Home Improvement

Ask the Remodeler: The best insulation for keeping out moisture

Thinking about adding spray foam insulation? How long will you need to be out of the house? Continue reading at realestate.boston.com.

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Q. In a previous article, you discussed the use of Icynene and open- and closed-cell insulation (“Ask the Remodeler: A home with a mansard roof needs insulation. But what kind?’’ May 25). We got two quotes for air or water sealing from Mass Save and a professional spray-insulation installer for the top of our basement foundation. The professional spray-insulation installer recommended open-cell because of its water-proofing and air-sealing properties. However, he stated that we would need to be out of the house for 24 to 48 hours due to the gas it releases as it cures. Mass Save recommended closed-cell air sealing but made no mention of leaving the house while it cures. Open-cell was two times the cost of closed-cell.

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The installation is in a heated, finished basement that has had three burst pipes in the past few years during typical February quick freezes below 20 degrees. They happened even though we keep the heat at 55 degrees. I was told to wrap the hot water pipes over the foundation wall, install batts of unfaced insulation around the pipes that lead to the exterior, and turn the heat up to 65 degrees in the winter.

What should we do, and more important, what would you suggest that wouldn’t require us to be out of the home for a day or two? The restriction is a deal-breaker. My wife and I are concerned about toxic gases and leaving our home for that period of time.

J.R.

A. While you can use open-cell around the top of the foundation wall, it is definitely not the best for stopping moisture or air sealing. Closed-cell is far superior for both categories. (I am not sure if it is a typo, but the closed-cell should cost twice as much as the open-cell. Not the other way around.)

Regarding the time you must be out of the house, this is something you should discuss with your installer. There is a big difference in the formulas that are used for installing Icynene. The formula that our installer uses allows for a one-hour reentry with proper ventilation, meaning open windows and fans where possible. To help in your planning, ask your installer for the MSDS (material safety data sheet). All installers have access to this.

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One key to keeping those pipes from freezing is to use the closed-cell (which has a higher R-value) and make sure it gets around the back side of the pipes, closest to the exterior. You actually want to keep them exposed to the inside temperatures as much as possible while sealing them from behind.

Mark Philben is the project development manager at Charlie Allen Renovations in Cambridge. Send your questions to [email protected]. Questions are subject to editing. Subscribe to the Globe’s free real estate newsletter — our weekly digest on buying, selling, and design — at pages.email.bostonglobe.com/AddressSignUp. Follow us on Facebook, Instagram, and Twitter @globehomes.

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