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Water-resistant insulation

We are rebuilding many small buildings (Not Houses) that were flood damaged by Hurricane Irma and have a small probability of flooding again. They are 2"x4" framed walls, sheathed with 1/2" plywood, covered with #15 building paper or house wrap and sided with vinyl or cement board. Remediation work included removing all wet drywall and fiberglass insulation, cleaning and disinfecting the wall cavity, and drying the framing lumber and sheathing to a moisture content of 8% or less. The flooding was short duration (Less than 24 hours) and was uncontaminated lake water so the framing, sheathing, and siding were undamaged. When we rebuild the walls what insulation would you recommend? We have considered closed cell spray foam, closed cell block foam, and rock wool bats. If we use a non porous insulation and a water proof wall covering (PVC trim board, etc.) would it eliminate the need to tear out the wall covering and insulation if another clean water flood occurred? Would a wall assembly like this dry to the outside or should we still open the wall. Thanks for your opinion.

Asked by Anthony Swoope
Posted Feb 14, 2018 10:34 AM ET
Edited Feb 14, 2018 2:05 PM ET


4 Answers

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It's hard to predict how much of the wall you'll have to throw away after the next flood. As you might guess, the biggest variable is the number of hours that the flood stays high, not the type of insulation you choose.

If the flooding lasts a while, everything's going to have to go in the dumpster. While closed-cell spray foam wouldn't be hurt by floodwaters, the closed-cell spray foam would inhibit drying, and might have to be removed for that reason.

I don't think it matters much what insulation you use.

Answered by Martin Holladay
Posted Feb 14, 2018 12:40 PM ET


Thanks Martin

Answered by Anthony Swoope
Posted Feb 14, 2018 2:40 PM ET


Here is BSC article that discusses something similar. Might be useful to you, depending on your construction. https://buildingscience.com/documents/building-science-insights/bsi-101-...

Answered by Yupster
Posted Feb 15, 2018 9:10 AM ET


Thanks for the link. That's a useful article.

Answered by Martin Holladay
Posted Feb 15, 2018 9:20 AM ET

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