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GSBN: Digest for 12/12/07



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


-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by jeff@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by jswearingen@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by David Eisenberg strawnet@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by jswearingen@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by Laura Bartels laura@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by Graeme North ecodesign@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by David Eisenberg strawnet@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by jswearingen@...
-> Fwd: Re: [nbne] Fwd: Re: Pea Gravel
     by Mark Piepkorn mark@...
-> Re: GSBN:Fwd: Re: [nbne] Fwd: Re: Pea Gravel
     by David Eisenberg strawnet@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by Chris Magwood cmagwood@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by Tom Hahn tomhahn@...
-> Re: GSBN:Fwd: CASBA_ Pea Gravel
     by Martin Hammer mfhammer@...


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

Date: 11 Dec 2007 23:49:57 -0500
From: jeff@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

David and Anni (or Catherine et al),

I completely agree with your questioning of this requirement. In our dry
environment, we use all sorts of materials between the sills, with fine
results.

IMHO, this brings up the ever-present issues related to what we codify.
Any mention of specific materials makes things like this prescriptive,
not open to performance qualifications, nor the ability to prove intent,
since no accompanying explanation of intent is present. Any future
attempts to codify bale construction techniques should have accompanying
intentions. There are too many environments and situations that will
arise conflicting with any codification of our work.

The recent work by Martin Hammer and everyone else in the past has been
wonderful, but I really think we can do better and qualify our intent,
just as other parts of the code include. There are accompanying text of
intent for code structures in Canada (B.C.) and whole sections of the
I.B.C. that have intent documents.

Anything we do with regards to codes will serve us better by including
our intentions so those of us in questionable circumstances can benefit
from any contributing work in these areas.

Jeff





Catherine Wanek wrote:
> I am forwarding this inquiry from the California Straw Building
> Association (CASBA) list from award-winning architects David Arkin &
> Anni Tilt. Perhaps this will stimulate discussion on the GSBN e-waves.
> -Cat
>
>
>> From: "David Arkin, AIA" david@...
>> Date: Tue, 11 Dec 2007 17:21:39 -0800
>> Subject: CASBA_Mem Pea Gravel
>> Fellow CASBAnauts (CASBAnuts?):
>>
>> We haven't used pea gravel between our sill plates for some time now,
>> using rigid insulation instead. My opinion is that if a bale wall has
>> enough water in it to need 'drainage' (from any source), those bales
>> are goners.
>>
>> The building official in Sonoma is citing it's recommendation in
>> SB332 as a good enough reason to require that it be there. SB332
>> says, "There shall also be a drainage plane between the straw and the
>> top of the foundation, such as a one inch layer of pea gravel." Does
>> anyone know of the intent of this?
>>
>> More importantly, does anyone know of any testing as to why this
>> might (or might not) be a good idea?
>>
>> Your thoughts (and/or Holiday Greetings) always appreciated,
>>
>> David and Anni
>>
>> * * * * *
>> Arkin Tilt Architects
>> Ecological Planning & Design
>>
>> David Arkin, AIA, Architect
>> LEED Accredited Professional
>> CA #C22459/NV #5030
>>
>> 1101 8th St. #180, Berkeley, CA 94710
>> 510/528-9830
>> www.arkintilt.com
>>
>> "There is no way to peace. Peace is the way."
>> o A. J. Muste
>>
>>
>>
>> -
>> Use REPLY to respond to the sender only or
>> use REPLY ALL to respond to the entire list.
>> CASBA Website can be found at <a  target="_blank" href="http://www.strawbuilding.org";>http://www.strawbuilding.org</a>
>
> ----
> For instructions on joining, leaving, or otherwise using the GSBN
> list, send email to GSBN@...HELP in the
> SUBJECT line. ----
>
>


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

Date: 12 Dec 2007 10:23:19 -0500
From: jswearingen@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

We've supported the use of pea-gravel or some other broken plane, not
because we think the wall will be drenched with water, but based on our
observation of vapor migration and accumulation through bales.  Here's our
reasoning:

   - Vapor is continually moving around inside a bale wall as temperature
   conditions change. Many observations have been made of considerable diurnal
   movement of moisture within a bale wall, and significant differentials in
   humidity between the top and bottoms of a wall.
   - It's easily observed that as moisture migrates through a bale it is
   prone to stop and accumulate at any impermeable surface, and reach a
   concentration where rotting will occur. This is why we avoid vapor barriers
   on the bale sides. The same conditions can occur at the tops and bottoms of
   a wall.
   - Bear in mind, also that the sills are at the bottom of the wall
   where the most wetting occurs from direct rain and rain splash from the
   ground.  Some of this moisture will initially migrate to the bottom of the
   wall by gravity, especially in conditions of cold rain.  As David Arkin is
   wont to say, good boots, good hat, etc.
   - Some moisture may come from the footings: even though there might be
   some vapor barrier in place, it is often imperfect due to foundation design
   and execution.
   - Leaks do occur  around windows and cracks, and gravel does provide a
   path for dissipating moisture.
   - Accumulated rot in one place, the bottom of the bales, could
   compromise the integrity of the wall.

