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GSBN: Digest for 11/11/04



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-> Re: GSBN:Re: Danny Buck's moisture NM
     by Chris Magwood TLSEditor@...
-> Re:  Re: GSBN:Re: Danny Buck's moisture NM
     by Strawnet@...
-> Re: Danny Buck's moisture NM
     by Derek Roff derek@...
-> RE: GSBN:Re: Danny Buck's moisture NM
     by jfstraube@...
-> Re: GSBN:Re: Danny Buck's moisture NM
     by John Glassford huffnpuff@...


----------------------------------------------------------------------

Date: 11 Nov 2004 14:45:28 -0600
From: Chris Magwood TLSEditor@...
Subject: Re: GSBN:Re: Danny Buck's moisture NM

>My feelings these days are that under no circumstance should we allow
>moisture to enter a straw bale wall in any form from the inside or the
>outside.  Why take a chance on the moisture finding it's way out of a
>wall?  Therefore I am of the opinion that we should make sure that
>moisture in vapour or solid form cannot get into a bale wall.  Therefore
>we should treat the finished coat of render accordingly and use methods
>and materials that will give a water proof wall from BOTH sides.

I think John raises an interesting issue here. I've always stuck by
the breathable argument, and have seen some surprising examples of
drying taking place this way after significant soakings. But I, like
John, don't want to leave it to this process entirely.

I have lately been experimenting with silicate paints (from Eco-House
in New Brunswick). They claim an excellent water repellancy (is that
a word?) and little effect on breathability. I can attest to the
repellant qualities... even on earthen plasters water will bead and
roll off. But does anybody know for sure if the breathability is as
good as is claimed? If so, I think the silicate paints are something
that could be widely promoted for straw bale. They seem to be
relatively non-toxic (again, based on manufacturer claims) and
created with natural materials, the colours are excellent, the cost
is reasonable... Seems like it could be an excellent solution to one
of our biggest concerns, and an easy one too, if it works like it
seems to work.

Chris
- --


***************************

Chris Magwood / Camel's Back Straw Bale Construction
<a  target="_blank" href="http://www.strawhomes.ca";>http://www.strawhomes.ca</a>

Interested in bale building? Have you subscribed to
The Last Straw Journal?
You should!
  <a  target="_blank" href="http://www.thelaststraw.org";>http://www.thelaststraw.org</a>


----------------------------------------------------------------------

Date: 11 Nov 2004 18:32:14 -0600
From: Strawnet@...
Subject: Re:  Re: GSBN:Re: Danny Buck's moisture NM

Hello from Portland - a wetter place than my customary climate (Tucson),
where I am attending the USGBC Greenbuild conference.

I just need to reiterate a point I've made many times on this subject -
that is the impossibility of keeping moisture out of these assemblies. If
we can't keep moisture from getting into double glazed windows - two
pieces of glass separated and sealed with the highest tech materials we
can invent, built in a factory and put into a frame - why would you think
we could build an assembly in the field, with the variability of
materails, designs, workmanship and all that happens to those assemblies
over time and water won't get in? It will. Take that as your base
assumption and make sure it can get out. I can't say this strongly enough
- - things get wet, make sure that the drying capacity is stronger overall
than the wetting mechanisms...

Gotta go...

David

>From:  TLSEditor@...(Chris Magwood)
>Sender:    GSBN@...(GSBN)
>Reply-to:  GSBN@...(GSBN)
>To:    GSBN@...(GSBN)
>>My feelings these days are that under no circumstance should we allow
>>moisture to enter a straw bale wall in any form from the inside or the
>>outside.  Why take a chance on the moisture finding it's way out of a
>>wall?  Therefore I am of the opinion that we should make sure that
>>moisture in vapour or solid form cannot get into a bale wall.  Therefore
>>we should treat the finished coat of render accordingly and use methods
>>and materials that will give a water proof wall from BOTH sides.
>
>I think John raises an interesting issue here. I've always stuck by
>the breathable argument, and have seen some surprising examples of
>drying taking place this way after significant soakings. But I, like
>John, don't want to leave it to this process entirely.
>
>I have lately been experimenting with silicate paints (from Eco-House
>in New Brunswick). They claim an excellent water repellancy (is that
>a word?) and little effect on breathability. I can attest to the
>repellant qualities... even on earthen plasters water will bead and
>roll off. But does anybody know for sure if the breathability is as
>good as is claimed? If so, I think the silicate paints are something
>that could be widely promoted for straw bale. They seem to be
>relatively non-toxic (again, based on manufacturer claims) and
>created with natural materials, the colours are excellent, the cost
>is reasonable... Seems like it could be an excellent solution to one
>of our biggest concerns, and an easy one too, if it works like it
>seems to work.
>
>Chris


