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GSBN:Re:Moisture Problem:: dynamic moisture transport simulation



Rene,
I'll try to contribute a little to the moisture discussion by giving a short
summary to our acitivities in this field. Sorry for not corresponding
directly to the earlier messages.

In the last months we did some straw bale- 'dynamic moisture transport
simulation' with WUFI. You'll find some english description about WUFI at
<a  target="_blank" href="http://www.wufi.de/index_e.html";>http://www.wufi.de/index_e.html</a>. But I guess you know this software. It
seems to be one of the worldwide standards systems for this task.

The 'Fraunhofer Institut Bauphysik' did the straw bale simulations. They
also did a lot of publications to hygrothermal behaviour of walls. You'll
find them on their (english) website:
<a  target="_blank" href="http://www.hoki.ibp.fhg.de/ibp/publikationen/publikationen_e.html";>http://www.hoki.ibp.fhg.de/ibp/publikationen/publikationen_e.html</a>. Take a
closer look to the dissertation of Sedlbaur.

The report about two strawbale walls we assigned gives the following
results:

1. In german standard climate (Holzkirchen) unprotected straw bales (but
under roof) molds(!).
This is merry nonsense, but it shows, that this dynamic simulation software
calculates to surely for our straw bales.
2. As expected after the first point above, our straw bale wall with 3cm
wheat stabilized clayplaster, 45cm straw, 3cm interiour clay plaster, molds
at about 6000 hours in the year. In reality the wheat stabilized clayplaster
works wunderful, for example at www.fasba.de >> projekte  >> Strohpolis.
3. An alternative wall construction, which we don't prefer,
behind-ventilated timber cladding, 2cm wood soft fiber, 35cm straw, 1,5cm
OSB interiour doesn't mold.

Now we've at least one configuration which works under dynamic simulation
done by computer. The reality is fortunately more friendly to our bales. In
the next months, we've to find a way to proove the clayplaster option.

To the moisture problem of Paul Lacinski's client:
I had a moisture problem with a lime layered clayplaster in this summer too.
We had to renew the weathersided (western) wall of the straw bale house.
You'll find it on www.fasba.de >> projekte  >> Schier.

We assume, that the 'resistance against vapor' (accurate expression?) of the
lime layer was too high, but let too much driving rain coming in.
I had not enough endurance to read all the partly very long messages from
the moisture thread, but I guess the problem Paul Lacinski's client had is
not similar to our's above.

We took at a time 10 straw samples from 5 buildings and analyzed their
content of fungus. Two samples showed (amongst others the weatherside of
House Schier) much above common house dust concentration of fungus.

Puh, several month since I had to write english...

(On Thursday the german licensing authority decides about our request for a
general german approval of straw bales as infill insulation, our main
challenge was to prove, that straw bales don't mold)


Dirk Scharmer
www.fasba.de

-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Rene Dalmeijer
Sent: Thursday, November 10, 2005 9:43 PM
To: GSBN
Subject: Re: GSBN:Moisture Problem

Paul,

Thanks very much for your frank and open report on the McSweeney house.
I see some parallels to house I have just help complete. Since
plastering the exterior with a hydraulic plaster I have monitored the
moisture level. Specifically because we noticed a damp spot on the
exterior on the spot most exposed to weather that only went away slowly
after removing the scaffolding. The spot dried in about 2 weeks it is
not visible anymore. After doing some hard thinking I realized it was
caused  by splash from water dripping from a roof drain on the scaffold
hitting the wall where the wet spot was only noticed after the scaffold
was removed.

Now back to the parallel with the McSweeney house. The wet spot
prompted me to regularly monitor the bales around the house. We only
just plastered a few of the interior walls with earth plaster so most
places were and are easily accessible from the inside. Instead of the
moisture levels dropping, what I expected, They have been rising not
much but up from 14% to 16% and only on the very outside 30-50mm. The
wet spot is slowly drying albeit very slowly. The house is not occupied
yet and is well ventilated.

Your mail has warned me though to keep a careful watch on the house. As
I subscribe to your idea that the Scandinavian model of having less
permeable finishes on the inside and more open finishes on the exterior
is good practice in the Dutch type of climate. I would love to do a
dynamic moisture transport simulation to better understand what is
happening. Sven Eweleit of Andersehen might be able to help.


Rene
On Nov 10, 2005, at 17:19, Paul Lacinski wrote:

> At the end of this email there will also be some questions- I
> hope you all will have some ideas to share.

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