Add depth to attic ceiling joists for insulation

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Old 08-14-04, 05:32 AM
lmmerritt
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Question Add depth to attic ceiling joists for insulation

I am in the process of renovating attic space into usable space and have 2X6 roof rafters/joists. I want the angled ceiling to be maintained. R-38 insulation is called for in the ceiling. This R-value translates into about 12" thick insulation, what is the best way to add depth to the rafters/joists? Thanks!
 
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Old 08-14-04, 02:12 PM
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Lot of work but just add 2"X6" to the bottom of the roof rafters. Now put 1X4 scabs on each side of them to hold them up to the rafters. Dont for get a ridge vent up there and foam rafter vents so air can get through it all.

ED
 
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Old 08-14-04, 04:41 PM
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Originally Posted by lmmerritt
I am in the process of renovating attic space into usable space and have 2X6 roof rafters/joists. I want the angled ceiling to be maintained. R-38 insulation is called for in the ceiling. This R-value translates into about 12" thick insulation, what is the best way to add depth to the rafters/joists? Thanks!

Simply extending your rafters down to accomodate an R-38 insulation may still not meet your code.

1) code accepts less than 'mandated' insulation requiresments where it is not practical to meet the code and

2) there are multiple ways to achive an R-38 without voluminously extending rafters (for example, 6 inches of 2" polyisocyanurate rigid foam insulation
will create at least an R-39. This may require the extension of the rafters by only 1/4" tp 1 1/4" if at all under proepr circumstances.

3)Where R-38 is required, the requirement may be dropped to R-30 when the roof can be lifted by 10-12 incheas over a "knee wall". Such a construction method is called a "raised heel" type construction method.
 
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Old 09-05-04, 05:02 AM
lmmerritt
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ED,

Thanks for your note. I suspected that adding 2X6's would be the response. I was hoping there was a product that would allow me to avoid adding the joist.

Thanks for your advice!
 
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Old 09-05-04, 05:06 AM
lmmerritt
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Homebild,

Thanks for responding. I was also wondering about that too. I had seen the rigid board at the Home Imp. stores but couldn't find anyone knowlegeable enough about it to give me an answer. I will look into this. I'd like to avoid adding depth as the space in the attic is tight enough.

Thanks again!
 
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Old 09-05-04, 05:09 AM
lmmerritt
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Ed or Homebild,

With rigid board insul. Would I still need the air channel for air movement between the ridge and soffit vents?
 
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