Replies

1. Expert Member
   Dana Dorsett | Feb 23, 2018 02:39pm | #1

   Where are you located? (US climate zone, that is.)

   New construction, or retrofit?

2. GBA Editor
   Martin Holladay | Feb 23, 2018 02:43pm | #2

   Anthony,
   Q. "Would closed or open cell spray foam provide some level of water resistance during a minor flood?"

   A. Neither product will prevent water from entering your house. Neither product will prevent your drywall or studs from absorbing moisture. That said, open-cell spray foam will absorb and hold more water than closed-cell spray foam.

   Q. "Would the sheathing and studs be able to dry?"

   A. The answer to that question depends on how long the flood waters stayed at a high level before receding.

   Q. "Would rock wool be a better choice for insulation?"

   A. What are your criteria for making this choice? I think that mineral wool batts could be removed easier after a flood, and would allow the stud cavities to dry quicker than if the stud cavities were filled with spray foam.

3. 
   Remodelpro | Feb 23, 2018 02:52pm | #3

   Thanks Martin and Hello Dana,

   We are located in US climate zone 2A.
   This is a retrofit.

4. 
   JC72 | Feb 23, 2018 03:29pm | #4

   https://buildingscience.com/documents/building-science-insights/bsi-101-rebuilding-houston

   You want to use closed-cell SPF w/acrylic latex paint..

5. Expert Member
   Dana Dorsett | Feb 23, 2018 04:04pm | #5

   Are you stripping & replacing the siding?

   If yes, a variation on John Clark's referenced BSC article could work, getting of the structural sheathing and installing structural 2lb foam in the wall cavities instead. (It's expensive, but it works.)

6. 
   Remodelpro | Feb 26, 2018 01:37pm | #6

   Thanks Dana,

   We were not planning to remove the siding. The flood duration was short, the water was relatively clean and the plywood siding dried and is structurally sound. We die considerelliminating the cavity insulation and installing EPS insulation on the exterior under the hardiplank siding with a rainscreen but the client does not want to spend that much money rebuilding the structure.

7. 
   severaltypesofnerd | Feb 27, 2018 02:34am | #7

   What's the integrity of the old siding and wrb?
   Any moisture holding insulation becomes a disaster, if water seeps in due to wind driven rain or defects.

8. 
   Remodelpro | Feb 28, 2018 08:21am | #8

   Hi Bryce,

   The existing Hardiplank siding and #15LB building paper WRB are both in good condition.