I understand that many of us are very, ah, fixated, on R-values and
buttoning up our coats.  I would not trade increased insulation for
cautious vapor management. We typically use two 4x plates of wood, which is
good for at least R-10---slightly low but not so far from optimal for
horizontal insulation when located low in the building shell, in our
climate.  We have also used, in colder climates, a scheme we learned from
Ken and Polly, simply alternating strips of rigid insulation with channels
of pea gravel, so you can get another 4-5" of rigid down there and make Al
Gore a little happier...

John "Gore-Techs" Swearingen



On Dec 11, 2007 9:37 PM, Jeff Ruppert jeff@... wrote:

> David and Anni (or Catherine et al),
>
> I completely agree with your questioning of this requirement. In our dry
> environment, we use all sorts of materials between the sills, with fine
> results.
>
> IMHO, this brings up the ever-present issues related to what we codify.
> Any mention of specific materials makes things like this prescriptive,
> not open to performance qualifications, nor the ability to prove intent,
> since no accompanying explanation of intent is present. Any future
> attempts to codify bale construction techniques should have accompanying
> intentions. There are too many environments and situations that will
> arise conflicting with any codification of our work.
>
> The recent work by Martin Hammer and everyone else in the past has been
> wonderful, but I really think we can do better and qualify our intent,
> just as other parts of the code include. There are accompanying text of
> intent for code structures in Canada (B.C.) and whole sections of the
> I.B.C. that have intent documents.
>
> Anything we do with regards to codes will serve us better by including
> our intentions so those of us in questionable circumstances can benefit
> from any contributing work in these areas.
>
> Jeff
>
>
>
>
>
> Catherine Wanek wrote:
> > I am forwarding this inquiry from the California Straw Building
> > Association (CASBA) list from award-winning architects David Arkin &amp;
> > Anni Tilt. Perhaps this will stimulate discussion on the GSBN e-waves.
> > -Cat
> >
> >
> >> From: "David Arkin, AIA" david@...
> >> Date: Tue, 11 Dec 2007 17:21:39 -0800
> >> Subject: CASBA_Mem Pea Gravel
> >> Fellow CASBAnauts (CASBAnuts?):
> >>
> >> We haven't used pea gravel between our sill plates for some time now,
> >> using rigid insulation instead. My opinion is that if a bale wall has
> >> enough water in it to need 'drainage' (from any source), those bales
> >> are goners.
> >>
> >> The building official in Sonoma is citing it's recommendation in
> >> SB332 as a good enough reason to require that it be there. SB332
> >> says, "There shall also be a drainage plane between the straw and the
> >> top of the foundation, such as a one inch layer of pea gravel." Does
> >> anyone know of the intent of this?
> >>
> >> More importantly, does anyone know of any testing as to why this
> >> might (or might not) be a good idea?
> >>
> >> Your thoughts (and/or Holiday Greetings) always appreciated,
> >>
> >> David and Anni
> >>
> >> * * * * *
> >> Arkin Tilt Architects
> >> Ecological Planning &amp; Design
> >>
> >> David Arkin, AIA, Architect
> >> LEED Accredited Professional
> >> CA #C22459/NV #5030
> >>
> >> 1101 8th St. #180, Berkeley, CA 94710
> >> 510/528-9830
> >> www.arkintilt.com
> >>
> >> "There is no way to peace. Peace is the way."
> >> =97 A. J. Muste
> >>
> >>
> >>
> >> -
> >> Use REPLY to respond to the sender only or
> >> use REPLY ALL to respond to the entire list.
> >> CASBA Website can be found at <a  target="_blank" href="http://www.strawbuilding.org";>http://www.strawbuilding.org</a>
> >
> > ----
> > For instructions on joining, leaving, or otherwise using the GSBN
> > list, send email to GSBN@...HELP in the
> > SUBJECT line. ----
> >
> >

>
>


- -- 
John Swearingen
Skillful Means, Inc.
Design and Construction
www.skillful-means.com


