Two Vapor Barriers?

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  #1  
Old 12-31-04, 12:31 PM
Burbank
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Two Vapor Barriers?

I am in the process of finishing a pole building. The building will be used as my workshop and it will be heated, I live in Washington State. The contractor that put up the exterior placed R-23 Kraft Faced fiberglass insulation between the 2 X 6 rafters with the facing against the metal corrugated roof. This means that the vapor barrier is facing the roof, not the inside of my building. I plan to install sheetrock on the ceiling. It is not uncommon for the temperature to dip below zero here, and in the summer reach 100 for a month or more. My question is can I place a 4 mil poly vapor barrier on the interior side of the roof thereby wrapping the fiberglass insulation in two vapor barriers
 
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  #2  
Old 12-31-04, 02:29 PM
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Join Date: Jul 2004
Location: Chester, IL
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You should first call your builder and ask him how he plans to correct the fact that some of the materials that you paid dearly for him to install, were not installed according to manufacturer instructions. Whether he changes it, or you do (not for free I might add), it should be turned around so the vapor barrier is to the hot side (inside). THEN you can put your 4mil on the wall, then drywall.

If you put 4mil on the way it is, your insulation won't last long, moisture will collect between the 2 VB's and waterlog your insulation, and then it will be YOUR expense to replace it (not even counting having to remove/replace drywall).
 
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Old 12-31-04, 04:56 PM
Burbank
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That was not the answer I was hoping for, but thank you for your quick response. Getting the contractor to correct this is not an option. The Kraft insulation is stapled on from the top before the sheet metal was installed. The only way to take it off is to rip it out, I know I have tried. I will have to rent a scissor lift as the peak is 21' high. How do you suggest I secure the insulation once I have reversed it. Do you think twine would work? It has to be held up there until I am able to install the vapor barrier. The building is 28' X 48'. What a mess.
 
  #4  
Old 12-31-04, 06:50 PM
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Join Date: Jul 2004
Location: Chester, IL
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If the roof isn't too steep, you could use hangers to keep the insulation in place (little stiff lengths of wire that have sharp points..ya jam in one side then give it a little bend so the other side will fit).

If it is too steep, you may just have to staple as best you can with what paper is left, and use the hangers. (that may not be a terrible idea even if you do have a shallow roof pitch) If you're careful while ripping it out, you should be ok. Even if you can get only a few places stapled, it's better than nothing. That along with the hangers should keep it up until you can drywall it.

I know that's not what you wanted to hear, but in 10 years you'd be: A) cold as h*** or B) ripping down drywall to replace insulation anyway. Imagine the moldy, nasty smell of 1500 sq. feet of wet insulation
 
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