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Old 11-04-2011, 06:29 PM   #1
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Attic Insulation - vapor barrier???


Hi,

I'm sorry if I didn't find the answer posted in the forums but here is my question:

I have a ranch with 2-3 inch bats for insulation. Lots of holes and open spots. I'm planning on adding some insulation and I'm wondering what the best option is?

I don't have a vapor barrier - From what I understand unless the vapor barrier is "seamless" it is almost useless. Is there a reason to try and add poly between the rafters, or use faced bats?

Or am I better off pulling up the small amount of insulation I have, air sealing as much as possible, and blow insulation in?

We are in NE ohio.

Thanks for any suggestions,
Dan

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Old 11-04-2011, 08:56 PM   #2
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Attic Insulation - vapor barrier???


Vapor barrier is surface measured, you are confusing the two: http://www.greenbuildingadvisor.com/...cience-podcast

Faced batt will work, not to worry about full coverage of the paper facing: http://www.insulating-products.com/p...lation_FAQ.pdf

Air seal first, then cellulose: The "biggest loser" in fiberglass insulation....

Gary

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Old 11-04-2011, 10:13 PM   #3
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Attic Insulation - vapor barrier???


Thank you for the thoughtful reply - I appreciate suggestions backed by evidence.

If i understand correctly - provided I have well painted moisture repelling ceilings - any air leaks will contribute far more moisture contamination from air transport then the threat of moisture from diffusion.

Thanks again,
Dan
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Old 11-05-2011, 12:11 PM   #4
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Attic Insulation - vapor barrier???


"If i understand correctly - provided I have well painted moisture repelling ceilings - any air leaks will contribute far more moisture contamination from air transport then the threat of moisture from diffusion."------ exactly. Plus, with cellulose, a v.b. is not required: http://www.applegateinsulation.com/C...id=249418&fd=0

Air-sealing importance: http://www.jlconline.com/cgi-local/v...170a32100a05c7

The stack effect: http://www.wag-aic.org/1999/WAG_99_baker.pdf

Confusion about diffusion: http://www.buildingscience.com/docum...bout-diffusion

http://www.greenbuildingadvisor.com/...stop-air-leaks

This should clinch it for you, Dan, lol, 1/3 quart vs. 30 quarts: http://www.buildingscience.com/docum...apor-retarders

Gary
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Old 11-05-2011, 10:11 PM   #5
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Attic Insulation - vapor barrier???


Quote:
Originally Posted by junkman View Post
Thank you for the thoughtful reply - I appreciate suggestions backed by evidence.

If i understand correctly - provided I have well painted moisture repelling ceilings - any air leaks will contribute far more moisture contamination from air transport then the threat of moisture from diffusion.

Thanks again,
Dan
You got it.

Not many customers do but with all of GBRs reading, you got it nailed down.
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