[Strawbale] Convection in SB walls

forum at lamaisonenpaille... forum at lamaisonenpaille...
Wed Dec 8 21:58:28 CET 2010

Some of us EuroBaleHeads are indeed aware of the test you mention ;-)  . 
We talked about it with 'Murrican' David Eisenberg during the last 
European gathering in Belgium as he was involved in that particular 
testing. I understood that there was a considerable space between the 
bales and the gypsum board and that he believes that this air-space 
increases tremendously the convection that is common in fibrous 
insulation materials. If I understood him correctly he does not consider 
it a problem to put a bale tightly agains a panel but strongly advices 
against an airspace between the bales and a panel.

Herbert, has any testing been done on your finished panels or is 'your' 
R value based on a theoretical accumulation of the different matérials 
you use?


> 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.
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