Re: [Strawbale] Convection in SB walls

[carolatkn@aol...]

Hi all
Good dense bales with nicely straightened ends, compressed in a wall (load bearing or framed) with all gaps well stuffed with straw (or straw with a little clay slip rubbed in) at the (direct in to the bales) wet plastering stage will suffer very little heat loss from convection. One of the great advantages of a straw bale wall is that you can see/check the integrity of your insulation before you go any further - by comparison to insulation blown into a cavity or batts that can be poorly fitted or slump after fitting. 
I particularly like this quote that I found when writing up my thesis -

 

(Little, 2005 page 51)

âJan Lecompteâs 1990 paper âThe influence of natural convection on the thermal quality of insulated cavity constructionâ makes clear the substantial effect that air passage through these gaps has on the thermal performance of insulated cavity wallsâââ..Lecompte measured a 193% increase in heat transfer due to a 10mm voidâââââââ.even a 5mm void could lead to a 35% increase in heat transferâ

Enjoying the discussion
all the best

Carol

www.homegrownhome.co.uk

-----Original Message-----
From: Dave Howorth <dave@howorth....uk>
To: European strawbale building discussions <strawbale@amper....muni.cz>
Sent: Wed, 8 Dec 2010 21:43
Subject: Re: [Strawbale] Convection in SB walls

On Wed, 2010-12-08 at 21:58 +0100, forum@lamaisonenpaille... wrote:
> the convection that is common in fibrous insulation materials.

I've wondered what can be done about this. Convection needs height to
really get going so I wonder if some less permeable layer laid
horizontally between the layers of bales might reduce it some.

Obviously you don't want it totally impermeable to water vapour or
liquid, and you want it cheap. So for a completely off the wall idea,
how does laying sheets of old newspaper on top of each row of bales
sound? They'll get holed a bit but that shouldn't matter too much.

Cheers, Dave

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