# Insulating unvented attic w/ 2x4 rafters?



## rion.martin

Pictures of what I'm working with

Attic space on the side of the living space









Upper attic:









Where rafter meets the header for the outside wall









Space between bottom segment and upper segment of attic


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## Seattle2k

have you considered Structural Insulated Panels for the underside of the roof?
http://www.doityourself.com/forum/i...ractices-insulating-cathedral-ceilings.html#b


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## Windows on Wash

From those pictures you have a mixture of conditioned and un-conditioned. You need to establish what you want and your insulation plans will be dictated by that.


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## rion.martin

Since this post I have insulated the knee walls with r13 batts which has helped quite a bit but the space is still not as comfortable as I would like. 

Considering the amount of extra work to create a proper ventilation system I would rather create a conditioned attic space. However, from what I've seen this can really only be accomplished with spray foam? I'm not sure if that option is immediately within my budget, maybe next year. 

Seattle2k, I've considered using foam board on the underside of the rafters, however that link seems to only discuss using it on top of the sheathing? The problem I see with attaching foam board to the rafters is that I would need to put an ignition barrier on underneath it as well. 

The other thing I have considered is putting up a radiant barrier on the underside of the rafters. In the attic space parallel to the living space the radiant barrier would have the added benefit of keeping the batts in place between the rafters. 

Thoughts?


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## liquidbeef

rion.martin said:


> Since this post I have insulated the knee walls with r13 batts which has helped quite a bit but the space is still not as comfortable as I would like.
> 
> Considering the amount of extra work to create a proper ventilation system I would rather create a conditioned attic space. However, from what I've seen this can really only be accomplished with spray foam? I'm not sure if that option is immediately within my budget, maybe next year.
> 
> Seattle2k, I've considered using foam board on the underside of the rafters, however that link seems to only discuss using it on top of the sheathing? The problem I see with attaching foam board to the rafters is that I would need to put an ignition barrier on underneath it as well.
> 
> The other thing I have considered is putting up a radiant barrier on the underside of the rafters. In the attic space parallel to the living space the radiant barrier would have the added benefit of keeping the batts in place between the rafters.
> 
> Thoughts?


Hey there! Any great strides in the last two years? I'm in exactly the same situation as yourself. Would love to hear what you wound up doing.

My house has an addition built perpendicular to either side of the room we're giving a cathedral ceiling, so now only half of one side of the cathedral ceiling sits on an exterior wall. Should I even bother with a ridge vent if only 25% of the ceiling would benefit from soffit vents? I'd love to go closed cell foam (I think?) but I don't have too much money to spend on it right now.

I am leaning toward 24" Reflectix reflective insulation between each 2x4 rafter to act as a vapor barrier and 2" rigid insulation foam, held in place with Great Stuff Pro. 

Thoughts?


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## Windows on Wash

Pictures.

Not a fan of the radiant barriers. They are cheesy science and can cause more problems than fix.


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