As leaves fall, the insulation goes up


Fall is the perfect time for a particular kind of fashion BTC statement. Call it the buttoned-up look: long pants, long-sleeved shirt buttoned at the neck, maybe a second shirt or sweat shirt over that, work gloves, hat, safety glasses, dust mask.

What event necessitates this excessive wardrobe? Installation of fiberglass insulation. The clothing is one reason cooler weather is the perfect time for this activity -- imagine wearing all that gear in August.

But apart from the clothing, there's nothing very complicated about the installation. The tools are simple, the techniques logical, and the work goes quickly. Even a homeowner who's not otherwise handy can probably put in insulation.

The hardest part of insulating may be figuring out what kind to buy, and how much. And that's not all that hard. Multiply the width by the length of each wall to be insulated and add it all up to determine how many square feet you need. The packages are labeled with how many square feet they'll cover. Try not to buy more than you need, or can use in a short period of time; it's bulky, it doesn't store well (if a roll sits around it could absorb moisture); and it's readily available.

We've noticed that any discussion of R values tends to make people's eyes glaze over. R value, for those of you still awake, indicates a material's resistance to heat loss (or heat gain, in the summer). The higher the R value, the greater the resistance.

But you don't need to know that. All you need to know is how deep the studs or joists are. For 2-by-4s, use R11 or R13. For 2-by-6s, use R19. For 2-by-10s (common in floors and ceilings), use R30. If the space already has insulation (an attic, say, or crawl space), you don't need a vapor barrier. If there's no insulation already, buy batts faced with a kraft paper vapor barrier. Don't fret over the placement of the vapor barrier: It should face the side you're paying good money to heat (and/or to cool). Buy batts the width between studs (narrow) or between ceiling joists (wide). Unless you're simply laying it down over previous insulation, buy batts with flanges, for fastening them to the wood.

There is one subtlety, and it's in how the batts are packaged. They used to come in continuous rolls. Now they also come in strips that are 7 feet 10 inches long, designed to fit perfectly in the stud bays of an 8-foot ceiling. If your ceilings are taller than 8 feet, buy the continuous rolls, or you may have to do a lot of piecing to fill the bays and avoid waste.

Choosing tools is simpler than choosing batts. You'll need an ordinary utility knife with extra blades, a stick or putty knife (to push insulation into crevices) and a heavy staple gun, one that will shoot 3/8 -inch staples. The recommended way to install the batts is to face the vapor barrier toward the heated space and staple the flange to the face of the stud or joist; the flanges overlap so the studs aren't visible.

However, drywall installers hate this method because they believe the paper interferes with the drywall. When we install drywall, we glue and screw it to the studs, to get a tight bond and avoid nail pops -- places where drywall nails pop through the tape and joint compound where two pieces join. So we staple the insulation to the sides of the studs. If you're not concerned about future problems with the drywall, and if you are concerned with saving every bit of energy, you should install it the recommended way.

Here are some things to keep in mind when you're putting the batts in place:

*Insulation should fit in the space snugly, but should not be packed in. Packing it tight will reduce the R value; keep it loose for maximum insulation impact.

*Don't skip the joist bay above the tops of wall studs. Where an interior wall intersects the wall being insulated, we usually insulate the first stud bay on that wall, so air can't find a way to circulate around the insulation.

*Once all the major cavities are filled, pack all remaining crevices with scraps, paying special attention to areas around doors and windows. We also use scraps in the joist bays, so waste is usually not a problem.

*Tuck insulation behind water lines, so they remain on the heated side of the wall. Be careful not to place insulation around a pipe so it juts out past the plane of the wall; it can buckle the drywall.

*Be careful putting insulation around recessed ceiling fixtures; some of them get extremely hot, and insulation shouldn't come too close.

Finally, some cautions about working with insulation:

*Paper-faced insulation is flammable, so you don't want to leave it uncovered too long.

*Insulating is a job best done in one big push. That will reduce mess and cleanup, as well as safety hazards. Try to block out enough time (and recruit enough help) to finish the job in a day, or at least over a weekend.

*Some people are sensitive to the fibers in insulation; they should stay away from the house, or at least from the area, until cleanup is over.

*When you finish insulating, sweep up carefully, let the dust settle for a bit and sweep again. If you have time, do it a third time.

*Don't touch your skin while you're working with insulation. The little fibers can be extremely irritating. No matter what itches, don't scratch it.

*When the job is done, wash all clothing separately from family laundry.

This may not sound like much fun; all we promised was that it would be relatively easy to do. At least, since the batts are usually brightly colored, you have the satisfaction of being able to see exactly how much you've accomplished.

Mr. Johnson is a Baltimore construction manager. Ms. Menzie is a feature writer for The Sun.

If you have questions, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N.

Calvert St. Baltimore 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.

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