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Old 08-20-2009, 06:50 PM   #1
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insulating vaulted ceiling


I want to reinsulate a "vaulted" ceiling, now they have two layers faced r-13 "pink to pink", can't be good with a double vapor barrier right?

I have 10" depth to work with, I think I could fit some r-40, do I used unfaced bats with the hangers? There is no attic void, just roof sheathing then the joists, then drywall ceiling (currently removed)...

there are vent baffles installed, those stay too? They just left 6" of insulation out at the ridge for flow, is this the right thing to do? Or should the baffles go right upto the ridge vent and insulate over them 100%?

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Old 08-20-2009, 08:34 PM   #2
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insulating vaulted ceiling


With 10" = do you mean you have 2x12's -1" for the rafter vents?
In that case you can use R38C - not normal R38
C stands for use on Cathedral ceiling

If you have 2x10's then you need R30C

I use kfraft faced

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Old 08-26-2009, 12:07 AM   #3
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insulating vaulted ceiling


There's the original rafters, then they sistered on another set 10 years ago when they remodeled. I measured roughly 10" but I will figure that out later when it comes time.

What is the difference between R38 and R38C for cathedral ceilings?

When do you use faced/unfaced? What about the plastic face vs. kraft paper?
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Old 08-26-2009, 01:23 PM   #4
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insulating vaulted ceiling


Rafter vents stay
I'm not sure if you are measuring after the rafter vents or total rafter depth
R38 is made to go in attics/other areas where it can fully expand to 12"
R38c is made to go in vaulted/cathedral ceiling where there will be a rafter vent. It has the same R value but is more tightly packed (10.25" I think) to allow room for the rafter vent

Only 1 vapor barrier/retarder
I only use the Kraft faced as a vapor retarder

You use unfaced when you are adding insulation on top of insulation that already has a vapor barrier/retarder

You use faced when a vapor barrier/retarder is needed/not already present

I have the R25 plastic "cased" insulation installed - it has many holes in the plastic
It is called Miraflex & is no longer made by Corning
http://saveenergy.owenscorning.com/2...insulatio.html
The plastic in this case is not considered a vapor barrier/retarder

Last edited by Scuba_Dave; 08-26-2009 at 03:34 PM. Reason: sp
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Old 08-26-2009, 03:29 PM   #5
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insulating vaulted ceiling


http://saveenergy.owenscorning.com/b...IncludeBlogs=2

Do I staple the flanges on faced fiber glass insulation to the face of the stud or to the inside of the stud?
When stapling is necessary in cathedral ceiling projects, always staple insulation to the face of the rafter to maintain the necessary 1" ventilation space. If Raft-R-Mate baffles have been installed up the entire length of the cavity, then either way is acceptable. In other projects, such as walls, either way is also appropriate.
Be safe, G
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Old 08-26-2009, 09:28 PM   #6
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insulating vaulted ceiling


Thanks that really clears up some grey areas.

There's roughly 10" plus the baffles (2x12 it seems). I was planning to tear out the baffles anyway and replace them, but what was said above indicates they're not needed so long as there's a natural 1" of breathing room? That will save me a lot of money, those baffles aren't cheap and I'd need 350 linear feet of 'em.

So with 2x12 joists, I can remove the old insulation/baffles and install R38C without any baffles in place? Where is that sold, Home Depot? Carter Lumber?
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Old 08-26-2009, 09:36 PM   #7
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insulating vaulted ceiling


I use R38C & still use the baffles on a 12" rafter
---rather then worry about insulation blocking the air flow at all

Most insulation places will carry the R38C
Home Depot /other big box stores its hit or miss
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Old 08-26-2009, 11:55 PM   #8
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insulating vaulted ceiling


Yes, according to the Pink Panther...... you will still have your 1" air space because the insulation is made that thick. It does not grow bigger than they make it for, baffles are extra money.
Here are quite a few questions and answers, enter your location question in the search box at the top: http://saveenergy.owenscorning.com/f...rgy_questions/

I found this, check your local: http://www.lowes.com/lowes/lkn?actio...K91&lpage=none

Be safe, G

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