[GSBN] Maximum Density for straw insulation
sabale at bigpond.com
Tue Oct 4 16:30:28 CDT 2016
My experience when people are talking about very dense bales it “export Bales” they are talking about.
These are highly compressed some ending up as small as 450mm x 350mm x 200mm with a weight of 12kg.
Giving a total m3 weight of around 380kg. and strapped with steel or polly straps.
These bales will perform more like timber , perhaps a lower R value.
But due to their weight will have increased mass as well as thermal mass.
As 3 or more standard small square bales are compressed into the space of one,
They become a 2 person lift, along with the additional overall Wall weight this has an impact on footing design.
Garden mulch bales less than 100 kg / m3 may well have a reduced R value , along with other issued if used in construction.
Construction grade bales around the 115 /120 kg per m3 will achieve great performance , as shown by any existing R value testing.
Export grade bales of over 350 ( even 200 kg ) per m3 may not ( I suggest will not) show any increased R value , but only add to construction costs.
While the abo does not add any information about testing the idea, to me it does add to the greater discussion of
R5-6 as a standard ( construction grade) bale produced on farm, as to making more work / inputs into product ( bales ) for perceived minor gain.
Regards Lance Kairl
House of Bales
From: Gsbn [mailto:gsbn-bounces at sustainablesources.com] On Behalf Of John Swearingen
Sent: Wednesday, 5 October 2016 6:17 AM
To: Global Straw Building Network <gsbn at sustainablesources.com>
Subject: Re: [GSBN] Maximum Density for straw insulation
I would agree...I've never seen evidence of crushed straw in our industrial-strength 3-string bales. Softer bales would allow more air-exchange and convection, reducing the effectiveness as insulation--but I think the differences will be small.
John "I might be dense, but I'm still soft" Swearingen
On Tue, Oct 4, 2016 at 4:41 AM Rene Dalmeijer <rene.dalmeijer at hetnet.nl <mailto:rene.dalmeijer at hetnet.nl> > wrote:
I see nobody is reacting to your mail. I have not been doing any testing myself but as far as I have been able to determine on the tests I have seen, it is almost impossible to compress strawbales sufficiently to decrease the effective insulation value. One of the reasons for this is that in thicker samples some convection takes place in the cavity with open cell insulation like straw bales. This means in many cases increasing the density improves the effective insulation value to some extent. As far as I am aware how much variation has not been determined conclusively as there are too many variables influencing insulation values for hole wall systems. What I dare to venture to say this variation is not significant given a building grade 115kg/m3 straw bale giving an R Value of 5-6 (metric, 28-34 imperial) for the finished wall. (but as you know this is debatable)
Snug in some warm bales (R 5-6) in the reclaimed swamp at the mouth of the Rhine
On Sep 13, 2016, at 12:10, Rikki Nitzkin wrote:
> Hi everyone,
> Recently returned from our national gathering, I have a question about thermal transmission testing….
> There was a debate going on at our event about what is the “best” density for a bale, referring to insulation (not structural) is.
> Some people were under the impression that “the denser the better” and others that an “overly” dense bale will insulate less, as the fibers of straw would be crushed and retain less air - therefore insulating less.
> Has anyone tested this? Is there data anywhere on what the Maximum or Minimum Density would be for best insulation?
> thanks, Rikki
> Rikki Nitzkin
> Strawbale Building and Clay Plaster:
> education, consulting, and building
> www.rikkinitzkin.worpress.com <http://www.rikkinitzkin.worpress.com>
> tallerconco at gmail.com <mailto:tallerconco at gmail.com>
> (+ 34) 657 335 162
> (+ 34) 974 032 950
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> Gsbn at sustainablesources.com <mailto:Gsbn at sustainablesources.com>
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