Repairing insulation damaged by squirrels

Q. My house has cathedral ceilings with 2-by-12-inch rafters to which the builder nailed 2-inch-high sleepers, bringing the effective depth for insulation to 13⁵ / ₈ inches. I had wanted to use 12 inches of insulation, leaving enough of a gap above the insulation for airflow. But then I realized the 12-inch insulation would expand to fill the whole space, so I went with batting 9 inches thick. Since then, squirrels have gotten between some of the rafters and “squirreled” up some of the insulation. I wish to add additional insulation, perhaps fill the entire cavity by blowing some in. I heard that leaving an air space is no longer important. Is this correct?

Reston

A. It’s true that many building codes now permit fully insulated cathedral ceilings without an air gap, but you can’t just stuff in more insulation and meet code. There’s too much risk that moisture-laden air will sneak through gaps in the ceiling, move through the insulation and condense on the underside of the roof sheathing, eventually causing it to rot.

To prevent moist air from meeting a surface cold enough to allow condensation, you need to either keep the air channels or coat the underside of the roof sheathing with spray-on foam insulation that blocks airflow. To install that foam, you would need to remove the drywall or other ceiling material and take down the existing insulation. You could then fill the cavities between rafters entirely with foam. Or, to save money, you could use a thin layer of foam and then install fiberglass or cellulose below that. Either way, the total insulation value needs to be at least R-38 for your area. And you need a ceiling finish that blocks airflow as much as possible. Painted drywall works well. If you want a board ceiling, install drywall first and then cover it with the wood.

If you don’t want to take down the ceiling, you can add rigid foam board insulation above the roof sheathing. But that means taking off the roofing and then installing a new roof. If you need a new roof anyway, it’s a great option. Otherwise, it’s probably not cost-effective.

(Scott Barbour/GETTY IMAGES) - Squirrels have damaged a homeowner’s rafters.

I bought a leather sofa three years ago, but now it is sagging so much that I am developing a backache. I do not want to throw it away, as it’s in good condition. Can I repair it?

Falls Church

If the seat cushions are removable, try slipping stiff supports under them. A product called Seat Savers from Carol Wright Gifts (about $20; www.carolwrightgifts.com) is made for the purpose. You can trim these panels to size with scissors. Or you could make something similar from a sheet of quarter-inch-thick plywood that’s a little smaller than the couch seat. Wrap the plywood in a thick piece of fabric so it doesn’t cut into the upholstery.

If that doesn’t work or if the cushions aren’t removable, tip over the couch and see if you can spot anything that’s broken or bent. To inspect, you might need to cut away the fabric dust cover on the bottom of the couch, but you can easily staple on replacement fabric when you’re done. It’s not feasible to replace a broken frame piece, but you might be able to screw a new, straight piece alongside one that’s cracked or bent. If you find zigzag springs that are loose, stiffen them by stapling or nailing electrical cord (like that on a lamp) to the frame in line with the springs. Then push the cord under and over the springs to limit how much they can flex. Or you might find coil springs that are tied together in most places but need a few pieces of replacement cord. Or sagging webbing could be part of the problem; you can stretch this as tight as you can and restaple the ends.

In addition to these tricks, also consider setting out a few decorative throw pillows. You might find that stuffing one behind your back as you sit down makes all the difference in comfort.

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The Checklist Read Jeanne Huber’s roundup of home-improvement tasks for September, such as decluttering the basement.