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Old 01-16-2012, 06:48 PM   #16
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Insulation Dilema- Vaulted/Cath. Ceiling


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Originally Posted by GBR in WA View Post
Where are you located in S.Cal.? There are 3 zones there; http://publicecodes.citation.com/ico...001_par001.htm

No foil-faced foam board on the rafter bottoms in your location, especially if you run AC, the rafters will rot without ventilation.

Gary
+1

Venting was specified by both Greg and me in this case. Your details need to be spot on in this case and if you change the dynamics of that space, you need to make sure you are not creating and issue for certain.

The reality is that the skip sheathing in that roof probably moves a bunch of air from the bottom to the top which is probably why you haven't had any issues previously.

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Old 01-16-2012, 07:58 PM   #17
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I dont think I have left out any details to be not spot on...... I appreciate all the feedback, I'm just trying to figure the best solution for this.

I have been researching this all day today and still not sure where I stand.
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Old 01-17-2012, 11:27 PM   #18
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I saw information to foamboard the bottom side of the rafters, or understood it that way, at least.
With a vented roof, which you sort of have, as WW said- the skip sheathing boards allow air movement- especially sideways, I wouldn't want foamboard on the bottom side because it is a Class 2 vapor retarder. You have a vapor retarder on the top side already- the builders felt/paper under the shakes. Running your AC would pull some hot moist air in through the roof to equalize the pressure difference of the room, that couldn't be made up elsewhere, depends on how well-vented the roof really is. (It may be fine, I don't know without a blower-door/smoke test).

If it was an unvented assembly, the foamboard would install tight to the roof sheathing to be an air barrier, leaving room for shake. Then add permeable insulation (if even needed in your location). http://resourcecenter.pnl.gov/cocoon...r/article/1520

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Old 01-18-2012, 12:40 PM   #19
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I'm guessing that our roof isn't vented well... by todays standards anyway. It is a 1950's california ranch style home, approximately 2000Sq.ft. and has no soffit vents what so ever, Only 4 gable vents
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Old 01-18-2012, 01:50 PM   #20
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Quote:
Originally Posted by GBR in WA View Post
I saw information to foamboard the bottom side of the rafters, or understood it that way, at least.
With a vented roof, which you sort of have, as WW said- the skip sheathing boards allow air movement- especially sideways, I wouldn't want foamboard on the bottom side because it is a Class 2 vapor retarder. You have a vapor retarder on the top side already- the builders felt/paper under the shakes. Running your AC would pull some hot moist air in through the roof to equalize the pressure difference of the room, that couldn't be made up elsewhere, depends on how well-vented the roof really is. (It may be fine, I don't know without a blower-door/smoke test).

If it was an unvented assembly, the foamboard would install tight to the roof sheathing to be an air barrier, leaving room for shake. Then add permeable insulation (if even needed in your location). http://resourcecenter.pnl.gov/cocoon...r/article/1520

Gary
I am also thinking that because of the skip sheathing It might be providing "Some" air flow and with it being in Southern Ca. and our pretty stable weather ( No snow ) that it could be why we haven't had a major issue.

Any advice on whether I should wait until we get our roof done and then deal with making this right?
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Old 01-18-2012, 06:24 PM   #21
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I'd wait on the insulation (as I look out the window at 7" of snow) and work on the electrical. That j-box is supposed to be exposed, accessible from the room, an outlet box, etc..... some sharp "sparkys" in our electrical section.

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Old 01-18-2012, 06:31 PM   #22
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Originally Posted by GBR in WA View Post
I'd wait on the insulation (as I look out the window at 7" of snow) and work on the electrical. That j-box is supposed to be exposed, accessible from the room, an outlet box, etc..... some sharp "sparkies" in our electrical section.

Gary

lol..... Yea, I was thrilled when I pulled the drywall and found all that goodstuff!

Just glad I found it now before it was too late and something bad happened. Still blows my mind that people will do such horrible work.

The electrical is no problem to fix and get right, it's all this insulating nonsense that has me all worked up. LOL.
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Old 01-18-2012, 06:36 PM   #23
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Least you have time before the snow comes......LOL.

Gary
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Old 01-26-2012, 11:36 AM   #24
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So I have had two roof estimates so far, and both contractors suggested foam board with ply on the exterior directly over the T&G. Non ventilated. I have one more estimate coming tomorrow so we will see what process they recommend. So If I go solid foam on the exterior, I just need to figure out what to do inside to insulate it properly in the dining room where drywall will be installed.
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Old 02-15-2012, 12:09 PM   #25
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So I have been busy with work and a gathering estimates and info in the last few weeks, but I think I have a plan now with all the info that I have collected.

At this point, We are planning on doing the following:
Install rigid ( have not decided on which kind or thickness) insulation on the outside when we do our roof, and R-13 batt's in the rafter bays and finished with drywall on the inside. Non vented.

Sound like I am on the right track?

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