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[Strawbale]Re: Strawbale digest, Vol 1 #474 - 7 msgs

Jan,
Recently there was quite an extensive discussion on the specific heat transfer value for plastered (air tight) SB walls. The final consensus is that in nearly every case a value of at least 0.08 W/mK is achievable leading to a rough value of around 0.18 W/m^2K which is a little above what you would like to have.
Some of the measurements have given figures of 0.045 but I think these are not realistic. I expect though that a well executed dense (>120kg/m^3) SB wall could achieve a value in the region of what you seek.
I agree that a Low U value is of paramount importance to achieve the holly grail of a passive house but it surely is not the only ingredient required. Granted SB is not the best performing insulation material around but where can you get a better ecological combination of building block and insulation then SB?
Werner Schmidt, CH when striving to achieve passive house or even better stumbled on jumbo strawbales. He has since then made quite a few effective designs using SB he is a keen advocate. 
On Mar 8, 2005, at 07:36, strawbale-request@amper....muni.cz wrote:


Date: Tue, 8 Mar 2005 01:05:02 +0100 (CET)
From: Jan Hollan <jhollan@amper....muni.cz>
To: strawbale@amper....muni.cz
Subject: [Strawbale]Measured heat flux through a real wall/ceiling
Reply-To: strawbale@amper....muni.cz
I wonder very much, if anybody has heat consumption data for any strawbale house already, or any measured heat flux data for a wall with 40 cm bales 
and a 20 K or even larger temperature difference.  (Unfortunately, our
nice installation, a heat storage tank for a solar system, is still
unsuitable for measuring that, being not air-tight and behaving partly
like a chimney...)

As I wrote earlier, I still doubt that convection does not play a large
role inside bales. I hope that at least inside heavy giant bales it might be minor. But even about this I'm not so sure (I admit it ceases to be a 
large problem with 90 cm thick layers).
The question is important when we are to be sure that 40 cm bales (e.g., over 90 kg/m3) will really give U of below 0.12, needed mostly for passive 
houses. Not everywhere more space is available (we have to build a
house where even 40 cm will be a bit of a problem).

Will somebody present any answer on this at the
http://passivhaustagung.de? (I'll be there with another topic, a poster on 
windows with Al-layers.)


Rene