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Comfortbatt/Rockwool/Roxul and temporary compressibility

I have some framers coming tomorrow and have a basement wall being constructed inside the existing wall so as to insulate inside the stem wall. I'm planning on using rockwool comfortbatt at the bottom of the wall to allow for some breathability of the stem wall.

Will I be able to squeeze the 5.5" comfortbatt through a 3-3.5" wide opening (it will expand to full size, once in the wall)?

It hard to tell if it can compress that much, even intermittently, though I'm guessing so.

Asked by rossn1
Posted May 20, 2018 10:36 AM ET


2 Answers

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Yes they will compress fine. You just have to watch you don't tear them pushing them through.

Answered by Malcolm Taylor
Posted May 20, 2018 5:33 PM ET


Malcolm seems to understand your question, but I'm not sure I do.

The most important question is: Are you planning to install mineral wool batts directly against concrete? If you are, that's not a good idea, since mineral wool batts are air-permeable and vapor-permeable, allowing interior moisture to reach the cold concrete, where the moisture can condense.

It sounds like you want your concrete wall to dry to the interior. That's not a good idea. You don't want to invite the moisture in the concrete to enter your house.

For more information, see How to Insulate a Basement Wall.

Answered by Martin Holladay
Posted May 21, 2018 5:15 AM ET

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