Dear fellow
straw balers,
I appreciate help of all who replied to my previous posts so
far, which have
helped me a lot with planning my first straw bale house. I
have been able to
put together a house plan for post & beam with straw bales
outside and now
when it is finished I would like to ask you for an opinion. I
am attaching wall
intersection and want to hear your say. If you consider that
your replies are
too valuable to share freely, please give me number and I am
willing to pay a
certain amount if it will help me with my planning (reasonable
answers with
theoretical explanation why should it be done so and so)
The questions that are still crossing my mind are:
1. are OSB plates really better than
wooden boards on the inside of the post & beam structure.
Timber guys told
me the wooden boards breathe too much which make the clay
plaster break. I know
wooden boards would be cheaper and more natural but I don`t
really want to have
cracks on my walls. They tell me OSB plates breathe enough. Is
it true? The
same question with the OSB plates on the outside of the
structure: do they
breathe enough or will they make moisture on the straw bales
when warm air will
go from outside to the inside? Or is the lime plaster enough
to suck up all the
moisture from the straw bale? And how much moisture can really
go through the
lime plaster? If it is low, than I guess it shouldn`t be a
problem. What
happens when warm air goes through the wall from the inside to
the outside?
Will it condense?
2. Another question is what percentage
of straw bale can be pressed for every meter? If the straw
bale wall is 10
meters high, how much should it be compressed that it won`t
fall down/compress
any further in the future?
3. as far as I know it is necessary to compress the straw bale
wall, to avoid
settling/compressing in the future which would also make the
lime plaster
crack. How do I compress the walls where I have windows and
doors? Is it better
to use board frames or are boards above the openings
sufficient?
4. I am planning to do floor and roof isolation with straw
bales as well. I can
remember a discussion from Belgium that it is not best to put
straw bales in
the floor, but can`t remember the explanation why not. I think
it was professor
Minke who opposed the straw bale floor isolation but there
wasn`t enough
evidence to prove this theory.
5. I am also a bit concerned about the straw bales on the
roof. We are planning
to do the continuous straw bale layer with only screws in the
middle to fix the
roof laths so there shouldn`t be no problems with the thermal
bridging. The
thing that concerns me is the classical vapor foil which will
be laid above the
straw bales. It is supposed to be breathable, but I am afraid
it will make
condensation in the straw bales. The foil is necessary if the
rain gets under
the roof tiles - so it slips down the foil. Would it be maybe
wise to put
another foil below the straw bales, or would it be better to
put dip the straw
bales in clay before putting them on the roof, so it would
such the moisture
out of them?
I appreciate your knowledge, as there are only a few people in
my country who
know something about straw bale building and they have very
little experience
as there are only a few straw bale houses in Slovenia and they
are all done
with infill design which is suitable for certain regions, but
not for where I
live where we have big temperature differences. If everything
goes right the
house will be standing till the next ESBG, which I plan to
attend. I will start
working with straw bales professionally next year in September
and will
also initiate straw bale association of Slovenia to share the
knowledge of straw
bale building.
With best wishes to you all,
Jure Požar, SLOVENIA STRAWBALE BUILDING
