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Insulating a non vented vaulted ceiling... Need Help

Insulating a non vented vaulted ceiling... Need Help

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  #1  
Old 01-16-12, 02:54 PM
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Insulating a non vented vaulted ceiling... Need Help

I am hoping to get some feedback on the issue I have found in my house while redoing our dining room. The electrical issues that can be seen in the photo's are one of the reasons I pulled the drywall to begin with and are being corrected. My dilemma at the moment is how to properly insulate this area of the house.

The roof/ceiling is 2x4 construction and pretty much "Non Vented" (to the outside of the house anyway). Whoever re drywalled this room at sometime before I owned the house installed FG insulation in some places and none in others. It was poorly done. The drywall is chalky and feels dried out. I am going to pull the rest down and redo it all but my dilemma lies in how to insulate this area the right way.

In this photo it shows the lower side of the room. The wall joins the dining room and our garage... Sooo obviously not vents here.

http://craftwerks.smugmug.com/Other/.../IMG1221-M.jpg

In this photo, It shows the higher side which shares the wall with out kitchen. There is no blocking and it is open to our attic space.

http://craftwerks.smugmug.com/Other/.../IMG1220-M.jpg

Here is an overall shot of the ceiling.

http://craftwerks.smugmug.com/Other/.../IMG1222-M.jpg

Here is the adjacent room that is also vaulted. This has been poorly insulated as well (from the inside and covered with bead board) and is going to get redone. This room has 4x6 beams, T&G for the ceiling.

http://craftwerks.smugmug.com/Other/.../IMG1223-M.jpg

My plans are to have it insulated from the outside when we redo our roof so that we can leave the beams and T&G exposed.

I am in Southern California FYI.


Any input would be much appreciated!

Thanks in advance!
 
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  #2  
Old 01-16-12, 03:25 PM
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I'm having trouble piecing the pictures together to see the whole house. If there are no exterior walls to try to create high and low vents, then roof vents or no vents should be considered. I assume you are in a predominately air conditioning area.

Natural venting with high and low vents does not work well without some elevation difference between the two vents. Where you say the one side is open to the rest of your attic space, is that area vented with ridge or gable vents? Wherever there are rain gutters or where there could be gutters, they make edge vents that can be installed under the first row of shingles. Up high they also make an under shingle vent for places where a roof meets a wall, thus no ridge.

When I can figure out the structure I may be able to suggest more.

Bud
 
  #3  
Old 01-16-12, 03:28 PM
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I don't see any t&g so I am not sure what you mean by that. If you plan to insulate from the outside and leave everything open, then why do you want to re-insulate and put the drywall back up?

Building Science Corporation has great information about this topic. Go there and read.

The primary reason to vent is to prevent condensation from forming on the roof deck. I'm not sure how much of a problem this is in the area where you live. It is a big problem in cold climates where warm moist air from the home meets the cold surface of the roof in the winter. I suppose this can happen in reverse in your home with air conditioning running. The two methods that are sure fire ways to stop this condensation from occurring are the one you already mentioned and closed cell spray foam on the inside.
 
  #4  
Old 01-16-12, 03:39 PM
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Thanks for the input.

The T&G is covered up in the photo by beadboard that was installed by the previous owner. It will be removed when we redo our roof and insulate that part of the roof in a proper manner.

The photo's of the room with the drywalled ceiling is going to get re-drywalled and does not have any T&G.

I am in the san fernando valley in Southern California and we see temp down to the 40-50's this time of year and 110+ during the summer.

There are no exterior walls to vent to and installing any sort of venting on the roof will be difficult with the roofing tiles that were used.
 
  #5  
Old 01-16-12, 04:30 PM
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Yeah. You need to go sealed. You also don't have room for venting and insulation in the bay. Filling the cavity with CCSF will do the trick. But if you plan to insulate on top of the roof when you redo it, I'm not sure there is a reason to do it now. You can also put foam sheathing opn the inside and then drywall over that.
 
  #6  
Old 01-16-12, 05:44 PM
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Thanks for the replies.....

If I spray in CCSF and then insulate on the outside when we do our roof... I'm not looking @ having any issues am i? I just figured it would be insulated that much more.
 
  #7  
Old 01-16-12, 06:41 PM
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I'm not sure if you would. Though I'm not sure it is worth the extra expense. The CCSF foam would give you at least an R21. I don't think you have much more to gain in the extra cost of the foam on the outside.
 
  #8  
Old 01-18-12, 10:36 AM
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I think I may need to have a roofer come out and look at insulating the T&G part of the roof and go from there. Because the two rooms share the same part of the roof, whatever I do in our dining room to insulate on the inside might not be ok with how the insulate from the outside when I get that done. At least that is what I got from some of what I have read.
Our house only has gable vents and no soffit vents which has not made my research any easier to find what I need.
 
