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GSBN: Digest for 11/5/02



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-> Euro-pee'ins
     by "Rob Tom" rw_tom@...


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Date: 5 Nov 2002 15:47:37 -0600
From: "Rob Tom" rw_tom@...
Subject: Euro-pee'ins


I'm not sure who to thank for the Austrian numbers(appended below) that 
were, I think, forwarded by Joyce ("thengya" nonetheless), but I do have 
some comments:

First of all, the units(W/mK) of the quantity described as "Lambda" at the 
opening of the message appear to correspond to the units for "Thermal 
Conductivity" , or the inverse of "Thermal Resistivity".

For the benefit of the Murricans on this List who often seem to be 
SIU-challenged: For thermal conductivity, to convert from  SIU to Imperial 
(Murrican) units:

SIU (watts/metre*degC)  x   6.9348  =  Imperial Units ( 
(Btu*inch)/(hr*ft^2*degF) )

Taking a look at the table entitled "Comparison of Values", the units listed 
for "Lambda" (which previously seemed to be defined as being "conductivity") 
but actually appear to be the units for thermal conductance (ie (W/m^2*degC) 
[or what is later described as being "Warmedurchgangskoeffizient"], which of 
course, makes no sense for the value shown (the units being nonsensical that 
is, not the name, which I like, a lot).

Further, assuming that the value shown for straw (ie 0.045 W/m*K) does in 
fact, represent thermal conductivity rather than conductance, then it 
appears to be overly optimistic (ie R-3.2 per inch when converted to thermal 
resistivity).

I'm not all that clear on what the quantity "LRTr10" is but the value listed 
(0.038 W/m*K ?) if representing thermal conductivity at some different 
moisture content (presumably drier than for Lambda) it appears to be even 
more overly optimistic at R-3.8 per inch.

I noted that the density of the Austrian straw ( 100 kg/m^3 or 6.2 lbs/ft^3) 
seems to be a bit on the light side for building bales.

I think that perhaps the Austrians should talk to the French, as mon ami 
Andre de Bouter tells me that for a wall thickness of 490mm (or ~19.3 
inches, plaster included (ie two-string bales)) the French use a value for 
"Resistance Thermique" of 6 m^2*degC/W , (or R-1.96 per inch, or a Lambda 
value of 0.074), a value which is significantly more conservative than that 
of the Austrians, and probably closer to the reality that will be achieved 
in actual SB walls existing outside of laboratory conditions.


As to the "PEI" (which I'm assuming are the embodied energy numbers), I 
haven't gotten around to converting them to the more typical units of 
MJ/tonne or J/kg or BTUs/lb (ie energy per unit weight) instead of the units 
listed ( ie energy per unit volume)in order to anal-yse the Austrian data 
but at this point (given all of the above), I must say that I am somewhat 
sceptical as to the usefullness of the summary beyond
being a very rough, subjective comparison.

Of course, one could just forget about all this number-nerd stuff and just 
say

" Eh-h-h-h, "So what?" if the Euro-pee'ins seem to have a discrepancy of 
almost 100% in their thermal resistivity numbers ? We can still be friends, 
right ?"

  --- * ---
Robert W. Tom
Kanata, Ontario, Canada
rw_tom@...

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






>Date: 4 Nov 2002 13:43:02 -0600
>From: jc10508@...

[snipped for brevity]

>(European) terms:
>You know: Lambda L= W/mK

>so each organic material has to have a 20% addiction to
>LRTr10 (new after CEN = LNTr10):

>insulation value (Lambda) for a dry (tr)material at a temperature of 
>10#161#C (for 1m, so L never depends on thickness of wall)

k= W/m2K (Warmedurchgangskoeffizient, depends on the thickness of the wall

>PEI: amount of energy to manufacture/transport/.. a matarial

>1) comparison of values
>
>material        L      LRtr10         raw-weight    included prod-energy
>             (W/m2K)                     kg/m3           (PEI: kWh/m3)
>
>strawbales   0,045     0,038            100             5-30
>                        (as proved in our official tests in Austria)


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