More in Insulation

Insulation Above a Drop Ceiling

What to do when the plaster ceiling is hidden under a suspended one

Ask This Old House Crew
Photo by Matt Kalinowski

At the back of our 130-year-old house there's a flat-roofed addition that contains the laundry room and kitchen. These rooms get very cold in the winter because there is no insulation in the 2x6 ceiling joists. To complicate matters, the original ceiling surface is plaster concealed by a suspended ceiling. I want a warm house. What should I do?
— Genia, Belleville, IL


Tom Silva replies: I'd start by getting rid of the suspended ceiling. It doesn't suit the age of your house, and it was probably installed either to cover up damaged plaster or in a misguided effort to provide some thermal comfort. Then I'd contact an insulation contractor who specializes in spraying polyurethane foam insulation. By using foam, you won't have to worry about venting the flat roof. And you'll get a lot of insulating value into your shallow ceiling cavities. It might be possible for the contractor to spray foam through holes drilled in the plaster. But frankly I think I'd be more inclined to remove the plaster, insulate with foam, and then replaster or cover the ceiling with drywall.


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