Insulation goof

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  #1  
Old 12-14-02, 07:31 AM
bksrj60
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Insulation goof

10 years ago, I redid a room upstairs. I used Kraft faced to the heated side, then put 6 ml plastic over that and then the drywall.
I have not had any mold in the room.
Do I have mold in the walls with this double vapor barrier? At the time, I asked a builder if this was Ok and he said it was but I now I think I go a problem. Do I have a mess inside the walls. I live in Massachusetts.
 
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Old 12-14-02, 09:17 AM
T
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Vapor barriers

Vapor barriers keep warm, humid air from entering the wall cavity where it can condense on cold walls and create moisture problems. With two vapor barriers, sounds like you weren't taking in chances. Why do you think you now have a problem?

Do a search on this forum for vapor barriers. Click the little blue search button in the topic right corner.
 
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Old 12-17-02, 06:18 AM
bksrj60
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I looked over the replies in the forum. 2 said I would have no problem as you did and 1 reply said I could have a problem.
I then went to the web and did not find an answer to my question.
In one of the forums, I found a website
www.umass.edu/bmatwt/weather_barriers.html.

I emailed Paul Fissette, Director and Associate Professor of Building Materials and Wood Technology at UMASS, about my question and he replied the following:

You are ok. A vapor barrier is a material that has a "perm" (for permeance of 1 grain of water able to pass through a material per hour per square foot per inch of mercury). We do want to use a material with a perm less than 1 close to our warm side as you have done. A problem can arise when a double vapor barrier is installed in such a way that one VB is installed on the warm side of the wall and a second VB is installed on the cold side. This type of installation can trap condensation and moisture between the 2 VBs
and this is not good. The kraft paper is asphalt saturated and qualifies as a weak VB ~1. The poly is a strong VB ~0.06. They are both installed on the warm side and the temperature will be warm enough to keep the area above the dew point and you should no problem at all. The drywall and paper on the drywall are not VBs. Drywall has a perm rating of about 50.

His answer was the same as yours, twelvepole. Thank you for your reply.
 
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Old 12-17-02, 03:09 PM
T
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Vapor Barriers

Ah, a sigh of relief. Isn't research fun? Aren't you delighted your DIY project turned out so well? Your research results from UMASS provide an excellent technical explanation.

In regard to vapor barriers, it's easy to remember that we don't want warm, moist air moving to a cooler surface where it can condense and cause problems. Thus, if you lived in a warm climate, guess where you would put the vapor barrier?
 
  #5  
Old 12-19-02, 06:21 PM
rbisys
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Greetings,

Vapor barriers DO NOT prevent condensation from forming in the walls. If the dew point in the fiber insulation cannot pull moisture from the interior, it will get it from the out side air.

The only way you can tell if you have mold in the walls is to cut a section about 12"sq and break the VB and smell. If you do not have mold, it will be a miracle. Mold usally forms on the FG on the surface next to the sheathing. It can migrate from there to the drywall. The plastic will help prevent it intruding into the house. NOTE I said help, not prevent. Mold can be very intrusive.

Thank you for considering my opinion.
 
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