# Vapor Barrier Question:



## LEVELBEST (Dec 28, 2006)

Okay, most of you may have seen the mold thread about my moldy cabinet, etc. Well today they came out and cleaned up that issue, but also cut exploritory holes in a couple of exterior walls. Unfortunately, this is NOT a house I built, but one we moved into UNTIL we built our dream home, and I bought it after completion and didn't know a few things.

Anyways, after cutting the holes in the rock, we found that 1) there is poly over unfaced insulation 2) there is mold growing in all of the exterior walls, between the poly and the insulation 3) there is no tyvek on the house.

So here is the question. What has caused the issue? Isn't it code that a poly IS acceptable, while not what I would do, but isn't it acceptable by code if you DO NOT use a tyvek? If so, what is the reason for that?

Next question, what would each of you do if this was your home? I am tempted to wrap the house, put the vinyl back, then to tear out the rock, poly and insulation, and then put it back using a faced batt insulation.

What say you all? Any suggestions would be very greatly appreciated. This mold thing went from minor inconvenience to full blown nightmare in just one morning.

Thanks!
-Lee


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## SLSTech (Sep 13, 2008)

Unless I miss my guess, I think you are in the same climate zone that I am & you should not have poly on those walls All that moisture from the outside is migrating in & condensing on the poly. 

I would go from the outside, remove the sheathing, eliminate the mold on the studs & poly, remove the poly, resheathe, 1" or 2" thick foam board (taping the seams), then side it --- you can add FG back in the bays if you want, but I rather see cellulose or them left open with thicker foam board


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## jkfox624 (Jun 20, 2009)

Vapor barrier always goes to what is considered the warm side. In the south its out the north its in. I agree with SLSTech it seems it was done backward for your area. Is this in every stud bay throughout the entire house? If theres no housewrap, WRB whatever on the outside im gonna assume the windows and doors arent flashed at all?

I def agree that warm humid air is traveling through the wall hitting the vapor barrier and condensating but i would through out a good bet theres also exterior leaks in the house. Did any of the vinyl siding have mold growth on the face? Thats usually a good indicator of water penetrating somewhere and getting behind the siding. 

Heres some good articles on mold that may help you

http://www.buildingscience.com/resources/more-topics/mold


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## SLSTech (Sep 13, 2008)

Jeff, just as an FYI - while the mold on the vinyl siding might be a good indicator up north --- down here in the south, there almost always is mold or mildew on the exterior of the vinyl from the constant humidity.


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## jkfox624 (Jun 20, 2009)

SLSTech said:


> Jeff, just as an FYI - while the mold on the vinyl siding might be a good indicator up north --- down here in the south, there almost always is mold or mildew on the exterior of the vinyl from the constant humidity.


Ahh ok never really thought of that. Around here i can pretty much tell which windows are leaking. It leaves a very distinct mold/mildew triangle. Hot spots are always the bottom corners of windows, or where a roof ties into the side if a house and no one installed a kickout on the roof and they just ran j channel up the fascia.


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## LEVELBEST (Dec 28, 2006)

SLSTech said:


> Unless I miss my guess, I think you are in the same climate zone that I am & you should not have poly on those walls All that moisture from the outside is migrating in & condensing on the poly.
> 
> I would go from the outside, remove the sheathing, eliminate the mold on the studs & poly, remove the poly, resheathe, 1" or 2" thick foam board (taping the seams), then side it --- you can add FG back in the bays if you want, but I rather see cellulose or them left open with thicker foam board


Hammer, meet nail. You are exactly on top of the issue. I started to wonder if maybe this issue wasn't something that occurred during construction from rainy days or something, due to the fact that I couldn't SEE any moisture on the poly.....HOWEVER....I went into the dining room to a wall that my wife said she can actually smell mold coming from and cut another hole just a few minutes ago and there is moisture ALL OVER the poly, between it and the insulation.

I damn sure like the idea of doing all of the work from the outside. I hadn't considered it because I was trying to think of a way to insulate the walls again without being able to attach the insulation facing to the inside of the studs. You suggestion would definitely work. 

If you don't mind me asking you one or two more questions, could you pm me your email addy? 

Thanks to both of you who have offered suggestions to me, I really appreciate it! 

Lee


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## SLSTech (Sep 13, 2008)

PM was sent, but I will be glad to answer most questions here


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## LEVELBEST (Dec 28, 2006)

Here are two pics of just one of the holes we cut and found the mold growing on the insulation. You can see, obviously, the freaking clear poly that is covering the studs and insulation, just under the drywall. You will also note that this area is still wet, and it is wet with what definitely looks like condensation and not leaked water. On top of that, this past week has been the least humid week here in Upstate SC that we have had in WEEKS, and we haven't had one drop of rain in over a week, either. The other areas(four different ext walls) all appeared to be dry, but each one had mold growing in the same manner.


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## SLSTech (Sep 13, 2008)

The catch with water & heat - wet moves to dry & heat moves to cold 

Once you get water in the cavity, it needs to escape - unfortunately in your case it is being trapped by plastic (hot to cold) & also held in by the FG 

So I am wondering who saw that on TV & thought that applied everywhere - oops...

To bad they didn't spend their time on the exterior air sealing, WRB, etc...


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## nailit69 (Sep 8, 2010)

I don't know anything about the weather/climate in the south but here in the great northwest it rains all the damn time, while humidity might not be a problem here like it is there, moisture is.

I can't tell you how many newer homes i've gone into and seen mold. They want these things sealed up so tight they can't breathe... all in the name of energy efficiency.

Personally, I wouldn't/won't use a poly vapor barrier ANYWHERE in my houses, except on the ground in the crawl and under slabs. With all the rain here it can be weeks if not months before a house dries out completely after framing, and if you seal it in it can become a huge problem fast.

I Tyvek the house but I won't seal any seams or staple holes, Vycor around the windows, Quad caulking and Hardi Plank, Flashing above the doors and windows and i've never had a problem or callback. I've always said they need to breathe. You don't see many old drafty houses with mold problems, not saying it doesn't happen but you see where i'm going.

Another thing I don't understand around here is a home w/little or no overhang and flat roofs. Are you kidding me? we live underwater here why would you want to save water on your roof or let it beat the hell out of the side of your house?


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## ApgarNJ (Apr 16, 2006)

That is why I never use poly on the inside of the wall behind drywall. it's always asking for trouble. walls need to breath. i've never had an issues with tyvek on the exterior and either kraft batts or spray foam in the cavities. no mold, no moisture issues. Poly doesn't allow any breathing to happen in a house.


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