- --- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
- ---


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

Date: 12 Dec 2007 13:11:19 -0500
From: David Eisenberg strawnet@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

Hi all,

There are several excellent points already made here:

- - that prescriptive requirements, whatever they might be, are typically 
limiting and not always appropriate, especially in the hands of 
designers or code officials with limited understanding of particular 
systems, materials or methods of construction,

- - that in this case, we actually don't have research and testing 
results to rely on for this,

- - that there are a number of competing concerns wanting to be addressed 
and probably an even greater number of theories and strategies 
competing to meet them,

- - that including intent is critically important in writing codes, 
though missing more often than not in most codes (this should not be a 
deterrent to us getting it right going forward),

- - that there are at least a couple of methods (with some variations) 
that predominate now - pea gravel or something equivalent and rigid 
foam insulation,

- - and of course, there is the first point, that David Arkin and company 
have a particular problem at present and have asked for some help...

The language "There shall also be a drainage plane between the straw 
and the top of the foundation, such as a one inch layer of pea gravel." 
  The question of intent is a complex one, and I can only say that that 
was not language that I would have used - in part because it isn't 
correct - this is not a drainage plane, but more accurately would have 
to be called a drainage zone - that is, a separation between the straw 
and the top of foundation.

The question is what to do about this - how to provide information that 
would both help with David's problem and guide us in the next evolution 
of codes.

Over the years I've gone back and forth a good bit on how best to 
address this issue. John makes the point that moisture moves around 
inside assemblies both as water vapor and liquid water (hopefully the 
latter only rarely and in very limited amounts - though enough water 
vapor in the presence of cold-enough condensing surfaces can produce 
plenty of liquid water). Not included in what follows are the other 
environmental issues surrounding the use of foam and various other 
moisture barriers and so forth. Figuring out what's going on with 
moisture and how to most effectively deal with it is what I'm focusing 
on, but I don't discount in any way the importance of being conscious 
of what we're using to achieve those goals and what their impacts are. 
I just don't have time or space to go into all of that now. In general 
I tend to favor the lowest tech, lowest impact EFFECTIVE strategies, 
thinking about what else might be at stake if what you're focused on 
fails to perform as required.

Here are the concerns/issues that I have thought most about...

*First and most obviously, we've always thought it important to raise 
the bales above the floor level (for either slab-on-grade or top of 
foundations that are at the same elevation as the floor) or where 
exterior slabs or floors are at the same elevation (such as porche 
slabs - we've seen porch slabs which sloped back toward the house with 
bales sitting on a moisture barrier at floor level - why did we see 
this? Because we were called to help remediate the resulting rot at the 
bottom of the wall as the bales got wet every time it rained). This is 
both to keep the bottom bales dry during construction and to deal with 
plumbing disasters, overflowing bathtubs or toilets, etc. but also has 
the benefit of providing structural attachment of netting or mesh, 
tie-downs, etc. and solid backing for plaster grounds, mesh, and 
flashing on the exterior and plaster grounds and baseboard trim on the 
interior.

*Rising damp (terminology from the UK, which I think is perfect because 
it describes what is going on with soil moisture coming up into 
buildings and assemblies by both capillary action and the movement of 
water vapor), which necessitates the inclusion of moisture barrier of 
some sort at the top of the foundation or on the slab (in the case of 
slab-on-grade construction). This deals with moisture coming up into 
the wall assembly.

*Condensation caused by cold foundations or slabs. This is what led to 
the two current practices of either having pea gravel or foam between 
the sill plates or whatever method is used to raise the bales above the 
floor or foundation. I have a basic preference for foam insulation for 
the energy conservation benefits and for separating the bales from a 
cold condensing surface. But along with these benefits come the issues 
the John raised concerning having an impervious material against the 
straw. So if liquid water is in the wall and gets down to the bottom of 
the wall, it could sit on this foam as liquid and cause problems. I 
know that some people have devised a way to cut sloping slots in the 
foam every few inches so that any significant amount of liquid water 
would drain toward the exterior plaster where it could get out or have 
some chance to dry. The idea of the pea gravel was to have support for 
the bale without creating a surface for water to collect on at the bale 
interface and to also have a capillary break to keep water that might 
accumulate at the top of foundation level (on top of the moisture 
barrier) from wicking up and wetting the straw. And of course this also 
allows more movement of water vapor in the entire assembly - which is 
either good or bad depending on how much and where the moisture is 
coming from and where it's going.