  #9  
Old 01-21-12, 03:58 PM
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I had done a little research 2 years ago on adding depth to my roof cavity from the outside also because of only 2x4 rafters. However, I was looking at fiberglass. This was being done thru a state weatherization program and they wouldn't use spray foam. I know with the deck being left on, even with everything else peeled off, we couldn't leave the layer of deck between two layers of fiberglass, however, I suspect that with foams's sealing properties this may not apply. You might want to check with the supplier of your new roofing materials. That's where I actually found my info.

A thought since you are thinking about doing something that may be a little out of the ordinary, that all contractors are not created equal and that you might want to get input from as many as 3 or 4 experienced roofers. I'm sure you will be amazaed at the differences of opinions on the matter!
 
  #10  
Old 01-26-12, 09:09 AM
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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 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.
 
  #11  
Old 01-27-12, 09:54 AM
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J_Loc, Looks like you're doing some of the homework! I don't know if or how much $ plays into your decision-sounds like you just want a good insulating job. I hate to sound like I'm bashing contractors-sorry guys/gals-but a LOT of the time the "easy way" is the choice. I'm short on time right now, but I took a quick look for the R-value that is suggested for your area & couldn't immediately come up with it. Cold (Air cond.) settles, so loss thru the roof is minimal compared to those of us in MN who have heat escaping as our big concern. However, moisture would be hugh for you with the hot exterior sun and the cooler interior. If you're suggested R-value for the roof can be obtained with the ccsf that would fit in the 3 1/2" you have, I would be inclined to pull the ceiling and have it sprayed. If you need or want HIGHER than that R21 (I believe is 3+" of foam) then you may want to finish your ceiling & when you have your roof pulled, have them pull the deck also. Add a 2x4 parallel on top of your existing rafters to double your cavity depth and fill that with spray foam. It will be the tightest most moisture proof roof that you can probably get. Your contractors have said to put rigid foam on the deck and then ply on top, which is essentially a new deck anyway. You'd be paying the extra for the doubling depth of the 2x4 rafters and pulling up the deck. (You will also be paying for having the fascia redone which they would have to do anyway if they're putting on rigid + ply or OSB.) They will generally want to avoid pulling the deck-but as you said, that leaves YOU with dealing with the uninsulated ceiling inside (which isn't going to be free either). I would not leave that area open because it could be a high moisture collection area with no venting.(?) You might want to look into the rebates or tax credits related to both the insulation and new roofing. If you don't know about the roofing, there now are Energy Star shingles & the tax credit or rebates, maybe even both could be quite substantial. Be assertive with a contractor if you turn this over to one because they usually want to use products that they may actually have on hand, like to use, have cheap access to or whatever and may resist using what you might find to be a great product with long term savings for you in the end. Good luck!
 
  #12  
Old 02-15-12, 10:12 AM
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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?
 
  #13  
Old 02-16-12, 05:35 AM
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Sounds like you have sufficient info from several sources. Guess you should be fine. Is the rigid foam on the roof going to be taped at the seams? Just a thought. Do you know what thickness of ply or OSB is going over the rigid foam to nail the shingles to? I would go 7/16 or 1/2 for secure nailing. Obviously you don't need the structural integrity being as you're not pulling the original roof deck, however under the size of 7/16 might be awfully thin for nailing shingles to hold into in severe winds. As I believe I mentioned before, you might want to check with the shingle supplier for specific info as you may end up with no warranty if you don't follow their recommended installation. I'm not sure of the actual sealing properties of the rigid foam, even if it's taped, so you may need a (6) mil poly vapor barrier after you install your figerglass and prior to the sheet rock. Stopping the flow of air from inside to outside is the idea. Kraft faced fiberglass really is not that efficient to stop air flow. In the Midwest, only people that don't know better are still using the Kraft faced. I believe all pros use the unfaced fiberglass friction fit with poly. Sealing it at the outside edges with a continous bead of acoustic adhesive and at 16" overlap of the poly seams with house wrap tape is code now I believe. The acoustic adhesive stays soft and the poly sticks well to it. I don't believe that there is another product that the poly sticks well to indefinitely. One contractor told me to use just any latex caulk but the poly doesn't stick to it once it cures and clearly is not the product of choice. Hope it all goes well.
 

Last edited by shecandoit; 02-16-12 at 06:01 AM.
  #14  
Old 02-20-12, 06:58 AM
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Here is what I did to throw another idea into the mix.

We have an old 1910s-1920's 1.5 story bungalow with some slanted ceilings on the second floor. Most of these ceilings had no insulation in them and connected to a small attic space above.

When I redid the roof I filled the rafter bays with 3.5" (only 2x4 rafters) polyiso board cut short and foamed in place. I then covered all the rafters with 1" foil-faced polyiso board with taped seams that I caulked and nailed down as a thermal break. I then installed 2x4 sleepers on their side directly above the existing rafters to create a ~ 24"x 1.5" air space from the soffit area to the attic above. I then installed the sheathing on the sleepers and felt/shingles/water and ice shield on top in the traditional way.

This brought our previously uninsulated, unvented (both attic and soffit spaces were plugged with wood) attic space up to R-26 with a nice big air space.

Just though I'd throw that out there.

Here is a pic to help describe what I am talking about

 
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