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Hi Beatrice,<br>
<br>
<div class="moz-cite-prefix"><i>On 2/20/24 11:18 a.m., Beatrice
Dohrn via Greenbuilding wrote:<br>
<br>
</i>
<div dir="ltr" data-setdir="false"><i>Sorry, I guess I was
unclear. I am talking about an outdoor deck. So from inside
up presently: <br>
</i></div>
<i>Sheetrock, rafters, plywood, 7" polyiso, plywood, epdm,
sleepers, decking. I am looking to replace the insulation
portion. Perhaps board rockwool? It's a faswall house, fyi. </i></div>
<br>
To be clear, this is a structural issue, not a thermal issue; ie.
the polysio has degraded to the extent that it no longer supports
the deck. If so, you could use any number of structural boards like
the one Norbert suggested or perhaps this Rockwool product
(<a class="moz-txt-link-freetext" href="https://www.rockwool.com/north-america/products-and-applications/products/comfortboard-110/#Specifications&Sizes">https://www.rockwool.com/north-america/products-and-applications/products/comfortboard-110/#Specifications&Sizes</a>
).<br>
<br>
If the polyiso is structurally sound and will likely remain so, can
you remove the drywall and insulate from below, using a closed cell
spray polyurethane foam? I think the closed cell foam is about
R6/inch and should meet the thermal, air and vapour code
requirements of your area. It may be cheaper than removing the
polyiso, plywood, epdm, sleepers and decking.<br>
<br>
All the best,<br>
Peter<br>
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