[GSBN] Failures due to moisture migration in bale walls

Derek Stearns Roff derek at unm.edu
Sat Jun 27 10:59:56 CDT 2015

I’ve not seen failures from moisture migration, but I am responding with a slightly different suggestion.  I’ve read a number of articles on wall and moisture issues, including optimum construction scenarios, by local Ontario hero and GSBN member John Straube, and his colleagues.  Articles on the Building Science Corporation website and Green Building Advisor generally do not advocate a plastic vapor barrier except in cold climates much more severe than the Toronto area.  Are those articles of any use to you, Chris?  This question has been well-researched outside the strawbale world, and the documentation is good, that plastic vapor barriers do more harm than good, until you get up into the truly frozen north.  Even there, they aren’t obligatory, but just one option.


Derek Roff
derek at unm.edu<mailto:derek at unm.edu>

On Jun 27, 2015, at 9:35 AM, Chris Magwood <chris at endeavourcentre.org<mailto:chris at endeavourcentre.org>> wrote:

Hi all,

I'm working on a "defense" of the vapour permeable nature of straw bale walls for a building code for an alternative solutions application here in Ontario.

The building department is particularly concerned about the lack of a vapour barrier in the system (again!). I'm pulling out all the usual test documents and building science theories to help make our case.

But I'm interested in knowing if any of you out there have actually encountered a bale wall that has failed due to moisture migration through the wall, especially during the winter. I've certainly seen some damage done by consistent exposure to rain, or leaky roofs, or other bulk-water intrusions, but I've never seen a moisture migration failure. If that has been the general experience of this list, with its wide variety of climates and building styles, then that would seem to me to make a good evidence-based defense for this.

And if you have seen such a failure, I'd be interested in knowing about the suspected (or known) causes, the conditions that led to this failure, and whether or not the situation was able to be remedied.

I don't need everybody on the list to respond... perhaps only those who've seen examples of this type of failure. If the list is silent on this, I'll take that to mean that this really hasn't shown itself to be a major issue, and will say so in my AS application.

Thanks all!


Chris Magwood
Director, Endeavour Centre

Gsbn mailing list
Gsbn at sustainablesources.com

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