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GSBN: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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