Install over radiant barrier

Candace Harrison
4/22/2011
I currently have an existing wood shingle roof with a cathedral ceiling. The shingles are installed from what I can tell over 1/2" fesco board over 1x2's over building paper over 1x t&g decking which spans between wood ceiling joists. A roofing contractor I am looking at using has proposed taking off the wood singles only down to the fesco board, leaving the fesco board in place and building on top of that with: metal shingles over building paper over radiant barrier over 2x2's infilled with 1" of rigid insulation, leaving a 1/2" air space (with a ridge vent and an eave vent at the bottom) over the existing fesco board. My questions: - Doesn't the air space want to be directly below the metal roof above the OSB? Or is it ok to have it below the OSB? - Does the radiant barrier go foil side down or up? - What is the point of leaving the existing fesco board in place and battens in place? My goal is increase the R-value of the assembly but it doesn't seem to me that the fesco is worth the R-value to leave in place. Intuitively it seems like you would want to remove all down to the deck and build up from there. I may then want to start witth 2x4's to get 3" of rigid for a better R value with a 1/2" air space. - I goal would be to achieve an R-30. Thoughts? Thanks!!
Todd Miller
Classic Products, Inc.
4/29/2011
I am having a tough time figuring out exactly what is going on and what is proposed.Air spaces can be effective located just about anywhere. The same with ventilation. In regard to radiant barrier, the shiny side should face an airspace. I hope this helps. Feel free to call me at 1-800-543-8938 ext 201 All best.
Info @windowsonwashington.net
An informed customer is our best customer.
5/2/2011
Radiant barriers require an air space to function. If there is not one, all you have applied is a conductive foil.

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