[Greenbuilding] Basement EPS with plywood (acceptable)

Alan Abrams alan at abramsdesignbuild.com
Sat Jul 13 14:05:16 MDT 2013


John--If I understand your comments, the big objection to Roxul is in the
potential for outgassing; secondarily, a question about its structural
capacity.  I agree that any unusual load should be carried through the
floor system to proper bearing--or--in the case of a bearing wall with
modest loading, perhaps that could be supported by a strip of high density
EPS (aka Geofoam) in order to minimize thermal bridging.  With regard to
the outgassing issue, my sense (not having tried this yet)  would be to
trust taping the seams of the subfloor, and taping the edges to the
perimeter walls.  Lastly, a double staggered lap of subfloor ought to
bridge local deficiencies in the insulation itself--unless this stuff is
grossly incompetent.

On the other hand, I probably wouldn't exceed using a single three inch
thick panel--given its "off label" application.  Not until someone braver
has tried it with success.

For years, wiser members of this listserve have been beating the drum to
wean ourselves from plast-ecch foam.  Alex Wilson and now even PHIUS is
making the same case.  The rationale has been slow to penetrate this thick
skull, but it is beginning to seep through into the void.

-AA

On Sat, Jul 13, 2013 at 12:50 PM, John Salmen <terrain at shaw.ca> wrote:

> Tried that. The fiber industry uses formaldehyde as the binder to achieve
> densities. Higher densities more resin. Roxul states the urea is cured with
> little potential for offgassing. Technically I am not sure what they are
> talking about as curing reduces strength and ultimately density. The use of
> formaldehyde is generally a compromise between emissions and strength. The
> residential ‘comfort board’ I think reflects that compromise with a density
> of only 745 psf. EPS type 1 (the lowest density) is about double that. I
> would be concerned about using it as long term structure (under partition
> walls, etc.). ****
>
> ** **
>
> My experience with the product was that it was,  dusty, noxious and worst
> of all inconsistent in density (roxul) – imagine a beehive hairdo. You can
> crush the board with your foot or punch your fist through - so it was
> difficult to work with as a board stock.****
>
> ** **
>
> I could see using the higher density commercial roofing boards but then
> would be concerned about offgassing.****
>
> ** **
>
> *From:* Greenbuilding [mailto:
> greenbuilding-bounces at lists.bioenergylists.org] *On Behalf Of *Alan Abrams
> *Sent:* July-13-13 6:26 AM
> *To:* Green Building
> *Subject:* Re: [Greenbuilding] Basement EPS with plywood (acceptable)****
>
> ** **
>
> because XPS has a significantly higher global warming potential than EPS,
> I'd prefer the latter--even at somewhat lower R-value per unit of
> thickness.  Others on this list (John Salmen) have written extensively
> about using adhesives instead of mechanical fasteners to connect the
> components.  ****
>
> ** **
>
> it raises another idea--to use rigid mineral fiber instead of foam.  Roxul
> comfort board is rated at R-4 per inch, and is said to compress only 10%
> under 743 LBs per SF.  dunno how that extrapolates to ordinary live loads,
> but it still suggests a double, staggered layer of plywood, mechanically
> fastened.  many other advantages, including dimensional stability, fire,
> rot, and pest resistance, high permeability, and low embodied energy.
>
> Alan Abrams****
>
> ** **
>
> On Fri, Jul 12, 2013 at 10:55 PM, Sam Ewbank <g.l.ewbank at gmail.com> wrote:
> ****
>
> From the green building archives.  A similar application to what you are
> looking to do but with the suggestion of using 1.5" EPS****
>
> ** **
>
>
> http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/2012-April/003703.html
> ****
>
> ** **
>
> ** **
>
> On Fri, Jul 12, 2013 at 9:52 PM, John O'Brien <john at boardom.ca> wrote:****
>
> Friend is doing some work, looking to put down 1" EPS, with floating
> plywood, tapcon'd down, followed by some floating laminate.
>
> Would this be considered an acceptable base, or would it be beneficial
> to bump up to XPS or run a double layer of 1/2" ply staggered for more
> point load compression protection?
>
> Cheers,
>
> J****
>
> ** **
>
>  ****
>
>  ****
>
> Sam Ewbank****
>
> ** **
>
>
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-- 
Alan Abrams*
**certified professional building designer, AIBD
certified passive house consultant, PHIUS*
*certified passive house builder, PHIUS**
*Abrams Design Build LLC
*sustainable design for intentional living*
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com
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