SB: RE: Re: Bales in Floor

[jmark.vanscoter@amd.com]

Sorry for my over simplification of the strength value. But in my defense, when you stand on the foam boards, it is easy to crush the EPS, difficult the XPS. I would guess that there is a greater range of strength in the EPS foam than in the XPS foam.

In regards to the foam in the wings, the big advantage of the foam is in its resistance to compression. To have the same strength without the foam requires a much more rigid skin structure. The foam itself is not strong, but the wing as a foam and fiberglass composite structure is much stronger because of the combination of properties.

Why is EPS "greener"?

Mark V.S. in Austin, TX

P.S. I have just seen too many poorly installed metal roofs (and had to live with some of them) to ignore their strength and weakness. (No pun intended.) The decking and the purlins have been the only reliable and most efficient method of installation.

-----Original Message-----
From: Robert W. Tom [mailto:archilogic@yahoo.ca]
Sent: Wednesday, December 19, 2001 1:09 PM
To: VanScoter, JMark; S.G.Fawthrop@Eklectika.net; strawbale@crest.org
Subject: SB: Re: Bales in Floor


12/17/01 8:18:03 PM, jmark.vanscoter@amd.com wrote:

>If used over a level gravel/sand base (or a thin concrete base) extruded polystyrene sheets 
(XPS) have surprisingly high compressive strength. The EPS (expanded) sheets are very weak.
>
>XPS is used as the base for airplane wings for experimental airplane. They are covered with 
fiberglass and resin, but much of the strength (and all of the shape) is the foam cores.
>
>Of course, this material is highly petrochemical based.

EPS Type II ( white beadboard) isn't all that weak.
It's compression resistance is at least 10 lbs per square inch 
@10% deformation (as compared to XPS ( blue "SM" or pink "CeloFort" brands) 
which has a compression resistance of at least 30 psi @10% deformation.)

10 psi , or 1440 pounds per square foot compression resistance
 is quite adequate  for most residential slabs so long as they are not
bearing any building loads or massive masonry constructions. (ie Check
your loads).

EPS is at least half the cost of XPS for the same R-value and is a lot
more Green.

I question the point about "much of the strength of airplane wings being 
in the foam cores". The tensile and shear strength isn't all that high 
(~60 psi and 35 psi respectively). 
(ie The tensile strength of softwood lumber is  in the neighbouhood 
of 1200 to 2900 psi and shear strength from 95 to 150 psi).

Material placed at the core (ie near the neutral axis)  is the most
ineffective location if strength is what one is after.  Trusses,
pipes, and straws are a good example of this principle and
that's why rebar pins through the bale cores are a waste of 
time and material.

More on insulating floors later perhaps.
(And perhaps also some comments on the plywood AND purlins 
approach to metal roofing.)
 
--- * ---
Rob Tom
Kanata, Ontario, Canada
<ChaffArchiLogic@yahoo.ca>
(winnow the "chaff" spamguard from my edress in your reply)

Please visit http://www.theHungerSite.com daily



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