David Eisenberg, Director

Development Center for Appropriate Technology
P.O. Box 27513, Tucson, AZ  85726-7513
(520) 624-6628 voice / (520) 798-3701 fax
strawnet@...
<a  target="_blank" href="http://www.dcat.net";>http://www.dcat.net</a>

The Development Center for Appropriate Technology is a 501(c)(3)
non-profit organization. Our primary support comes from charitable
contributions from individuals and businesses, from our educational and
training programs and consulting services, and to a lesser degree today
from foundation grants. Please consider helping support our vital work.
Our mission is to enhance the health of the planet and our communities by
promoting a shift to sustainable construction and development practices
through leadership, strategic relationships, and education. To learn
about DCAT's work and how you can support it, please visit our website at
www.dcat.net



----------------------------------------------------------------------

Date: 11 Nov 2004 21:12:47 -0600
From: Derek Roff derek@...
Subject: Re: Danny Buck's moisture NM

I agree with David.  It seems to be a common dream of builders and
designers to keep all water out, for ever.  I suppose that we have a dream
of building perfect houses.  Perfection might not be bad target, but it's
impossible to attain.  The problem comes when designing for perfection
decreases quality, rather than increasing it.  That has happened many times
on many buildings, when people believe they can keep all the water out.
These houses are the most likely to suffer catastrophic failures.  Examples
include the many centuries-old adobe structures, which were re-roofed and
plastered in modern materials, in order to "protect" them.  A few were
destroyed, and most suffered severe damage over the course of a mere ten or
twenty years, before the new materials were removed.

Ahhh, but that was twenty years ago.  Now we know better, and have better
materials.  We are really going to protect those buildings now...

This relates directly to Danny's project.  I suggest that there are many
advantages to leaving the interior mud plaster as is.  I think that sealing
the plaster would do more harm than good.  I doubt the theoretical
supposition, which Danny quoted, that the interior plaster should be less
permeable than the exterior plaster.  Neither laboratory research nor field
monitoring support that approach.  Rather, my reading of the research tells
me that having good permeability in all plasters is the safest course for
strawbale walls.  Research by the Canada Mortgage and Housing Corporation
indicates that even in Arctic conditions, the amount of moisture diffusing
through a continuous air barrier, from the living space into a wall, is
small.  On the other hand, the amount of moisture moving with air through
small flaws and holes in the air barrier can be very large and have severe
consequences.  While we should be vigilant in reducing these holes and
flaws, as David points out, it is hubris to suppose we can attain
perfection in this regard.  Therefore, we need the broad expanses of
permeable plasters to ameliorate the effects of the inevitable moisture
infiltration.

If it were my house, I would not seal or modify the mud plaster.  I think
it is a big plus for moisture handling.  Removing the elastomeric from the
outside would also be an advantage, in my opinion.  I wish I knew a simple
way to do it.  John Straube's testing indicates that vapor permeable, water
repelling coatings, such as siloxane, can be quite effective over permeable
exterior plasters.  John Swearingen has reported using this material with
success and satisfaction in California.  I don't know if the silicate
paints that Chris refers to offer similar advantages.  Independent testing
is needed.

