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-   -   Insulating and venting a cathedral ceiling (http://www.diychatroom.com/f19/insulating-venting-cathedral-ceiling-134488/)

fride360 02-21-2012 11:38 AM

Insulating and venting a cathedral ceiling
 
Here's my situation:

I need new shingles installed. My house has a cathedral ceiling throughout. It has 2x6 rafters and there is a 3' flat area at the top. I have noticed a little bit of moisture at the base of the ceiling in spots and I know it's due to insufficient venting. My question is since I need to replace the shingles is there a way to fix my problem by removing the decking and tackeling it from above? Or is there an easier way to do it?

Thanks a lot

jaydevries 02-21-2012 12:00 PM

yes but with only a 5 1/2 inch space i would look at doing a ventless roof by hiring a insulater to come in and fill cavity full of closed cell foam with a r value around 7 per an inch that will get you a r value around 38

here is a article on it

http://www.jlconline.com/cgi-bin/jlc.../View/0703insu

md2lgyk 02-21-2012 06:25 PM

Just be aware that solution is seriously expensive.

Gary in WA 02-22-2012 01:15 AM

Where are you located for your insulation value required?

Gary

jklingel 02-22-2012 09:13 AM

greenbuildingadvisor.com
 
I'd suggest you go to greenbuildingadvisor.com and search for cathedral ceilings. One of their blogs is specifically on insulating them. They frequently have questions about how to insulate, etc. Exterior foam may be your answer.

House Engineer 02-23-2012 07:50 PM

You could install a continuous roof ridge vent and continuous roof soffit vents, and leave a 2 inch air space between the underside of the roof sheathing and the top of the ceiling insulation. You don't have a lot of space to develop a large "R" value with your set up. You could maximize your "R" value,while minimizing the height of the insulation by using a type of insulation with a higher "R" value per inch, such as urethane.

The venting of each rafter space in a cathedral ceilings is required by the International Residential code (IRC).

jaydevries 02-23-2012 08:10 PM

here is the irc code requirments for unvented attics and enclosed rafters

some one might want to update their code knowledge

http://publicecodes.citation.com/ico...006_par004.htm

House Engineer 02-23-2012 08:22 PM

Not all cities in the United States have adopted the 2012 version of the IRC code that you cite.

I have never seen a problem with someone over-ventilating their rafter spaces.

I don't mean to argue, just trying to help.


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