[Greenbuilding] Basement EPS with plywood (acceptable)

John Salmen terrain at shaw.ca
Sat Jul 13 16:01:35 MDT 2013

Not sure to be honest. 


Formaldehyde is not the worst carcinogenic chemical in most homes so its
about trying not to not add more to the mix when avoidable. Inhalable fibres
and dusts are a legitimate concern. But mostly it was the sense that it was
not well suited to the application in comparison to eps and it is truly
noxious to work with. I've not seen it used in sips other than commercial
panels nor is it used in geo fill. Its basically a compressible fibre made
stiff with a glue that may or may not have good water resistance depending
on what was used.


As for plasteech. In building most every material has an inherent toxicity.
Both for builders and end users. It remains for us to use material wisely
but remain critical and keep gathering information - not just beat drums.
Rockwool is implicated in workplace cancers and workplace exposures to
rockwool dust/fibres exceeds glass wool exposures for some reason
(dustier?).  Rockwool can have a resin content of 5% of its weight.  The
styrene content of polystyrene is .1% by weight and polystyrene is 2% by
volume of eps. There is also radon. I mention these things only to say that
there are no simple directives.


The real culprit in building is pvc as it is the cheapest and most toxic
plastic out there on the ranking. A good example is waste and drain systems.
Perforated pvc pipe for drainage probably has more plastic content than an
eps wrap of a house. It is hard to get builders to substitute with
polyethylene because it is not considered standard or good practice - in
reality you can eliminate piping altogether and simply use washed rock and
that is approvable (though most inspectors would argue). ABS plastic for dwv
is more benign than pvc yet in the US pvc has become the standard. Is anyone
still using copper in water supply systems?


End of rant





From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of Alan Abrams
Sent: July-13-13 1:05 PM
To: Green Building
Subject: Re: [Greenbuilding] Basement EPS with plywood (acceptable)


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


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.   



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





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?






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
 <mailto:alan at abramsdesignbuild.com> alan at abramsdesignbuild.com
 <http://www.abramsdesignbuild.com/> www.abramsdesignbuild.com

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