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

fostertom at clara....uk fostertom at clara....uk
Tue Mar 8 15:54:53 CET 2005

Hi guys

Ok, if even 40cm is too thick, that's a problem. But if there's plenty
of space, why not use two thicknesses of bales, total 90cm (in Britain
the official terminology, decided when we went metric in the 1970s, is
900, meaning 900mm, or 0.9m, never 90cm). Or yes, jumbo bales.

I'm starting on a project for a community hall in Dorset of 190m2 plus
bar and ancillary spaces, of straw bales and engineered pine poles, in 2
chambers, one round and one elliptical with reciprocal roofs, separated
by a moveable soundproof partition, to be self-built by the community.
It has to have very good noise containment, better than the 45dB that a
single bale wall seems to give. So we're looking at either 2 thicknesses
of bales, maybe with a cavity between, or one thickness but with very
thick daub (clay) internal render - perhaps 8cm thick. The double
thickness will incidentally give fabulous insulation. It will also
provide a place for an airtight but vapour-transparent breather
membrane, between the layers, to link up with other details to eliminate
accidental airchange, which becomes the biggest heat loss. We have to
have very large sealed-system heat recovery artificial ventilation, as
natural ventilation would let all the noise out. Plus special glazing
and doors. With high efficiency electric lighting, plus lots of dancing
bodies, it looks like no heating system will be needed - could even
create a nett heat gain, to be used elsewhere on the site.

The challenge is to make it light and airy, not like a bunker! I would
welcome comments, experience and test results that would help with this

All the best

Tom Foster B.Sc.(Architecture) AECB
Tom Foster Architecture

-----Original Message-----
From: strawbale-admin at amper....muni.cz
[mailto:strawbale-admin at amper....muni.cz] On Behalf Of Rene Dalmeijer
Sent: 08 March 2005 12:18
To: strawbale at amper....muni.cz
Cc: Werner Schmidt
Subject: [Strawbale]Re: Strawbale digest, Vol 1 #474 - 7 msgs


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
> 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.)

    European strawbale building discussion list

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