# Would foam be best?



## Windows on Wash (Aug 30, 2011)

Foam to the outside wall is a well accepted practice and does quite a bit to affect the overall wall R-Value by interrupting the thermal bridge of the stud.

If you can go that route, that is the best way and will allow you to use more traditional insulations (i.e. FG, cellulose) with better success.

Wet spray cellulose is fine as long as you follow the manufacturers drying recommendations.

Make sure your details on the foam are spot on and staggered seams.


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## rightit (Mar 5, 2011)

Windows on Wash said:


> Foam to the outside wall is a well accepted practice and does quite a bit to affect the overall wall R-Value by interrupting the thermal bridge of the stud.
> 
> If you can go that route, that is the best way and will allow you to use more traditional insulations (i.e. FG, cellulose) with better success.
> 
> Wet spray cellulose is fine as long as you follow the manufacturers drying recommendations.


So are you saying that foam should be used in addition to other insulations? Is it inadvisable to use only foam on the outside walls? Doing the job right is the priority, but budget is an issue here also. FG might be a bit difficult with the staggered wall, cripples, etc.



> Make sure your details on the foam are spot on and staggered seams.


I'm not quite clear on what you mean here either. Are you referring to coverage? Thank you.


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## Windows on Wash (Aug 30, 2011)

You should use insulation inside the wall spaces as well. Dead air is effectively and insulator but not nearly as effective as FG, Cellulose, etc.

Staggering seams is if you are using multiple layers to the outside surface.

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-install-rigid-foam-sheathing


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## rightit (Mar 5, 2011)

Thanks for the clarification. I suppose I could remove some of the cripples of the original stud wall (20' south wall) to make FG over foam installation more feasible (support is not an issue since there are 2 steel posts and a 12" double header supporting the wall).

If I were to go with the cheaper foam/FG route (as opposed to Foam/Cellulose), would a kraft faced VB facing the living space be neccessary (or even advisable)?


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## Windows on Wash (Aug 30, 2011)

rightit said:


> If I were to go with the cheaper foam/FG route (as opposed to Foam/Cellulose), would a kraft faced VB facing the living space be neccessary (or even advisable)?


No. Don't use any kraft backed insulation regardless.


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## rightit (Mar 5, 2011)

Thanks for your remarks. I trust the opinions of the regulars here and it has helped in my decision making process many times.


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## rightit (Mar 5, 2011)

One more detail...behind the shower. Given that the liner/kerdi/whatever would be akin to a vapor barrier, are there any compensatory steps or different methods required? Normal (not staggered) 2x4 stud wall, blackboard, brick exterior. Foam _and _non-kraftFG, just foam, just FG?


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## rightit (Mar 5, 2011)

Anyone have any thoughts about what method to use when insulating behind the shower and whether the liner presents a vapor barrier issue?


Also, what is the general consensus regarding the home depot foam kits? I'm having trouble generating interest in such a small job.


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## Windows on Wash (Aug 30, 2011)

If you are concerned about the area behind the show, use something like a rockwood in lieu of the fg.

Make sure you kerdi details are spot on and you should be fine.


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## rightit (Mar 5, 2011)

Windows on Wash said:


> If you are concerned about the area behind the show, use something like a rockwood in lieu of the fg.
> 
> Make sure you kerdi details are spot on and you should be fine.


 
I guess I'm not sure what would be best for behind the shower. Is there any reason to be concerned? I had planned on using the heavy liner, sealed, durock because my tile guy prefers durock. But my concern was (durock _or_ kerdi) that the sealed material would create a vapor barrier that might retain moisture. Can I use foam and FG or Rockwool?

And again, given that this is a small job and insulation companies (thus far) interest seems low, any opinions on the DIY foam kits available (i.e., quality, usability)? I found these two, which don't seem all that cheap. The green foam is $609 to handle my Sq footage (around 300 sq ft):

http://www.sprayfoamdirect.com/

http://tigerfoam.com/


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## Windows on Wash (Aug 30, 2011)

I would just use Rockwool and the Kerdi.

If you are worried about it, make sure the foam on those sections of the wall is not a class I vapor retarder so that it can dry to outside.


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## rightit (Mar 5, 2011)

Thanks for your help


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