[Greenbuilding] Polyiso strength on roof

[John Salmen]

Ply sheating wouldn’t qualify as a barrier. Glas mat roofing board would.

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Alan Abrams
Sent: December-07-14 9:55 AM
To: Green Building
Subject: Re: [Greenbuilding] Polyiso strength on roof

 

'nuther factor is the prohibition against exposed plastic foam in the attic. even foil faced polyiso does not fulfill the requirement.

 

-aa




Alan Abrams
certified professional building designer, AIBD
certified passive house consultant, PHIUS

certified passive house builder, PHIUS
cell     202-437-8583
 <mailto:alan at abramsdesignbuild.com> alan at abramsdesignbuild.com
HELICON WORKS  <http://www.heliconworks.com/index2.html> Achitecture and Education

 

On Sun, Dec 7, 2014 at 12:44 PM, Ron Cascio <roncascio at verizon.net> wrote:

Sounds good to me.

 

Ron

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Bill Allen
Sent: Sunday, December 07, 2014 10:52 AM
To: Green Building
Subject: [Greenbuilding] Polyiso strength on roof

 

Hi all

I am about to reroof my 1926 colonial and am looking to also insulate per the BSC "deep energy retrofit" plans consisting of plywood sheathing, 2 layers of 2" polyiso, another layer of plywood, then roofing (in my case, standing seam metal roofing).

The original roof was wooden shingles that are still in place with 2 layers of asphalt on top. Also still in place are the nailers for the wood shingles...roughly 1x2s, 5.5" on center across the rafters.

 

My question is: if I leave the 1x2 nailers in place during the demo can i exclude the first layer of plywood and install the polyiso directly on the nailers? It would then have plywood on top, secured with long screws into the rafters. Less material and less cost.

 

Thanks for any thoughts/comments.

 

 

Sent from my cell phone

< dy>


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