*Desire to have adequate strength for seismic areas and height of 
elevation above top of foundation/floor level has led to the use of 
4x4s (roughly 3-1/2" x 3-1/2" or 89 x 89 mm) for sill plates to the 
interior and exterior edges of the bales. This actually allows for 
different strategies, including, if one wanted to do so, a combination 
of foam at the bottom and gravel on top of the foam. This could be 
further refined to have the foam insulation fill the full height of the 
sill plates for the inner half of the space between the plates and the 
pea gravel fill the upper space on the exterior side. You could put a 
layer of 2" thick insulation across the whole space at the bottom and 
then a second piece of 1-1/2" thick insulation on the interior half of 
the space, filling the rest with pea gravel. This would give you pea 
gravel for drainage where it's most likely that liquid water would 
occur while providing good insulation to the overall assembly.

And obviously, there's are many other possible strategies and 
materials. Years ago I suggested using a clay-based oil absorbent 
material (it's the same as kitty litter - the stuff used in cat boxes, 
only you can get it in much larger, less expensive quantities) instead 
of pea gravel as the fill between sill plates since it has the capacity 
to absorb and chemically bind a fair amount of water. Of course at some 
point it would reach its capacity to hold moisture and they be much 
like other fillers.

Perhaps the design I suggested above - with the combination of foam and 
pea gravel would satisfy the building official. Eventually we'll need 
to get this sorted out.

That's my two and a half cents for today...

David Eisenberg



- -----Original Message-----
From: John Swearingen john.skillfulmeans@...
To: GSBN GSBN@...; david@...
Sent: Wed, 12 Dec 2007 9:10 am
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

We've supported the use of pea-gravel or some other broken plane, not
because we think the wall will be drenched with water, but based on our
observation of vapor migration and accumulation through bales.  Here's 
our
reasoning:

    - Vapor is continually moving around inside a bale wall as 
temperature
    conditions change. Many observations have been made of considerable 
diurnal
    movement of moisture within a bale wall, and significant 
differentials in
   humidity between the top and bottoms of a wall.
   - It's easily observed that as moisture migrates through a bale it is
   prone to stop and accumulate at any impermeable surface, and reach a
    concentration where rotting will occur. This is why we avoid vapor 
barriers
    on the bale sides. The same conditions can occur at the tops and 
bottoms of
   a wall.
   - Bear in mind, also that the sills are at the bottom of the wall
    where the most wetting occurs from direct rain and rain splash from 
the
    ground.  Some of this moisture will initially migrate to the bottom 
of the
    wall by gravity, especially in conditions of cold rain.  As David 
Arkin is
   wont to say, good boots, good hat, etc.
    - Some moisture may come from the footings: even though there might 
be
    some vapor barrier in place, it is often imperfect due to foundation 
design
   and execution.
    - Leaks do occur  around windows and cracks, and gravel does provide 
a
   path for dissipating moisture.
   - Accumulated rot in one place, the bottom of the bales, could
   compromise the integrity of the wall.

I understand that many of us are very, ah, fixated, on R-values and
buttoning up our coats.  I would not trade increased insulation for
cautious vapor management. We typically use two 4x plates of wood, 
which is
good for at least R-10---slightly low but not so far from optimal for
horizontal insulation when located low in the building shell, in our
climate.  We have also used, in colder climates, a scheme we learned 
from
Ken and Polly, simply alternating strips of rigid insulation with 
channels
of pea gravel, so you can get another 4-5" of rigid down there and make 
Al
Gore a little happier...

John "Gore-Techs" Swearingen

On Dec 11, 2007 9:37 PM, Jeff Ruppert jeff@... wrote:

