penetrate the wall. And make sure the insulation is dry before you install it; never use insulation that's been stored outside.
There isn't a happy solution to interior noise problems. But if you are the consummate remodeler, you may have opportunities arise from time to time to quiet your rooms without stifling their inhabitants.
Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.