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Insulating open beam vaulted ceilings
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posted
My house has a low slant open beam vaulted ceiling. It has a composition shingle roof layed on tongue and groove 1 X 6 boards that are visible inside the house. These are layed on 4 X 6 (3 1/2 X 5 1/2 inches finished) rafters that are also exposed.

I plan to install overhead can lighting and insulate, then sheetrock and texture the finished ceiling. This is planned for the entire home which is roughly 1100 sq. ft.

Since I only have 5 1/2 inches of thickness to work with, what is my best insulation option? According to guidelines, I see my ceiling should have a R49 insulation value here in Northern California. How can I possibly obtain even close to this R value with the construction I have?
 
Posts: 3 | Registered: 20 June 2006Reply With QuoteReport This Post
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The only way I can think of would be to use EPS (expanded polystyrene) which gives you a R-Value of 3.75 per inch thick. You can order them in panels, pre-groove to match your rafters, in any thickeness you need, then use long screws with washer to fastened the EPS to your rafters(eps as no weight to it), and I do beleive that they can apply texture ceiling directly to the EPS. In you case, you said that you need R49...Using EPS you would need roughly 13 inches, but since the true value of EPS is higher(because your raping your rafter, you would probably get away with less)......keep in mind to ask about the codes in your area, ask about the texture ceiling, if they can apply it on EPS(I know they can apply stucco directly to it)...most important, regardless of what your using, keep an air space between you insulation and the board.
ps: you will have to some research for an EPS supplyer, you won't find that on the shelf at Home Depot, at least not in Canada.
Good luck, and let me know how that worked!
 
Posts: 17 | Location: Ontario | Registered: 22 February 2006Reply With QuoteReport This Post
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If I use the EPS, I will only get R18 value (leaving a 1/2 inch air space, since I only have 5 1/2 inches to work with). I had figured on using R19 fiberglass, which I can use in my 5 1/2 inch ceiling space, coupled with reflective insulation. This will give me roughly R35 or better, but cost me approximately $1000 for an 1100 sq ft installation.

I am not real knowlegable on insulation, and I thank you for your suggestion. I was hoping someone could come up with a better idea than I have Frowner

Any better ideas? Is my idea feasible?
 
Posts: 3 | Registered: 20 June 2006Reply With QuoteReport This Post
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I have a similar situation. My house was built in 1955... an A-frame roof (4/12 slope) with open beams/no insulation... i.e., roof shingles are nailed to boards that form the interior roof. I too would like to install canned lights... and ideally I would install drywall 5-1/2 to 6 inches below, with insulation above the celing. My question is not only which insulation to use, but also, does this method provde adequate venting in the summer time? I live near the ocean in San Diego. While it may get hot during the day, it cools dramatically in the eve. My theory is, without ventilation, the insulation will do well as a hea barrier by day, but work like a heat trap at night without venting, preventing the house from colling down. Any advice would be appreciated. I understand that exterior/roof mounted insulation provides a lower R value, but has better ventilation. But the roof insulation method is pricey and I still want canned lights...something I can only get if I drop a ceiling.

Thanks much, Richard
 
Posts: 1 | Location: San Diego, CA | Registered: 04 July 2006Reply With QuoteReport This Post
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When you insulate do NOT forget to provide venting at the peak of the roof (ridge vents that can have shingles nailed to them). Also you should have vents at the overhang to allow air to go up under the roof to lower the heat by venting it at the peak of the roof. That should make your roof covering last much longer because the heat will build up without proper venting. Fix one problem, find 2 more. Right?
 
Posts: 4 | Location: Washington, Il. | Registered: 05 July 2006Reply With QuoteReport This Post
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quote:
Originally posted by T. Malcom:
. . .you should have vents at the overhang to allow air to go up under the roof to lower the heat by venting it at the peak of the roof.


That's a great idea, but what if my house doesn't have an overhang? Actually, in my situation, it's my garage that I'm insulating, but it doesn't have soffits either. Any suggestions?
 
Posts: 1 | Registered: 07 July 2006Reply With QuoteReport This Post
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I looked at an old cabin the other day. The homeowner bought it, removed the interior cieling to find tongue and groove 1x6 that are held up by real log rafters of various thickness. They really liked this look but want to replace 1x6 with new 1x6 tongue and groove and keep rafters. Problem is the cabin has no soffit to ridge ventilation or insulation. They plan on living in it year round and need to heat it, but to keep this look and provide proper ventilation as well as insulation I dont know of any product that could be applied with out raising the exterior height of the roof.
 
Posts: 1 | Location: New Buffalo, MI | Registered: 01 August 2006Reply With QuoteReport This Post
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