Real estate

ASK THE CARPENTER

Adding insulation? Do this first.

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Heat is lost vertically primarily, but air leaks are more detrimental.

Q. I’ve recently had a home-energy audit sponsored through our local electricity supplier. They recommended additional insulation in my two attic areas (main and in an addition) — blown-in, loose-fill cellulose.

Years ago, I’d insulated my main attic incompletely (leaving 30 percent untouched because it was difficult to access). The addition was fully insulated. Both attic areas were insulated to R-19 (then the recommended R value for those areas), using paper-backed fiberglass batts. The audit recommends R-30.

I understood attic heat loss to be primarily vertical, through roofs. Can the goal of “tightly insulated” be overzealous, not allowing a space to breathe? Should I add loose cellulose on top of batted fiberglass?

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KINGSTON OLDIE

A. Heat is lost vertically primarily, but air leaks are more detrimental. Adding cellulose over fiberglass batts is a good idea, and as a contractor, I would not remove insulation to add more. This would cost you more money and, honestly, is not needed unless you have water damage or rodent problems.

Avoid covering recessed can lights unless they are “IC rated” for contact with insulation. It’s safer to build a small enclosure with hardware cloth, ridged insulation, or plywood to keep loose insulation away from lights and bathroom exhaust fans.

The important message here is to seal all air leaks prior to adding insulation. No one ever wants to do this because it takes time and energy, but it’s a task well worth undertaking.

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The insulation contractor will tell you that cellulose blocks pretty well, which is true, but you should never insulate (with any type of insulation except spray foam) without air sealing your top plates first. Air sealing can be done with expanding spray foam. Focus on all penetrations from the attic to the floors below. These include, but are not limited to, wire, pipe, and flue penetrations; around chimneys, soffits, and other blocked framing areas; stairway slants; and between studs on balloon -framed (older) homes.

TIP: To locate air leaks in an attic with fiberglass insulation, look for dark in the insulation, which indicates air filtration. Lift the fiberglass and look for the cause.

You mention your concern about your attics breathing. I assume you mean loss of ventilation space. You do not want to pack the insulation so tight that it blocks your ventilation either at the soffit or ridge. Use cardboard or rigid-foam baffles to keep soffit vents open.

Q. I have hardwood floors throughout my house, which is about 80 years old. The floors are finished with several coats of polyurethane. Traffic wear has caused several bare spots that really stand out. I have been led to believe that floors like mine are impossible to patch because the fix will stand out like a sore thumb. Is this correct?

JACK CROSS, Wellesley

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A. Those patches would stand out. Why not sand everything and refinish? This means bringing the entire floor surface down to, and slightly past, your wear spots and then finishing the entire floor.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @globeaddress or @robertrobillard.