> David and Anni (or Catherine et al),
>
> I completely agree with your questioning of this requirement. In our 
dry
> environment, we use all sorts of materials between the sills, with 
fine
> results.
>
> IMHO, this brings up the ever-present issues related to what we 
codify.
> Any mention of specific materials makes things like this prescriptive,
> not open to performance qualifications, nor the ability to prove 
intent,
> since no accompanying explanation of intent is present. Any future
> attempts to codify bale construction techniques should have 
accompanying
> intentions. There are too many environments and situations that will
> arise conflicting with any codification of our work.
>
> The recent work by Martin Hammer and everyone else in the past has 
been
> wonderful, but I really think we can do better and qualify our intent,
> just as other parts of the code include. There are accompanying text 
of
> intent for code structures in Canada (B.C.) and whole sections of the
> I.B.C. that have intent documents.
>
> Anything we do with regards to codes will serve us better by including
> our intentions so those of us in questionable circumstances can 
benefit
> from any contributing work in these areas.
>
> Jeff
>
>
> Catherine Wanek wrote:
> > I am forwarding this inquiry from the California Straw Building
> > Association (CASBA) list from award-winning architects David Arkin &amp;
> > Anni Tilt. Perhaps this will stimulate discussion on the GSBN 
e-waves.
> > -Cat
> >
> >> From: "David Arkin, AIA" david@...
> >> Date: Tue, 11 Dec 2007 17:21:39 -0800
> >> Subject: CASBA_Mem Pea Gravel
> >> Fellow CASBAnauts (CASBAnuts?):
> >>
> >> We haven't used pea gravel between our sill plates for some time 
now,
> >> using rigid insulation instead. My opinion is that if a bale wall 
has
> >> enough water in it to need 'drainage' (from any source), those 
bales
> >> are goners.
> >>
> >> The building official in Sonoma is citing it's recommendation in
> >> SB332 as a good enough reason to require that it be there. SB332
> >> says, "There shall also be a drainage plane between the straw and 
the
> >> top of the foundation, such as a one inch layer of pea gravel." 
Does
> >> anyone know of the intent of this?
> >>
> >> More importantly, does anyone know of any testing as to why this
> >> might (or might not) be a good idea?
> >>
> >> Your thoughts (and/or Holiday Greetings) always appreciated,
> >>
> >> David and Anni
> >>
> >> * * * * *
> >> Arkin Tilt Architects
> >> Ecological Planning &amp; Design
> >>
> >> David Arkin, AIA, Architect
> >> LEED Accredited Professional
> >> CA #C22459/NV #5030
> >>
> >> 1101 8th St. #180, Berkeley, CA 94710
> >> 510/528-9830
> >> www.arkintilt.com
> >>
> >> "There is no way to peace. Peace is the way."
> >> =E2=80=94 A. J. Muste
________________________________________________________________________
More new features than ever.  Check out the new AOL Mail ! - 
<a  target="_blank" href="http://webmail.aol.com";>http://webmail.aol.com</a>


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

Date: 12 Dec 2007 14:32:12 -0500
From: jswearingen@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

As long as we're going to full bandwidth on this, let's get into the issue
of drainage plain vs moisture barrier, and the subject of detailing,
something that DE touches on, but doesn't resolve.  As he said, it could be
an issue with our beloved Sonoma County building department, which often had
creative interpretations of code issues.

The moisture barrier part...checking rising damp, is straightforward. There
are two approaches, the capillary break (pea gravel) and the moisture
barrier (tar, paper, bituthane).  We use both--a moisture barrier under pea
gravel.  We prefer a liquid-applied "tar" because typically this is an area
that wasn't covered by the plastic vapor barrier that went under the slab.
It's a low tech and high tolerance issue--ie it doesn't have to be done to
perfection.

"Drainage plane" is, to me at least, a confusing term, and seems to imply
that there's a bunch of water to be drained.  Usually, a drainage plane is
designed to keep water from getting deeper into the building envelope, as
with a rain screen, or a drainage mat under a roof.

In this case, though, if the "drainage plane" is seeing any water, the game
is already over--moisture has come from higher up the wall, and I guess it's
purpose is to keep the foundation from getting wet?  Help me on this one!

And a note on detailing:  if it's not detailed to drain properly, this
"drainage plane" is actually more properly called a "moisture collection
basin", or MCB.  And if the purpose is to drain the wall, where are you
draining it to, and how does that help your building?

The question I've been asking recently is:  If your walls are getting so wet
that the gravel is taking on water, wouldn't you want to know about it?  I
mean, some damage is very likely occurring, and the sooner you find out the
less damage there will be.

We have previously detailed walls to discretely deposit their moisture to
the outside, thereby saving expensive insurance claims for varnished floors
and mold in the walls. A few months ago, Dan, Dietmar and I examined an
owner-built building that had extensive leakage through cracks on the
rain-exposed side of the building at the second floor.  The owners
eventually noticed the problem on the ground floor when water puddled after
large storms. . In the meantime, the plywood box beam above was already
seriously rotted.

This caused me to think...hmmm, if that water were going somewhere that the
occupants would have noticed earlier, the problem could have been nipped in
the bud.  What is the down side of detailing so that the MCB drains only to
the inside?

Eh?

Oh, yeah....  What does David Arkin tell the building department?  I think
two of the suggestions so far would work...(1) alternating strips of
insulation and gravel, (2) insulation below gravel.  I wouldn't favor
David's suggestion of (3) insulation on one side, gravel on the other,
because of the issue of putting bales on an impermeable surface.

