[Greenbuilding] Polyiso strength on roof

[Steve Houlihan]

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 <mailto:alan at abramsdesignbuild.com>
> HELICON WORKS /Achitecture and Education/ 
> <http://www.heliconworks.com/index2.html>
>
> On Sun, Dec 7, 2014 at 12:44 PM, Ron Cascio <roncascio at verizon.net 
> <mailto:roncascio at verizon.net>> wrote:
>
> Sounds good to me.
>
> Ron
>
> *From:*Greenbuilding 
> [mailto:greenbuilding-bounces at lists.bioenergylists.org 
> <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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