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Attic Insulation


Maddie's Avatar
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02-06-02, 12:10 PM   #1  
Maddie
Attic Insulation

I want to insulate my unfinished attic that will eventually be renovated into living space with cathedral ceilings, it is approximately 1000 sq. feet. The attic currently has no insulation. The rafters are only 2x6. Can I use rigid boards and how do they a fix to the rafters? What kind would you recommend...I would rather not have to add furring (sp?) strips to accommodate fiberglass batts. I assume I need rafter vents for air circulation. Will I need a vapor barrier covering the foam boards? Is this something I can do before knowing how I plan to renovate the attic? Finally, how much can I expect the materials to cost? I live in Boston where the recommended R value is anywhere from 30 to 38. Thank you for your help

 
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02-06-02, 01:20 PM   #2  
Insulman
If your 2 x 6's are flat and the drywall is already installed. Then I would suggest you install the fiberglass batts, as long as you place them with the paper facing the drywall there is no need to staple them in place. Then you can use the same material again when you reframe your Cathedral ceiling assuming of course they are going to be on the same centers 16" or 24" ? If your going to frame your Cathedral ceiling with 2" x 12"s then you can use standard R-30 fiberglass batts which are approx 10" thick or you can use high density R-38 which is only 10 1/4" thick.. If your going to use 2" x 10"'s then I would recommend you use R-30 high density batts which are only 8 1/4 " thick..

Going the batt route should be less expensive per R value than using rigid foam board.

Good Luck

Jim

 
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02-06-02, 01:41 PM   #3  
Maddie
Hello Jim

Thank you for your reply. My attic does not have any drywall hung at this point and is merely open rafters. I cannot use fiberglass batts at R-30 or R-38 values on 2x6 rafters can I without adding furring strips? Thanks...

Maddie

 
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02-06-02, 01:59 PM   #4  
Insulman
If you have attic space above the 2x6's and not a flat roof system then yes you can use insulation thicker than the 2x6s. If you have soffit vents be sure to install styrofoam baffles prior to installing the fiberglass. I would reccomend 1 in each truss space, allowing air to flow between the soffit area and the attic.

Fiberglass insulation for ceiling areas is a full 16 or 24 inch width, once it clears the 2x6s (when properly installed) it will come together above them.

If your temporarily insulating and plan to build your floor on the future addtion right on top of the 2x6's then just use R-19 6" thick in the areas where you plan to lay a floor above. The other areas I would install the higher R-value insulation. What you will have to consider when building up the 2nd floor is if you wish to leave the new insulation in place. Once you have conditioned the 2nd floor with heat and air the insulation between the 2 floors the only benefit of the insualtion will be sound transfer between floors.

Good Luck

Jim

 
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