[Strawbale] OSB in detail
ArchiLogic at yahoo...
Wed Dec 8 19:53:32 CET 2010
On Tue, 07 Dec 2010 16:12:55 -0500, Derek Roff <derek at unm...> wrote:
<snipped,mangled & pasted>
( for full text of message, see:
> --On Tuesday, December 7, 2010 8:06 PM +0100 asbn <asbn at baubiologie...>
>> I would like to have a completely natural structural board instead of
>> OSB, but we didn't find a board with the same advantages and a
>> similar price.
> This described sequence of motivation, analysis, and product selection
> is at the root of so many of our problems in the world.
> I don't think it is possible to be active in the world ofgreen building,
> and also be free of compromises with companies andproducts
Which brings us back to the original point which started the thread that
started this thread:
"OSB or Not ?"
It is entirely possible to build SB walls that are structurally sound and
air-tight without utilising OSB.
In fact, SB walls built using wet-applied plaster instead of OSB can be
better structurally, will almost always have a significantly better
thermal resistance value (see note below), are less difficult to make
air-tight and depending upon the type and thickness of the plaster used,
will be clad in a skin that is more vapour permeable.
OTOH, most plasters will not have any traces of noxious chemicals like
phenols, formaldehydes, diphenylmethanes, diisocyanates etc. that are
commonly found in OSB.
(For those who aren't already aware, "Material Safety Data Sheets" (MSDS)
are available for all manufactured products (ie simply Google "MSDS
Oriented Strand Board" in this instance) and they list & describe all of
the potential health hazards associated with that product.)
It seems that including OSB in a SB wall creates more problems than it
This is the Note Below
I don't know if EuroBaleHeads are aware of the first set of thermal
resistance tests that were performed on SB wall panels at the Oak Ridge
National Laboratory (ORNL) back in the previous millennium which resulted
in alarmingly low thermal resistance values for the SB walls tested.
I forget what the actual test results were (something like R-10
ft^2*hr*degF/Btu (or RSI -1.76 m^2*degC/W in metric units) or less if I
recall correctly ? (Hoping someone will correct me with the actual number)
... but I do recall that it was lower than the thermal resistance of a
conventional wood-framed/fibre batt-insulated wall using skinny 2x4 (38 x
89 mm) studs.
I also remember that the reason for the disgustingly low thermal
resistance value of those first SB test wall panels was attributed to
their being clad with gypsum board sheathing rather than wet-applied
plaster and that since the board sheathing could not conform to the
irregular surface of the SB, allowed air movement to occur at the
cladding/SB interface so that thermal resistance-lowering convection
currents occurred within the SB wall.
I suspect that the identical process would occur when OSB is substituted
for gypsum board sheathing.
=== * ===
Kanata, Ontario, Canada
< A r c h i L o g i c at Y a h o o dot c a >
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