# Unique attic situation and need assistance



## Gary in WA (Mar 11, 2009)

If the foam is fastened and canned foam air sealed to the cold in winter side of the wall. After installation, add some f.b. rips to cover the truss cord/struts over-lapping the in-between f.b. pieces some for a thermal break from the cold attic. Add ignition barrier if required on f.b. per local AHJ.

Gary


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## mystic_cobra (Apr 18, 2011)

Gary-
Thanks for the reply. So, I like the rigid foam combined with canned spray foam idea for the gaps. 
The second suggestion, I'm not sure I understood. Are you saying to cut long strips of the rigid foam board (say 5-6" wide) and lay them as another layer over top of the truss chords to cover the rigid foam edges where they meet the chords?
Do I need to use some kind of special tape to cover the seams or will the overlap be sufficient to seal out the air?


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## Gary in WA (Mar 11, 2009)

Check w. AHJ on covering the f.b. with ignition barrier or not, may let you get by with foil-faced rigid board or none at all, depends on local Ins. and conditions in attic; http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/14816/kw/attic%20foam%20thermal%20barrier/session/L3RpbWUvMTMxODYwMjg4MS9zaWQvKkNueDl5R2s%3D

*4.2*---- http://commercial.owenscorning.com/assets/0/144/172/174/5deb06d2-43b4-44b2-b4ec-20579af27e5d.pdf 

Then caulk perimeter under the over-pieces and foil tape the exposed edges to protect from flames. Need it as air-tight as possible.

Gary


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## mystic_cobra (Apr 18, 2011)

Is AHJ a person?
Looks like the Dow link is bad. 
I'm pretty sure the rigid foam board at my local home depot has foil on both sides but I guess all the edges and seams would need foil tape, right?


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## Gary in WA (Mar 11, 2009)

Always good to check with Authority Having Jurisdiction. I changed the links, thanks.

Gary


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## mystic_cobra (Apr 18, 2011)

I spoke with a code official at my county office and he said that fire proofing is not required on the attic side of that wall. 

I'm going to take Gary's advice and use the foil covered foam board, seal all the gaps with spray foam, and the edges of the foam board with metal tape. 

thanks!


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