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Hi Marcus
It depends also of your design (e.g. did you
think about a good roof overhang, and did you imply measures to
prevent moist crawling up from the ground level into the bales and bricks?), the
local weather conditions (heavy showers, strong winds with rains, long periods
of fog etc.?). When your design is good, the masonry work is done well
(without cracks, holes etc.) and your outside lime layer is also being plasterd
without cracks, it should function allright.
But, when you have your doubts in any of these
respects, then your architect has a point, especially when the brick wall is
rather thick.
When water / moist can enter the wall system (and
bricks can absorb huge quantities) because there's a leak somewhere (e.g. caused
by a neglected crack in the lime plaster) than surely a problem can arise.
Because the brick wall is so thick, it 'll take substantial time for
the damp / moisture to disappear out of the wall system
again. When this time period is more than about a week, the rotting
proces could start (also depending of the temperature, the quality of the
bales etc.).
You could think about putting a damp foil in
between the straw bale insulation wall and the brick wall, and also
some space (a couple of cm's) between this foil and the brick wall, and make
about 2 till 4 small ventilation holes in the brick wall of 1 cm diameter
each, every time repeating this at a distance of say every 3 m,
so a bit of wind can enter behind the brick walls (this is more or less the
Dutch way of building with masonry work). This is offcourse only a good
idea, if the brick wall does have no real insulation function.
Succes
Rob Gort
Bouwcarrousel bv
----- Original Message -----
Sent: Wednesday, September 12, 2007 8:53
PM
Subject: [Strawbale] Strawbale and brick
walls
Hi there,
I am helping a friend who is planning a new
two storeyed brick/strawbale house with an earth roof. We have knocked down an
older building on the existing site and have a lot of bricks. What he has in
mind is to use the bricks to build the load bearing part of the structure and
use strawbales for insulation. So the walls will be very thick.
The
query is... that an architect friend said he wouldn't recommend putting
strawbales in contact with the brick wall as moisture will wick from the brick
walls into the straw causing a damp problem. He based his theory on the fact
that wooden beams in Germany are known to be susceptible to rot when they go
through brick walls. I can imagine that with an older house
with
insufficient damp-proofing, moisture can wick up the walls to the
height of the beams and cause a problem BUT... with a new house, with good
damp proofing, I can't see where the moisture would come from.
The
house would have earth plaster on the inside and outside (with a limewash
finish) so there wouldn't be any barrier to stop vapour going through
the walls.
Does anyone have any ideas about this or have heard any
experience of people cladding brick houses with straw.
Any ideas would
be greatly appreciated.
Marcus
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