# Isoboard and exterior insulation on roof



## Tigertalk (22 d ago)

First post so my apologies and please redirect if needed. 
I’m searching on this site but unable to find threads on solving exterior insulation for a shingle roof utilizing isoboard/foam. I’m approaching a garage conversion (400sqft) where I’m hoping to retain the vintage wooden ceiling(which is just the underside of roof deck) rafters, and beams exposed rather than enclosed with spray foam or roll.

My thoughts were to use isoboard and insulate from the top under the shingles but concerns were how to get an increase in r-value over 20. Is it possible? I’m in the southeast so it’s going to get hot and humid in summer as well as somewhat cold in winter. Planning on installing a mini split unit to heat/cool.

Any recommendations would be much appreciated.


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## Deerfly (Mar 14, 2021)

Look into Atlas AcFoam nail base. Should point you in the right direction for what your looking to do. There are several manufacturers that make a product like this. 
Gaf, Mulehide, Firestone I believe are a few others that make a similar product.


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