[Greenbuilding] Polyiso strength on roof

[Bill Allen]

Steve,
I am suggesting a sip type assembly only without the bottom plywood.  The insulation will rest on the 1x2 nailers. This is the inverse of what you discribed.


Sent from my cell phone


-------- Original message --------
From: Steve Houlihan <sho11 at comcast.net> 
Date:12/07/2014  1:28 PM  (GMT-05:00) 
To: greenbuilding at lists.bioenergylists.org 
Cc:  
Subject: Re: [Greenbuilding] Polyiso strength on roof 

There are many thousands of roofs out there with a layer of plywood then rigid foam above.  I'm under one right now.  I have never seen the Building Department to have a problem with this.  I suggest you check with your local jurisdiction to be sure.
I don't see any difference to this from using SIPS on the roof.

Steve Houlihan

On 12/7/14 10:08 AM, John Salmen wrote:
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
alan at abramsdesignbuild.com
HELICON WORKS 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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