Moisture On Insulation

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Old 12-07-06, 01:56 PM
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Moisture On Insulation

Hello,

I guess it is that time of year again. I had some venting issues last year in my main attic. I had a new roof with plenty of soffit vents and a ridge vent isntalled. I also put a product by Owens Corinng called Attic Blanket R25 over my exisiting insulation. I checked the attic today and noticed in the pink poly covering (top Cover)of the Attic blanket that there was some moisture that had built up. It is not in one specific area it seems to be in most of the attic blanket. I also have some slight condensation on the roof sheeting a bit of water drips on the nail heads. It is not alot of condensation but I know this is not how it is supposed to be and I have alot of $ invested in the renovation of this home. It was built in 1968 and the exisiting insulation I think is R19 and is origianal. Help? How in the world could my attic not be venting properly? It seems to be the same tempature as outside. My exhaust fans seem to be vented ok. There may be a few gaps but I just dont see how that could produce condensation with the amount of venting I have.

Thank You for your assistance,
 
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Old 12-07-06, 03:02 PM
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Make sure all fans vent to the outside. Or you sure moisture is not comming from living area? Do you know the RH% of the living area!
 
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Old 12-07-06, 08:13 PM
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your most alarming words were: "pink poly covering (top cover) of the attic blanket". Its not hard to diagnose that problem!

When using insulation on top of existing insulation, you should NOT have additional vapor barrier or kraft facing on the insulation, and it especially should not be facing UP when seen from the attic! If used in an attic, the vapor barrier would hopefully be on the bottom side of the bottom (original) layer of insulation next to your ceiling (warm side).
 
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Old 12-07-06, 08:36 PM
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Wink

Attic Blanket R25 over my exisiting insulation. I checked the attic today and noticed in the pink poly covering (top Cover)of the Attic blanket that there was some moisture that had built up.

Im with XSleeper On that insulation you put in. Anytime you add more insulation up there you dont use any with paper or poly on it . To go over the old insulation.
You didnt block the rafters so the air from the vents in the over hang cant get up into the attic and out the top vents in the roof????

My exhaust fans seem to be vented ok. There may be a few gaps but I just dont see how that could produce condensation with the amount of venting
It sure can

You need 1 sq ft of vent for every 150 sq ft of attic. 1/2 in and 1/2 out. For a attic vent fan . sq ft X 0.7=CFM of the fan.

ED
 
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Old 12-08-06, 12:25 PM
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Thank You all for the info. I just checked with OC and the pink poly is not a vapor barrier it is only contains the insulation. After doing some more investingating I think I might have the problem isolated. The original insulation from 1968 (Johns Manville) does not appear to have a vapor barrier on it. I think the warm moist air is forming condensation when it its the cold pink poly. I guess I will need to tear out the old and put down some with a vapor barrier. (Not Fun)!! Thanks Again,
 
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Old 12-08-06, 02:39 PM
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When you remove the old insulation, seal all gaps where warm, moist air from below could pass into attic. As indicated, vapor retarder faces down toward heated space below. Insulation goes on top. Note: Once insulation gets wet it tends to lose its insulative qualities. Too, amount of required ventilation needs to be calculated. When adding to existing insulation, unfaced fiberglass blanket is recommended. Owens-Corning's R-25 Attic Blanket(C) is recommended for such a situation. There are baffles available for keeping insulation from blocking soffit vents.
 
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Old 12-09-06, 08:02 AM
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Exclamation pink poly attic blanket

I believe tearing out your insulation is the wrong first step in solving this problem. also, from your description of moisture on the underside of the roof sheathing, I beleive you have moist warm air infiltration into the attic from someplace like an improperly installed/sealed bathroom exhaust fan, can lights. attic access panel or such. Which is then dripping down onto the insulation and poly wrap is preventing this insulation from being destroyed and useless. eliminate and seal these air infiltrations to your attic and the moisture should disapear If the poly wrapped attic blanket is an owens corning product you may want to contact them directly for technical advice on this problem. I believe they had this problem with this product several years ago and issued instalation guide lines to prevent this issue.
p.s. I worked in an attic pulling out 600 Sq feet of wet matted insulation over ten years ago and the only place we found for moisture infiltration was a bathroom exhaust vent pipe that had cracked open at the joint less than a quarter inch by 1 1/2 when someone evidently inadvertantly stepped on it at some time in the past. we replaced the insulation and fixed the pipe. I was up in that attic at thanksgiving this year and the insulation is dry as a bone. double checking all your venting pipes and and any openings into the attic space is imperative to solve this problem or you will be spending a lot of money on insulation!!!
 

Last edited by mtk16078; 12-09-06 at 09:03 AM. Reason: additional info
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