John "What's that funny Smell?  Swearingen





On Dec 12, 2007 10:51 AM, David Eisenberg strawnet@... wrote:

> Hi all,
>
> There are several excellent points already made here:
>
> - that prescriptive requirements, whatever they might be, are typically
> limiting and not always appropriate, especially in the hands of
> designers or code officials with limited understanding of particular
> systems, materials or methods of construction,
>
> - that in this case, we actually don't have research and testing
> results to rely on for this,
>
> - that there are a number of competing concerns wanting to be addressed
> and probably an even greater number of theories and strategies
> competing to meet them,
>
> - that including intent is critically important in writing codes,
> though missing more often than not in most codes (this should not be a
> deterrent to us getting it right going forward),
>
> - that there are at least a couple of methods (with some variations)
> that predominate now - pea gravel or something equivalent and rigid
> foam insulation,
>
> - and of course, there is the first point, that David Arkin and company
> have a particular problem at present and have asked for some help...
>
> The language "There shall also be a drainage plane between the straw
> and the top of the foundation, such as a one inch layer of pea gravel."
>  The question of intent is a complex one, and I can only say that that
> was not language that I would have used - in part because it isn't
> correct - this is not a drainage plane, but more accurately would have
> to be called a drainage zone - that is, a separation between the straw
> and the top of foundation.
>
> The question is what to do about this - how to provide information that
> would both help with David's problem and guide us in the next evolution
> of codes.
>
> Over the years I've gone back and forth a good bit on how best to
> address this issue. John makes the point that moisture moves around
> inside assemblies both as water vapor and liquid water (hopefully the
> latter only rarely and in very limited amounts - though enough water
> vapor in the presence of cold-enough condensing surfaces can produce
> plenty of liquid water). Not included in what follows are the other
> environmental issues surrounding the use of foam and various other
> moisture barriers and so forth. Figuring out what's going on with
> moisture and how to most effectively deal with it is what I'm focusing
> on, but I don't discount in any way the importance of being conscious
> of what we're using to achieve those goals and what their impacts are.
> I just don't have time or space to go into all of that now. In general
> I tend to favor the lowest tech, lowest impact EFFECTIVE strategies,
> thinking about what else might be at stake if what you're focused on
> fails to perform as required.
>
> Here are the concerns/issues that I have thought most about...
>
> *First and most obviously, we've always thought it important to raise
> the bales above the floor level (for either slab-on-grade or top of
> foundations that are at the same elevation as the floor) or where
> exterior slabs or floors are at the same elevation (such as porche
> slabs - we've seen porch slabs which sloped back toward the house with
> bales sitting on a moisture barrier at floor level - why did we see
> this? Because we were called to help remediate the resulting rot at the
> bottom of the wall as the bales got wet every time it rained). This is
> both to keep the bottom bales dry during construction and to deal with
> plumbing disasters, overflowing bathtubs or toilets, etc. but also has
> the benefit of providing structural attachment of netting or mesh,
> tie-downs, etc. and solid backing for plaster grounds, mesh, and
> flashing on the exterior and plaster grounds and baseboard trim on the
> interior.
>
> *Rising damp (terminology from the UK, which I think is perfect because
> it describes what is going on with soil moisture coming up into
> buildings and assemblies by both capillary action and the movement of
> water vapor), which necessitates the inclusion of moisture barrier of
> some sort at the top of the foundation or on the slab (in the case of
> slab-on-grade construction). This deals with moisture coming up into
> the wall assembly.
>
> *Condensation caused by cold foundations or slabs. This is what led to
> the two current practices of either having pea gravel or foam between
> the sill plates or whatever method is used to raise the bales above the
> floor or foundation. I have a basic preference for foam insulation for
> the energy conservation benefits and for separating the bales from a
> cold condensing surface. But along with these benefits come the issues
> the John raised concerning having an impervious material against the
> straw. So if liquid water is in the wall and gets down to the bottom of
> the wall, it could sit on this foam as liquid and cause problems. I
> know that some people have devised a way to cut sloping slots in the
> foam every few inches so that any significant amount of liquid water
> would drain toward the exterior plaster where it could get out or have
> some chance to dry. The idea of the pea gravel was to have support for
> the bale without creating a surface for water to collect on at the bale
> interface and to also have a capillary break to keep water that might
> accumulate at the top of foundation level (on top of the moisture
> barrier) from wicking up and wetting the straw. And of course this also
> allows more movement of water vapor in the entire assembly - which is
> either good or bad depending on how much and where the moisture is
> coming from and where it's going.
>
> *Desire to have adequate strength for seismic areas and height of
> elevation above top of foundation/floor level has led to the use of
> 4x4s (roughly 3-1/2" x 3-1/2" or 89 x 89 mm) for sill plates to the
> interior and exterior edges of the bales. This actually allows for
> different strategies, including, if one wanted to do so, a combination
> of foam at the bottom and gravel on top of the foam. This could be
> further refined to have the foam insulation fill the full height of the
> sill plates for the inner half of the space between the plates and the
> pea gravel fill the upper space on the exterior side. You could put a
> layer of 2" thick insulation across the whole space at the bottom and
> then a second piece of 1-1/2" thick insulation on the interior half of
> the space, filling the rest with pea gravel. This would give you pea