Derek

- --On Thursday, November 11, 2004 7:11 PM -0500 Strawnet@...:

> Hello from Portland - a wetter place than my customary climate (Tucson),
> where I am attending the USGBC Greenbuild conference.
>
> I just need to reiterate a point I've made many times on this subject -
> that is the impossibility of keeping moisture out of these assemblies. If
> we can't keep moisture from getting into double glazed windows - two
> pieces of glass separated and sealed with the highest tech materials we
> can invent, built in a factory and put into a frame - why would you think
> we could build an assembly in the field, with the variability of
> materails, designs, workmanship and all that happens to those assemblies
> over time and water won't get in? It will. Take that as your base
> assumption and make sure it can get out. I can't say this strongly enough
> - things get wet, make sure that the drying capacity is stronger overall
> than the wetting mechanisms...
>
> Gotta go...
>
> David



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...



----------------------------------------------------------------------

Date: 11 Nov 2004 21:50:29 -0600
From: jfstraube@...
Subject: RE: GSBN:Re: Danny Buck's moisture NM

Water will get in.  Try to reduce it as muich as sensible, and balance
it with as much drying as you and the climate can provide.  This is the
same set of rules for all buildings.  Sealing the bales is sheer
madness, in therory and in practise.
I have reviewed the test data from the EcoHouse silicate paints and they
are truly amazing -- water repellent, vaor permeable, highly durable.
We should be trying them in the field more often, since the lab tests
are unequivocal that they work.
In New Mexico it makes little sense to worry much about rleative vapor
permeance.  Control rain firsts, then air, and vapor will ake care of
itself.

John Straube
School of Architecture and Dept of Civil Engineering
University of Waterloo
Waterloo, 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 Derek Roff
Sent: November 11, 2004 21:54
To: GSBN
Subject: GSBN:Re: Danny Buck's moisture NM


I agree with David.  It seems to be a common dream of builders and
designers to keep all water out, for ever.  I suppose that we have a
dream of building perfect houses.  Perfection might not be bad target,
but it's impossible to attain.  The problem comes when designing for
perfection decreases quality, rather than increasing it.  That has
happened many times on many buildings, when people believe they can keep
all the water out. These houses are the most likely to suffer
catastrophic failures.  Examples include the many centuries-old adobe
structures, which were re-roofed and plastered in modern materials, in
order to "protect" them.  A few were destroyed, and most suffered severe
damage over the course of a mere ten or twenty years, before the new
materials were removed.

Ahhh, but that was twenty years ago.  Now we know better, and have
better materials.  We are really going to protect those buildings now...

This relates directly to Danny's project.  I suggest that there are many
advantages to leaving the interior mud plaster as is.  I think that
sealing the plaster would do more harm than good.  I doubt the
theoretical supposition, which Danny quoted, that the interior plaster
should be less permeable than the exterior plaster.  Neither laboratory
research nor field monitoring support that approach.  Rather, my reading
of the research tells me that having good permeability in all plasters
is the safest course for strawbale walls.  Research by the Canada
Mortgage and Housing Corporation indicates that even in Arctic
conditions, the amount of moisture diffusing through a continuous air
barrier, from the living space into a wall, is small.  On the other
hand, the amount of moisture moving with air through small flaws and
holes in the air barrier can be very large and have severe consequences.
While we should be vigilant in reducing these holes and flaws, as David
points out, it is hubris to suppose we can attain perfection in this
regard.  Therefore, we need the broad expanses of permeable plasters to
ameliorate the effects of the inevitable moisture infiltration.

If it were my house, I would not seal or modify the mud plaster.  I
think it is a big plus for moisture handling.  Removing the elastomeric
from the outside would also be an advantage, in my opinion.  I wish I
knew a simple way to do it.  John Straube's testing indicates that vapor
permeable, water repelling coatings, such as siloxane, can be quite
effective over permeable exterior plasters.  John Swearingen has
reported using this material with success and satisfaction in
California.  I don't know if the silicate paints that Chris refers to
offer similar advantages.  Independent testing is needed.

Derek

- --On Thursday, November 11, 2004 7:11 PM -0500 Strawnet@...:

> Hello from Portland - a wetter place than my customary climate
> (Tucson), where I am attending the USGBC Greenbuild conference.
>
> I just need to reiterate a point I've made many times on this subject
> - that is the impossibility of keeping moisture out of these
> assemblies. If we can't keep moisture from getting into double glazed
> windows - two pieces of glass separated and sealed with the highest
> tech materials we can invent, built in a factory and put into a frame
> - why would you think we could build an assembly in the field, with
> the variability of materails, designs, workmanship and all that
> happens to those assemblies over time and water won't get in? It will.

