Insulate ducts to stop ceiling damage

Q Part of the ceiling drywall in my finished basement has water damage, right below the duct that delivers air to the upper two floors. I don’t know the cause but suspect condensation because the problem is primarily in the summer.

When the problem cropped up two years ago, I thought it was a one-time issue. I cut off the damaged drywall and had plumbers and heating and air conditioning folks look at the problem.

The plumbers ruled out a plumbing problem and the HVAC techs were of little help.

Last August, while I was abroad, I had installers put on a new roof with more vents and an attic fan triggered by high temperatures or humidity.

Now that I’m home, I see new damage. I don’t know whether it occurred before or after the new roof.

Will this fix the problem or do I need to cut away lots of drywall to get at the ducts and do some repair on them? A Your new roof and its better ventilation might lower the humidity in your house enough to fix the problem, but it’s more likely that you will also need to insulate the ducts in your basement ceiling.

The condensation is undoubtedly caused by allowing relatively warm, humid air to contact the cold surface of ductwork carrying cool air. It’s just like the sweating that forms on the outside of a glass of ice water on a humid summer day.

An insulation contractor or even a home handyman should be able to help you if you don’t want to tackle the job yourself.

You will need to cut into the ceiling drywall, but only directly under the ducts. If you do it carefully, it might be possible to reinstall the pieces you cut out, minimizing the amount of taping, sanding and even repainting that you need to do.

If you hire a handyman, ask them to do the patching as well as the initial work; it’s a good way to encourage a tidy, waste-minimizing job.

Home centres carry a variety of products designed for insulating ducts.