> gravel for drainage where it's most likely that liquid water would
> occur while providing good insulation to the overall assembly.
>
> And obviously, there's are many other possible strategies and
> materials. Years ago I suggested using a clay-based oil absorbent
> material (it's the same as kitty litter - the stuff used in cat boxes,
> only you can get it in much larger, less expensive quantities) instead
> of pea gravel as the fill between sill plates since it has the capacity
> to absorb and chemically bind a fair amount of water. Of course at some
> point it would reach its capacity to hold moisture and they be much
> like other fillers.
>
> Perhaps the design I suggested above - with the combination of foam and
> pea gravel would satisfy the building official. Eventually we'll need
> to get this sorted out.
>
> That's my two and a half cents for today...
>
> David Eisenberg
>
>
>
> -----Original Message-----
> From: John Swearingen < john.skillfulmeans@gmail.com>
> To: GSBN GSBN@...; david@...
> Sent: Wed, 12 Dec 2007 9:10 am
> Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel
>
> We've supported the use of pea-gravel or some other broken plane, not
> because we think the wall will be drenched with water, but based on our
> observation of vapor migration and accumulation through bales.  Here's
> our
> reasoning:
>
>    - Vapor is continually moving around inside a bale wall as
> temperature
>    conditions change. Many observations have been made of considerable
> diurnal
>    movement of moisture within a bale wall, and significant
> differentials in
>   humidity between the top and bottoms of a wall.
>   - It's easily observed that as moisture migrates through a bale it is
>   prone to stop and accumulate at any impermeable surface, and reach a
>    concentration where rotting will occur. This is why we avoid vapor
> barriers
>    on the bale sides. The same conditions can occur at the tops and
> bottoms of
>   a wall.
>   - Bear in mind, also that the sills are at the bottom of the wall
>    where the most wetting occurs from direct rain and rain splash from
> the
>    ground.  Some of this moisture will initially migrate to the bottom
> of the
>    wall by gravity, especially in conditions of cold rain.  As David
> Arkin is
>   wont to say, good boots, good hat, etc.
>    - Some moisture may come from the footings: even though there might
> be
>    some vapor barrier in place, it is often imperfect due to foundation
> design
>   and execution.
>    - Leaks do occur  around windows and cracks, and gravel does provide
> a
>   path for dissipating moisture.
>   - Accumulated rot in one place, the bottom of the bales, could
>   compromise the integrity of the wall.
>
> I understand that many of us are very, ah, fixated, on R-values and
> buttoning up our coats.  I would not trade increased insulation for
> cautious vapor management. We typically use two 4x plates of wood,
> which is
> good for at least R-10---slightly low but not so far from optimal for
> horizontal insulation when located low in the building shell, in our
> climate.  We have also used, in colder climates, a scheme we learned
> from
> Ken and Polly, simply alternating strips of rigid insulation with
> channels
> of pea gravel, so you can get another 4-5" of rigid down there and make
> Al
> Gore a little happier...
>
> John "Gore-Techs" Swearingen
>
> On Dec 11, 2007 9:37 PM, Jeff Ruppert jeff@... wrote:
>
> > David and Anni (or Catherine et al),
> >
> > I completely agree with your questioning of this requirement. In our
> dry
> > environment, we use all sorts of materials between the sills, with
> fine
> > results.
> >
> > IMHO, this brings up the ever-present issues related to what we
> codify.
> > Any mention of specific materials makes things like this prescriptive,
> > not open to performance qualifications, nor the ability to prove
> intent,
> > since no accompanying explanation of intent is present. Any future
> > attempts to codify bale construction techniques should have
> accompanying
> > intentions. There are too many environments and situations that will
> > arise conflicting with any codification of our work.
> >
> > The recent work by Martin Hammer and everyone else in the past has
> been
> > wonderful, but I really think we can do better and qualify our intent,
> > just as other parts of the code include. There are accompanying text
> of
> > intent for code structures in Canada (B.C.) and whole sections of the
> > I.B.C. that have intent documents.
> >
> > Anything we do with regards to codes will serve us better by including
> > our intentions so those of us in questionable circumstances can
> benefit
> > from any contributing work in these areas.
> >
> > Jeff
> >
> >
> > Catherine Wanek wrote:
> > > I am forwarding this inquiry from the California Straw Building
> > > Association (CASBA) list from award-winning architects David Arkin &amp;
> > > Anni Tilt. Perhaps this will stimulate discussion on the GSBN
> e-waves.
> > > -Cat
> > >
> > >> From: "David Arkin, AIA" david@...
> > >> Date: Tue, 11 Dec 2007 17:21:39 -0800
> > >> Subject: CASBA_Mem Pea Gravel
> > >> Fellow CASBAnauts (CASBAnuts?):
> > >>
> > >> We haven't used pea gravel between our sill plates for some time
> now,
> > >> using rigid insulation instead. My opinion is that if a bale wall
> has
> > >> enough water in it to need 'drainage' (from any source), those
> bales
> > >> are goners.
> > >>
> > >> The building official in Sonoma is citing it's recommendation in
> > >> SB332 as a good enough reason to require that it be there. SB332
> > >> says, "There shall also be a drainage plane between the straw and
> the
> > >> top of the foundation, such as a one inch layer of pea gravel."
> Does
> > >> anyone know of the intent of this?
> > >>
> > >> More importantly, does anyone know of any testing as to why this
> > >> might (or might not) be a good idea?
> > >>
> > >> Your thoughts (and/or Holiday Greetings) always appreciated,
> > >>
> > >> David and Anni
> > >>
> > >> * * * * *
> > >> Arkin Tilt Architects
> > >> Ecological Planning &amp; Design
> > >>
> > >> David Arkin, AIA, Architect
> > >> LEED Accredited Professional
> > >> CA #C22459/NV #5030
> > >>
> > >> 1101 8th St. #180, Berkeley, CA 94710
> > >> 510/528-9830
> > >> www.arkintilt.com
> > >>
> > >> "There is no way to peace. Peace is the way."
> > >> =97 A. J. Muste
> ________________________________________________________________________
> More new features than ever.  Check out the new AOL Mail ! -
> <a  target="_blank" href="http://webmail.aol.com";>http://webmail.aol.com</a>

