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renovated attic insulation


pdagosta's Avatar
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Join Date: Dec 2003
Posts: 22

09-17-04, 12:49 PM   #1  
renovated attic insulation

Hi all, I'm a newbie to renovation and insulation, but am a 100% do-it-yourselfer ...

Background:

Attic is now 3 bdrm, 1 bath.
1/2 fully lifted to 4 slope, front have w/ 3 dormers.
Room between framed ceilings and roof is only from 1" at soffit to 4-ft at top ridge. Same with Dormers.

Questions:

Looking at Zip-Code program, my area is recommended for R49 in attic.
Where do I get R49? Most I've seen is R38 (do i add another layer of R11 to it ?). If so, how? Once I staple up the R38, I really don't have access to lay a bed down from above. (ceiling framed with 2 * 6's).

Also, I imagine I only have to insulate exterior walls (R15 in 2*4 )?

Paper side faces interior in all cases, true ? (i've seen pictures on the web of none-faced on exterior walls?) ... need some kind of strips to keep insulation away from roof at soffit sides of the house in order to maintain airflow, recommendations?

Don't know what proper airflow must be from soffitts to ridge on roof, so how much space is needed for airflow (total size of ceiling frame 30' * 50')? There will be a lot of space (4 ft) as the roof approaches the top (vented) ridge, there will be minimal space (1 inch) as the roof approaches the soffit.

Thanks much all !!!

PS> the electical crew on this site were GREAT !!! I was able to do some stuff that even some local contractors were applauding.

 
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09-17-04, 01:33 PM   #2  
Insulation

Posted By: pdagosta Hi all, I'm a newbie to renovation and insulation, but am a 100% do-it-yourselfer ...

Background:

Attic is now 3 bdrm, 1 bath.
1/2 fully lifted to 4 slope, front have w/ 3 dormers.
Room between framed ceilings and roof is only from 1" at soffit to 4-ft at top ridge. Same with Dormers.

Questions:

Looking at Zip-Code program, my area is recommended for R49 in attic.
Where do I get R49? Most I've seen is R38 (do i add another layer of R11 to it ?). If so, how? Once I staple up the R38, I really don't have access to lay a bed down from above. (ceiling framed with 2 * 6's).

Also, I imagine I only have to insulate exterior walls (R15 in 2*4 )?

Paper side faces interior in all cases, true ? (i've seen pictures on the web of none-faced on exterior walls?) ... need some kind of strips to keep insulation away from roof at soffit sides of the house in order to maintain airflow, recommendations?

Don't know what proper airflow must be from soffitts to ridge on roof, so how much space is needed for airflow (total size of ceiling frame 30' * 50')? There will be a lot of space (4 ft) as the roof approaches the top (vented) ridge, there will be minimal space (1 inch) as the roof approaches the soffit.

Thanks much all !!!

PS> the electical crew on this site were GREAT !!! I was able to do some stuff that even some local contractors were applauding.
*********************************************
One method to achieve an R49 is to staple R38 fiberglass to the ceiling joists and then to install another R11 across the top of the R38 perpendicular to it.
But if there is no room, you may need to look at other types of insulation such as rigid foam or sprayed icynene where you can achieve an R49 with a lesser depth of insulation.

For instance, you can achieve an R49 using approximately 7 1/2" of rigid polyisocyanurate insulation as opposed to about 14" of fiberglass.

Same thing for the walls. Since recommended R49 ceilings usually requires at least R25 for walls, you can achieve nearly that level of insulation using rigid foam in the 2x4s.

As afar as airflow goes, you need to maintain a proper airflow from the soffits to above whatever insulation you use in the attic.

This is achieved by stapling rafter vents to the under side of the roof sheathing between rafter to ensure unimpeded airflow.

 
pdagosta's Avatar
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09-24-04, 08:41 PM   #3  
updated question

I think, because my area requires R18 in the exterior walls, that I am going to use 3 1/2 inch R15 AND insulated sheathing. If I combine these 2 in the between the 2 * 4's does the sheathing go in FIRST and then the insulation batts with the vapor barrier facing the room ? ... or ?

 
twelvepole's Avatar
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09-25-04, 02:24 PM   #4  
Vapor retarder in cold climates faces the heated area.

 
Ed Imeduc's Avatar
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09-25-04, 04:48 PM   #5  
... need some kind of strips to keep insulation away from roof at soffit sides of the house in order to maintain airflow, recommendations?
Home depot and Lowes have what you need there in a extruded foam rafter vent. Put it up to the roof then the insulation paper to the room side.

ED

 
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