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

Rene Dalmeijer rene.dalmeijer at hetnet...
Tue Mar 8 13:17:46 CET 2005


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 

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 at amper....muni.cz wrote:

> Date: Tue, 8 Mar 2005 01:05:02 +0100 (CET)
> From: Jan Hollan <jhollan at amper....muni.cz>
> To: strawbale at amper....muni.cz
> Subject: [Strawbale]Measured heat flux through a real wall/ceiling
> Reply-To: strawbale at 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.)

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