[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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



Hi all!
Great to see Dirk doing analysis and moving this forward. I am not sure what
you mean by WUFI "predicts mold" though, and this could be important.

I have run thousands of different WUFI simulations  on hundreds of different
walls, including strawbale walls, which we correlated to field performance
at the Ridge winery building. It is quite accurate for predicting the
temperature and moisture conditions for strawbale walls if you get the input
data correct, however, IT DOES NOT PREDICT MOLD GROWTH.  I emphasize this
because WUFI is widely used and people often apply WUFI-Bio (a separate
program) or simple 80%RH thresholds to assessing mold growth. We have never
been able to get correlation from field or lab measurements of wood and
paper RH and temperature and mold growth.  Almost all rules are VERY
conservative

The interpretation of mold growth thresholds is, I believe, what explains
Dirk's successful field results .


Dr John Straube
Associate Professor
Dept of Civil Engineering & School of Architecture
University of Waterloo
Waterloo, Ont. Canada
<a  target="_blank" href="http://www.civil.uwaterloo.ca/beg";>http://www.civil.uwaterloo.ca/beg</a>


-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Dirk Scharmer-
FSB
Sent: Tuesday, November 15, 2005 11:22 AM
To: 'GSBN'
Subject: 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.

----
GSBN is an invitation-only forum of key individuals and representatives of
regional straw construction organizations. The costs of operating this list
are underwritten by The Last Straw Journal in exchange for use of the GSBN
as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send
email to GSBN@...HELP in the SUBJECT line.
----

----
GSBN is an invitation-only forum of key individuals and representatives of
regional straw construction organizations. The costs of operating this list
are underwritten by The Last Straw Journal in exchange for use of the GSBN
as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send
email to GSBN@...HELP in the SUBJECT line.
----