How To Install Roxul Insulation In A Crawl Space Ciling. - Insulation - DIY Chatroom Home Improvement Forum


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Old 12-10-2011, 11:02 AM   #1
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how to install roxul insulation in a crawl space ciling.


I have already encapsulated the crawl space with a 12 mill vapor barrier and also used spray foam in the wall cavities.
but the house wood floors is still feel cold.
We removed the old fiber glass insulation and have not installed anything else yet.
I'd like to put roxul R23, which is 5 1/2" thick.
I live in Maryland and I like to know if I need a vapor barrier in between the floor joists before installing roxul.
Is this a good way to go.

Thank you.

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Last edited by plastic; 12-10-2011 at 11:06 AM. Reason: miss spelling a word
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Old 12-12-2011, 04:17 PM   #2
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how to install roxul insulation in a crawl space ciling.


Quote:
Originally Posted by plastic View Post
I have already encapsulated the crawl space with a 12 mill vapor barrier and also used spray foam in the wall cavities.
but the house wood floors is still feel cold.
We removed the old fiber glass insulation and have not installed anything else yet.
I'd like to put roxul R23, which is 5 1/2" thick.
I live in Maryland and I like to know if I need a vapor barrier in between the floor joists before installing roxul.
Is this a good way to go.

Thank you.
I am doing a similar project also wanting to use Roxul and some very helpful folks have guided me. What kinda of crawl space is it? Do you know if it's vented (unconditioned) or unvented? I think you'll be ok without a vapor barrier as the plywood floor sitting on the joist acts a vapor retarder plus the roxul resists moisture. But that all depends on your setup!

Few other things to check since the floors still feel cold that I am in the process of doing in my home. Check the rim joists, mine were lightly stuffed with smashed up fiberglass. I can't tell you how much air they were letting in. I just sealed with a good sealant and cut to fit foam board (XPS) sealed in place with great stuff foam. Also seal the sill ledge, I had a quarter inch gap in some spots I checked where I can see outside. As you can imagine the air was just gushing in. Also seal up some holes for cable lines, electric, etc... if you have any running down there.

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Old 12-12-2011, 05:27 PM   #3
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how to install roxul insulation in a crawl space ciling.


If you don't have a high water table in that area, insulate the crawlspace wall and supply some conditioned air to the crawlspace via a supply side duct.
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Old 12-13-2011, 07:31 AM   #4
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how to install roxul insulation in a crawl space ciling.


Thank you for responding to my post.
My crawl space is as a mention 24'x31' and is around 3 1/2' in height.
I started by removing the old fiber glass insulation on the crawl space ceiling and then replace the 6 mill vapor barrier with a 12 mill from crwal space concept, it is great stuff. I would recomend this to anybody.
The crawl space used to be vented, not anymore, I seal all vents with foam board from the inside and put spray foam around the edge to seal it
completely.
Then I used foam it green spray foam insulation on the joists cavities, but I was only able to spray 1" thick because this stuff it is expensive.
My wife did not want me to put fiber glass insulation back in tha crawl space because she thinks that if I do, mice will come back.
Therefore I started doing research and came acrross Roxul insulation, and
I think that once I put this in the crawl space ceiling, the hose floor should feel a little bit warmer.
I will be using R23 roxul, which is about 5 1/2" thick, I call roxul in canada and they told me that I do not need a vapor barrier as long
as long as the crawl space has been encapsulated.
I hope that this helps someone.

Thank you for your input.
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Old 12-13-2011, 08:29 AM   #5
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how to install roxul insulation in a crawl space ciling.


Quote:
Originally Posted by plastic View Post
Thank you for responding to my post.
My crawl space is as a mention 24'x31' and is around 3 1/2' in height.
I started by removing the old fiber glass insulation on the crawl space ceiling and then replace the 6 mill vapor barrier with a 12 mill from crwal space concept, it is great stuff. I would recomend this to anybody.
The crawl space used to be vented, not anymore, I seal all vents with foam board from the inside and put spray foam around the edge to seal it
completely.
Then I used foam it green spray foam insulation on the joists cavities, but I was only able to spray 1" thick because this stuff it is expensive.
My wife did not want me to put fiber glass insulation back in tha crawl space because she thinks that if I do, mice will come back.
Therefore I started doing research and came acrross Roxul insulation, and
I think that once I put this in the crawl space ceiling, the hose floor should feel a little bit warmer.
I will be using R23 roxul, which is about 5 1/2" thick, I call roxul in canada and they told me that I do not need a vapor barrier as long
as long as the crawl space has been encapsulated.
I hope that this helps someone.

Thank you for your input.
Thanks Plastic for the information you got from Roxul, that helps me allot. I am doing pretty much the same exact project. I would like to use spray foam on the bottom of the floor but like you said it's costly. Plus I can do the job at my own pace little by little when funds are available. I was looking at the EXACT same 12 mil vapor barrier. I am glad you give it a good recommendation because I will be eventually purchasing that same exact vapor barrier along with the tapes and foundation pins. My wife is anti-fiberglass too, she feels it somehow gets into the ventilation and travels up to the house air. What's down there is just flat out nasty old fiberglass, I really dislike it too. While expensive I am excited to use the Roxul, the specs on it are amazing and I am eager to see how easy it cuts which makes the jobs allot easier for those hard nooks and cranny areas. Thanks again!
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Old 12-18-2011, 01:27 AM   #6
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how to install roxul insulation in a crawl space ciling.


Plastic, welcome to the forum!

Sounds like I'm a bit late here.... for others reading; As WW said above- http://publicecodes.citation.com/ico...008_par002.htm

http://www.buildingscience.com/docum...n-crawlspaces/

http://www.buildingscience.com/docum...ance-and-codes

Gary

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