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Old 05-09-2020, 01:00 PM   #1
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Insulating walls in hot humid no sheetrock


Hi all first post on this site! I’ve been slowly remodeling an old house in New Orleans and am a bit stumped on how to insulate the walls.

My wall assembly from outside in is:

1. Cypress siding
2. 1/4 plywood strapping (for small rainscreen)
3. 30# tar paper
4. Osb

Now I am considering two insulation options

1. Rockwool followed by vapor open Housewrap as interior air barrier

or

2. 3 inch Polyiso with the fiber facing cut and cobbled into the bays set on 1/2 rippers For an additional drying space between sheathing and the polyiso

Then reinstalling the original 1/2 heart pine wall covering.

I’ve seen people insulate then install drywall as air barrier with wood paneling on top of Sheetrock but I’ve been way too much moldy Sheetrock and soggy batts down here and am looking for a better way!

Any other builders in the south with similar w

Thanks and I appreciate any insight!

Frankie
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Old 05-09-2020, 01:42 PM   #2
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Re: Insulating walls in hot humid no sheetrock


What is the local code, they usually have it figured out.

If you will be running AC you want to stop the moist air coming in from the outside and stop cold air from getting to that surface.
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Old 05-09-2020, 01:57 PM   #3
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A ha! Yes good idea. I’ve reached out to the safety and permitting office here on multiple occasions and they seldom get back to me! I will try again though. Pretty standard practice to use Sheetrock here although home of the older homes have wood wall covering but usually no insulation. Originally I was thinking no ac but my tune has changed after a few hot summers.

I wonder if an air tight yet vapor open house wrap would do the trick stapled to the front of the studs. Maybe would help keep the cold ac inside air in the summer from migrating into the Rockwool insulated wall cavity?
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Old 05-09-2020, 01:58 PM   #4
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Ps! Thanks for the input definitely been a learning process!
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Old 05-09-2020, 02:05 PM   #5
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Re: Insulating walls in hot humid no sheetrock


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Ps! Thanks for the input definitely been a learning process!
You might talk to the pros that sell insulation and maybe any new house building going on?
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Old 05-09-2020, 02:10 PM   #6
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Yes good idea. I’ll contact both Roxul and maybe a few house wrap manufacturers as well. Thank you
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Old 05-09-2020, 02:17 PM   #7
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Re: Insulating walls in hot humid no sheetrock


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Yes good idea. Iíll contact both Roxul and maybe a few house wrap manufacturers as well. Thank you
What ever you do, you can buy trouble with poor fitting insulation. So that is the most important part, take your time and make sure it fits good.
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Old 05-09-2020, 02:21 PM   #8
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Re: Insulating walls in hot humid no sheetrock


Look at some Youtube videos by Matt Risinger, He is in a similar climate- Texas. He has several videos on insulation and air and vapor barriers.

I would use rock wool insulation with paperless drywall.
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Old 05-09-2020, 02:29 PM   #9
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Yes thanks for the input! And Yes Matt Risinger has some really good inisghts. I saw a video of his where he installed wood paneling over drywall. I guess my dilemma is I’d like to forgo the drywall as I’ve seen moldy drywall and it feels silly/wasteful to Sheetrock a whole house just to cover it with paneling. I wonder if a vapor open but airtight housewrap would be an acceptable alternative under wood paneling?
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Old 05-09-2020, 02:38 PM   #10
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Re: Insulating walls in hot humid no sheetrock


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Originally Posted by Askeena View Post
Yes thanks for the input! And Yes Matt Risinger has some really good inisghts. I saw a video of his where he installed wood paneling over drywall. I guess my dilemma is Iíd like to forgo the drywall as Iíve seen moldy drywall and it feels silly/wasteful to Sheetrock a whole house just to cover it with paneling. I wonder if a vapor open but airtight housewrap would be an acceptable alternative under wood paneling?
You have to consider what the cause was for the moldy dry wall you have seen. What ever that reason is would be the same for dry wall or wood and if you have air leaks thru vapour barrier dirt will build up on that and mold will grow. All of that is just a symptom of a problem. The problem is air flow and cold and warm meeting somewhere. And that somewhere is where you find mold.
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Old 05-09-2020, 02:44 PM   #11
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Yes good point. Plus here in New Orleans things get drenched/ flood. It’s no wonder that the old plaster walls/wood walls without insulation seem to outlast new walls with insulation and drywall. The downside is a mighty hot or mighty cold house!
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Old 05-10-2020, 02:12 PM   #12
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Re: Insulating walls in hot humid no sheetrock


https://www.lsuagcenter.com/NR/rdonl...oorsLOWRES.pdf


This says floors, so close to boards only walls, maybe. Sorry not familiar with your area or even reading this article. It may help you. I searched "vapor barriers in new orleans".



Read the article with a grain of salt. I was talking about this just a few days ago, although my area is nj. There is some concern that vapor barriers are being used indiscriminately, esp in very cold regions, ending up with trapped moisture. So if you refer to an article, check when it was written. Search for name LISTIBUREK and read what he says about vapor barriers. He says a lot of sensible things, even if it may be against the "industry" standard. But his examples deal with a drywall, that can be air sealed. Your boards-only will allow lots of air to leak.
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Old 05-10-2020, 02:55 PM   #13
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Re: Insulating walls in hot humid no sheetrock


In the north our walls dry out. In the south your walls dry in. Vapor retarder out in the humid Deep South.
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Old 05-10-2020, 03:40 PM   #14
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Re: Insulating walls in hot humid no sheetrock


carpdad, that LSU AG Center is a great resource.In fact I was able to email them to get some input. Thanks for sharing.

Old Thomas, yes I've heard that it's best practice here in the Deep South to have the vapor retarder on the outside. I guess I am trying to figure out how to add an "airtight" yet vapor open material to the inside of the wall assembly prior to putting up the wood paneling. I'd rather not install drywall and was thinking about intello plus or delta vent s with seams taped as my air barrier stapled to the face of the studs.

Looks like intello plus's vapor permeability changes from 2 perm to 13 perm depending on humidities. Delta vent s stays vapor open at like 60 perms i believe. Both tout being air barriers and was curious if done well this would be an acceptable alternative to drywall as my vapor open air barrier under the wood paneling?
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Old 05-11-2020, 07:37 AM   #15
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Re: Insulating walls in hot humid no sheetrock


https://bct.eco.umass.edu/publicatio...tion-barriers/


There is another article by sonya somebody who works for grace (ice shield company).


Both articles seem to assume vapor permeable materials do work and used correctly, will control vapor and condensation. Both articles assume there is no air leakage, that is, open joints are taped at least.


I was interested about air sealing and drying out so did some research and fast reading. I think it comes down to if you believe the claims.


I was thinking this could work: use 30lb felt (tar paper) and tape the seams. Paper can turn the corner and tape the overlaps. Maybe caulk the top and bottom plates for air seal. Then extra 1/4" thick slats over the studs then install your boards. Felt is vapor permeable, air barrier and the gap allows much more drying out. Just an idea. If you believe in your smart wrap, seems to me that your idea is good.


Also wanted to add but not sure if proven anywhere or body, felt absorbs water (above article) which would help not to condense. Also if not ac, outside and inside temps would be similar so no condensation. If ac, ac would dehumidify inside air and help with drying.

Last edited by carpdad; 05-11-2020 at 07:42 AM.
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