[Strawbale] strawbale vaults and domes, again
ArchiLogic at yahoo...
Fri Oct 15 20:41:43 CEST 2010
On Tue, 12 Oct 2010 15:45:38 -0400, Derek Roff <derek at unm...> wrote:
> You can see some recent dome and vault ideas from Gernot Minke of
> Germany (building in Slovakia).
Thanks for the link to the Slovakian SB dome project.
I had seen some chatter about the project on the Euro SB List but hadn't
yet seen anything of the actual building.
I noted in one of the comments in the blog (quoted below):
================quoted blog material ==============
piatok, 8. októbra 2010
... the moisture levels in the straw bales has been difficult to
understand. Even after weeks of drying the plaster the moisture level in
the middle of the straw bales increased from 85%RH to 90%RH. The sensors
in the straw bales just below the outside clay plaster has been increasing
with higher outside temperatures and lower with at low temperatures - the
opposite of what I would expect. The average moisture level in these areas
are about 95%RH... of course the weather has not been very kind, here one
of the rainy and windy days, but the clay still seems to be fairly dry.
============ end of quoted blog material ==========
I hadn't had a thorough enough look at the blog to determine when the
above comment/observation was made -- before or after the EPDM membrane
was placed over the exterior of the plastered bales -- but the
(scarily-high!) moisture levels which were increasing
with higher outside temperatures would seem to be exactly what one would
expect as the sun heating up the exterior plaster would result in moisture
from the plaster (covered or uncovered by rubber sheet) being driven into
the straw via the process known as inward vapour drive, same process that
would affect wetted plaster on a "normal" Sb wall.
As with any bale construction on which a vapour-impermeable membrane
prevents transpiration of moisture (whether it be from bulk moisture
transfer (ie leaks) or ambient humidity, the arrangement *appears*
problematic. (I haven't delved deeply enough into the blog to see how the
designers addressed this issue.)
=== * ===
Kanata, Ontario, Canada
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