[Strawbale] Convection in SB walls

carolatkn at aol... carolatkn at aol...
Wed Dec 8 23:02:40 CET 2010

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)
“Jan Lecompte’s 1990 paper “The influence of natural convection on the thermal quality of insulated cavity construction” makes clear the substantial effect that air passage through these gaps has on the thermal performance of insulated cavity walls………..Lecompte measured a 193% increase in heat transfer due to a 10mm void………………….even a 5mm void could lead to a 35% increase in heat transfer”

Enjoying the discussion
all the best

-----Original Message-----
From: Dave Howorth <dave at howorth....uk>
To: European strawbale building discussions <strawbale at 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 at lamaisonenpaille... wrote:
 the convection that is common in fibrous insulation materials.
I've wondered what can be done about this. Convection needs height to
eally get going so I wonder if some less permeable layer laid
orizontally between the layers of bales might reduce it some.
Obviously you don't want it totally impermeable to water vapour or
iquid, and you want it cheap. So for a completely off the wall idea,
ow does laying sheets of old newspaper on top of each row of bales
ound? They'll get holed a bit but that shouldn't matter too much.
Cheers, Dave
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