> Take that as your base assumption and make sure it can get out. I
> can't say this strongly enough
> - things get wet, make sure that the drying capacity is stronger
overall
> than the wetting mechanisms...
>
> Gotta go...
>
> David



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...

- ----
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of regional straw construction organizations. The costs of operating
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----------------------------------------------------------------------

Date: 11 Nov 2004 22:11:37 -0600
From: John Glassford huffnpuff@...
Subject: Re: GSBN:Re: Danny Buck's moisture NM

G 'day DEsert Dave

See you are busy as always.

We need to be careful with moisture mate very careful.

Strawnet@...:

>Hello from Portland - a wetter place than my customary climate (Tucson),
>where I am attending the USGBC Greenbuild conference.
>
>I just need to reiterate a point I've made many times on this subject -
>that is the impossibility of keeping moisture out of these assemblies. If
>
My experience is now showing that we must avoid moisture in any form
getting into bale walls.  No matter how good our detailing is when
moisture gets in it is very very hard for it to get out of a straw bale
wall without doing considerable damage on the way out that is, if it
gets to get out in the first place.

Straw will absorb a heck of a lot of moisture before it starts to travel
down and out through the bottom plates.  Even then I have seen very few
bottom plates that have weep holes to allow moisture out.  What happens
on the way out is that the straw will suck the moisture in to saturation
point and unless there is a drying mechanism in the walls somehow, then
the straw gets wetter and wetter and eventually starts to break down.
 This can happen in a matter of days not weeks.

I think we have two areas here that are being discussed one is vapour
permeance and one is liquid water.  To say a wall can breathe is
incorrect to say that it can exchange water vapour is probably correct
but at what stage does water vapour turn into liquid water?  Do we want
to take the risk of this happenning?

Once the break down has started then it is too late as either the straw
will go mouldy or turn into a very wet black compost.  I speak from
experience.  So what to do?

1.  Do not build in straw bale in high humid, high rainfall areas such
as the tropics.
2.  Waterproof any straw bale walls in high humid areas of the house
such as a bathroom.
3.  Build verandahs all round and keep all moisture off the walls in the
first place.
4.  Make sure that the house has good venting to get rid of high
humidity mechanically before it gets to the walls.
5.  Use a render mix that can handle moisture such as a lime earthen mix
or use an elastomeric paint that allows exchange of vapour.

I do not know the answer to this one but my experience again is showing
that the lime/earth/chaff mix is working well under all sorts of
conditions down under.  Even when the moisture turned into liquid water
in great volumes in one house the render mix showed where the trouble
was because the grain in the chaff sprouted and pushed the finish lime
render mix off the wall!!!

PS
John Starube wrote;

Water will get in.  Try to reduce it as muich as sensible, and balance
it with as much drying as you and the climate can provide.  This is the
same set of rules for all buildings.  Sealing the bales is sheer
madness, in therory and in practise.
I have reviewed the test data from the EcoHouse silicate paints and they
are truly amazing -- water repellent, vaor permeable, highly durable.
We should be trying them in the field more often, since the lab tests
are unequivocal that they work.
In New Mexico it makes little sense to worry much about rleative vapor
permeance.  Control rain firsts, then air, and vapor will ake care of
itself.

John Straube
School of Architecture and Dept of Civil Engineeri

John I am not sure if I understand waht you are saying here?  Do you
mean to that sealing the blaes is not a good idea by using a silcone
based paint?  or by other methods? I like the use of silocone paints or
elastomeric paints such as Murobond.  If we had not used Murobond on one
of our early buildings it would not be around today in effect it sealed
the building but I suppose not 100% water proof as they said that the
product allowed vapour permenace.

We need more testing for moisture problems the last frontier for straw
bale.  Especailly for old straw wolf builder type chaps.

Kind regards The Straw Wolf.




----------------------------------------------------------------------

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