What materials are best for pipe insulation?

Dear Angie: I own a very old house (built in 1780) with a field-rock foundation. When I bought the house, my basement was finished. However, last month, I had to remove all finishing walls and insulation because of problems with mold and fungus. Now, my walls are totally bare and the cold and hot water pipes and the drain pipes are running right along the exterior basement walls. My handyman is concerned that the pipes may freeze in the winter if we don’t insulate them.

What material will be best to use for pipe insulation to ensure these pipes will not freeze in the winter? Can we use the same insulation material for the water pipes and for the drain pipes? What would be the correct type of insulation material and its R-rating? — Teresa S., Newton, Mass.

Dear Teresa: Your handyman is correct. Plumbing along exterior walls is prone to freezing, especially in an area that is not heated. Assuming you've addressed the cause of the moisture and mold in your basement, the next step is to insulate those pipes. R-value indicates insulation's resistance to air flow, so the higher the R-value, the more effective the insulation. In Mass., the minimum R-value for basement walls is R-10.

Most home improvement stores carry R-4 foam pipe insulation, which should be wrapped around your water pipes. It's important to pick the correct size for your pipes (either ½ or ¾ of an inch). Be sure to cover the entire pipe, including elbows and turns, or freezing can still occur. Unless there is a place in your drain lines where water stands, they are unlikely to freeze. A professional can tell you for sure whether or not yours needs insulated.

A long term solution would be to insulate your basement walls with a closed cell foam insulation with an R-value of 7 per inch. Adding 2 inches of thickness would yield an R-14 installed value. You'll need to add a fire retardant coating over the foam insulation. This would insulate your pipes as well, eliminating the need for the foam pipe wrap. This can be a lot of work for the inexperienced homeowner, though, so I recommend calling at least three insulation companies for estimates. You might find that they are able to do a better job for a comparable price of you doing it on your own.

Now is a good time to add insulation to your home. Check to be sure you qualify, but federal tax credits are available for 30 percent of the cost of the materials, up to $1,500. Some utility providers also offer extensive rebates for homeowners who add insulation.


During cold snap had water leaks from the bare water pipes in a 3rd floor attic. Will foam insulation wrap be sufficient to protect from freezing? Live in Gulf Shores, AL right on Gulf of Mexico. Thanks

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