[Strawbale] convection and humidity in straw bale walls

[paul sheraton]

Hi Michaell

when a Canadian says cool, do they mean -20 and snow drifts ? :)

Im not a scientist either but I would have thought that for a convection 
current to operate you would need a fair sized  air space for the 
circulation to take effect. Double glazed windows can go up to 22 mm cavity 
gap before convection begins to become a problem.  I could see there might 
be a problem if you had a bale wall with an external cladding of wood to 
protect it and there exists a big gap between the wood cladding and bale 
wall (aswell as a big fire risk from a chimney effect) Porous iinsulators 
like straw bales could easily have their insulative value eroded if there is 
a  convective current running over its surface like this. Is it not 
conventional thinking that putting ANY barriers inside a bale wall will 
create more problems unless done very carefully.  Just so thoughts from 
France.

  A queation to Canadian SB builders or any one buildig in similar climates. 
I bought Chris Macwoods details book in which all the designs pay particular 
attention to having a vapour checkinstalled. This might be a stupid question 
but is not possible to build a straw bale wall that doesnt need the vapour 
check? does anyone know of SB buildings in Canada being built without a 
vapour check? where will the condensation be, on the interstitial gap behind 
the external render?

regards

Paul


>From: "Michael lough" <michaelklough at sympatico...>
>Reply-To: mkl18 at pobox...,        European strawbale building 
>discussions<strawbale at amper....muni.cz>
>To: strawbale at amper....muni.cz
>Subject: [Strawbale] convection and humidity in straw bale walls
>Date: Fri, 06 Jan 2006 20:06:50 +0000
>
>Hello there from cool but getting warmer Canada…
>
>A little while ago I read some information on the subject of convection 
>within straw bale walls and would like to know if this is a resolved issue 
>in Northern Europe ?
>
>Hasit been established with support from testing or evidence of problems 
>that this phenomena exists in the straw bale world ? I am not a scientist 
>so I cannot  reach a conclusion from scientific data myself but I could 
>understand simple terms…8)
>
>I hope this will be possible as there is much debate here on the subject 
>and there has been no testing here as far as I know. The idea that bale 
>walls arein fact likely to rot without there being barriers in between each 
>course is worrying some people!
>
>Thank you all for your consideration
>
>Michael Lough
>
>
>
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