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cubsgrace
LSU Fan
New Orleans
Member since Sep 2007
1974 posts

Cathedral Ceiling Insulation Advice?
Planning to put R38-C in my cathedral ceiling next week.

I keep reading that the Kraft paper should ALWAYS face down (against the sheetrock) on a Cathedral ceiling but some people on various websites have said that in the South it is the opposite - they say in the South the Kraft paper should face the air gap between the insultation and the roof deck because the warm air is what holds most of the moisture. It sounds logical but with reputable websites saying to ALWAYS face it down toward the room, it is making me unsure.

Who is correct?

Also, am I good to not use baffles (vent chutes) as long as I have at least an inch air gap? I have 2/12 rafters.


eng08
LSU Fan
Member since Jan 2013
3900 posts

re: Cathedral Ceiling Insulation Advice?
Looked at dense packed cellulose for the unvented application?

A few years back I almost bought a camp with a uninsulated cathedral ceiling and it was like 110 in there in August. After all my research I kept coming back to right packed cellulose.


wickowick
LSU Fan
Head of Island
Member since Dec 2006
40241 posts

re: Cathedral Ceiling Insulation Advice?
What size are the rafters over that area? My bedroom has 2x8 rafters and I spray foamed the cathedral ceiling and it stays pretty damn cool even in the middle of summer.


shell01
Texas A&M Fan
Marianna, FL
Member since Jul 2014
325 posts

re: Cathedral Ceiling Insulation Advice?
Just renovated our house this year, including a cathedral ceiling, and never heard of putting the Kraft paper to the outside. My understanding is that kraft paper is flammable and needs to be placed against gypsum board.

Re: baffles, if you have a vented cathedral ceiling (which, from your mention of an airspace you do), you have to maintain that airspace from soffit to ridge. That typically requires a baffle at the soffit.

We used a foil radiant barrier from soffit/top plate to ridge, with spacers to maintain the airgap required for ventilation. Followed by r38 cathedral batts in our 2x12 rafters.


Nolaughingmatter
LSU Fan
Nola
Member since Aug 2018
473 posts

re: Cathedral Ceiling Insulation Advice?
2 x 12 rafters. I considered spray foam but it's expensive and I'm worried about consequences if water gets in below the roof deck, so I want it to vent to allow the flow of air to keep it dry.


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Nolaughingmatter
LSU Fan
Nola
Member since Aug 2018
473 posts

re: Cathedral Ceiling Insulation Advice?
I'll look into dense packed cellulose. So far I've been leaning towards vented, though.


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Nolaughingmatter
LSU Fan
Nola
Member since Aug 2018
473 posts

re: Cathedral Ceiling Insulation Advice?
I've never heard about the flammability of Kraft paper being a concern. I'll look into it, though. Paper has to be 451 degrees F to burn, right?


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ItNeverRains
LSU Fan
Franklin, TN
Member since Oct 2007
14679 posts

re: Cathedral Ceiling Insulation Advice?
My bedroom ceiling was originally 24' cathedral we lowered to 18', so there is a 6' gap in attic, but we did spray in walls and cellulose in ceiling in that room. I've never heard of facing paper the opposite way.

I will say my bedroom is the coldest room in our house during the summer, we have 10' everywhere else down except living room is 11'.


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Art Vandelay
LSU Fan
LOUISIANA
Member since Sep 2005
8255 posts

re: Cathedral Ceiling Insulation Advice?
I have seen this done so many ways and I really dont know what’s “the right way”. I would not use paper. Look into roxul. You’ll get a better product.

Is your soffit vented? I think I would want to eliminate any moisture being introduced to that space. I would not put baffles and if your soffit is vented I would seal it.

What is going to be your finished ceiling?


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fishfighter
LSU Fan
Baton Rouge
Member since Apr 2008
34005 posts

re: Cathedral Ceiling Insulation Advice?
quote:

Just renovated our house this year, including a cathedral ceiling, and never heard of putting the Kraft paper to the outside. My understanding is that kraft paper is flammable and needs to be placed against gypsum board.


This for sure.

quote:

Re: baffles, if you have a vented cathedral ceiling (which, from your mention of an airspace you do), you have to maintain that airspace from soffit to ridge. That typically requires a baffle at the soffit.


This also for sure.

I have R-38 in my cathedral ceiling and foam baffles above the insulation.


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notsince98
Missouri Fan
KC, MO
Member since Oct 2012
10750 posts

re: Cathedral Ceiling Insulation Advice?
Have you looked into using baffles and doing a dense packed blown insulation instead of batts? You'll get much better results with blown.


TDsngumbo
USA Fan
Member since Oct 2011
18040 posts

re: Cathedral Ceiling Insulation Advice?
quote:

Who is correct?


If you're married, it's your wife. If not, it's your girlfriend. If you're gay, it's both of you. If you're single and straight, it's your mom. If she's dead, it's your sister.


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Nolaughingmatter
LSU Fan
Nola
Member since Aug 2018
473 posts

re: Cathedral Ceiling Insulation Advice?
I recently installed vented soffits. The people that I bought the house from had painted over the soffits and sealed almost all the holes in the soffit. They also had gone into the attic and stuffed fiberglass insulation into the areas where the cathedral ceiling is supposed to vent into the Attic. I've been having a mood issue plus that room is always super hot. Since I removed the insulation blocking the flow from the ceiling into the attic and put in the soffit vents I no longer have the mold issue. When I cut out a section of sheetrock that had water damage I could see that the insulation is very old dirty flattened fiberglass insulation so I want to remove all the sheetrock from the ceiling, change out all of the insulation, and then put up new sheetrock.


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eng08
LSU Fan
Member since Jan 2013
3900 posts

re: Cathedral Ceiling Insulation Advice?
If you want vented another option would be to use 1x1 along the sides of the rafters, the install foil foam boards, then Sheetrock


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Nolaughingmatter
LSU Fan
Nola
Member since Aug 2018
473 posts

re: Cathedral Ceiling Insulation Advice?
I have not yet looked into dense packed blown insulation so I'll read up on it.


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