# Do I really need r50 insulation in garage attic?



## recklessrick (Oct 13, 2005)

Hi!

TD;DR: Would r20 or 30 be ok for my garage attic to help avoid condensation (and mold/mildew growth) on my ceiling drywall?

I have a house that's almost 2 years old. 
The attached garage has the master bedroom above about 2/3 of the garage. The rest is garage attic that is uninsulated. All walls are drywalled, insulated, VP of course while the ceiling is drywalled and VP with no insulation in the attic. I have a mild/mildew on some ceiling drywall on the uninsulated part. I understand this is because it gets humid in there as the snow melts off the cars (central Saskatchewan) and the warm/moist air goes up and meets the cold drywall of the ceiling and cools which then condenses on the drywall and mild/mildew grows. 

I'm going to blow in insulation and all the attic information I read says to use r50 (18.5 inches) but this isn't the house portion, just the garage. I'm thinking half of that perhaps? Just enough to keep the drywall from getting really cold in the winter.


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## recklessrick (Oct 13, 2005)

One more thing, couldn't I just use batts of insulation? It's not a big area, only about 275 sq feet.


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## Windows on Wash (Aug 30, 2011)

Is the roof vented?

Batts are fine.


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## recklessrick (Oct 13, 2005)

Windows on Wash said:


> Is the roof vented?
> 
> Batts are fine.


Yes, the space is well vented through vents in the roof and soffits all around. I was just up there this morning checking things out. Batts would be easier because it's a smaller space and access to everywhere I need is not an issue.


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## Windows on Wash (Aug 30, 2011)

Cover the batt if you can with some housewrap to prevent wind washing and R-Value degrading. 

Seal up the plates or around lights to keep the big moisture from getting up there.


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## recklessrick (Oct 13, 2005)

Windows on Wash said:


> Cover the batt if you can with some housewrap to prevent wind washing and R-Value degrading.
> 
> Seal up the plates or around lights to keep the big moisture from getting up there.


Right on, easy enough to do.


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## daveb1 (Jan 15, 2010)

rick were you concerned with moisture in the garage space? Everything mentioned so far needs to be done, but this will only prevent moisture in the attic space not the garage space.


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## recklessrick (Oct 13, 2005)

daveb1 said:


> rick were you concerned with moisture in the garage space? Everything mentioned so far needs to be done, but this will only prevent moisture in the attic space not the garage space.


Oh yes, I plan on watching the moisture in the garage as well. I will be moving the water out as it melts from now on. Taking some more precautions to keep moisture out. Worst case, I'll need to put and exhaust and intake fan system.


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## daveb1 (Jan 15, 2010)

Sounds like you've got it under control. Good luck. And Go Riders!!!!:thumbsup:


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## Windows on Wash (Aug 30, 2011)

daveb1 said:


> rick were you concerned with moisture in the garage space? Everything mentioned so far needs to be done, but this will only prevent moisture in the attic space not the garage space.


True but it will also keep it on the warm side of the assembly. If the moisture gets into the attic and reaches cold surfaces, more likely to have condensation but I completely agree with you.


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## recklessrick (Oct 13, 2005)

daveb1 said:


> Sounds like you've got it under control. Good luck. And Go Riders!!!!:thumbsup:


:thumbup:


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## Gary in WA (Mar 11, 2009)

You are basically; bringing inside an outside water/moisture source, Photo 7; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/ Cover with fire-code drywall on sleepers, keep it air-tight; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Gary


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