>
>


- -- 
John Swearingen
Skillful Means, Inc.
Design and Construction
www.skillful-means.com


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Date: 12 Dec 2007 15:20:46 -0500
From: Laura Bartels laura@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

I appreciate the dialogue on all of this. For a start, perhaps the
immediate answer for David could be to use
scoria with a much higher insulation value than pea gravel if it is
available in the area, which I consider (IMHO) to be a fairly
good approach to this.

John, as for your comments about discreet drainage to the exterior of
an MCB (or the interior for that matter),
I struggle to balance that with issues around air leakage, wind driven
rain,
etc. After good design and construction, I've been having success with
using moisture sensors in strategic places (though there is the drawback
that you can't have those everywhere either). I'd like to hear what
"discreet" drainage would look like.

I did a repair on a house this spring that I had placed sensors in
about 8 years after construction.
It was a parapet style house and the leak occurred at the seal of the
roof membrane onto the collector head
before the downspout. Amazingly, the membrane was unsealed for only
3/8" along its edge.
The sensor high in the 2nd story wall picked up the moisture and they
called to have me look at it.
It would have been good if they had called much earlier, as they did
ignore for a good bit.

Thanks all for this forum and chance to chew on things like this.

Laura
>
>

Laura Bartels
GreenWeaver Inc.
P.O. Box 912, Carbondale, CO 81623
Ph 970-379-6779, Fax 970-963-0905
laura@...
www.greenweaverinc.com








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Date: 12 Dec 2007 15:30:37 -0500
From: Graeme North ecodesign@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

I don1t like solid insulation under straw walls - it looks like an area that
could sweat to me. I like the idea of insulation at that point though.

Similarly the idea of requiring drainage at that point I find quite
disturbing - if it is that wet there are other issues.

I do like the idea of a breathable mineral based insulation layer there and
have used materials such as pumice pea gravel, or possibly scoria, or
possibly vermiculite\.

Any other thoughts?


Graeme,
Graeme North Architects,
49 Matthew Road,
RD1, Warkworth,
New Zealand 0981
Ph/fax +64 (0)9  4259305

ecodesign@...
www.ecodesign.co.nz



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Date: 12 Dec 2007 16:26:32 -0500
From: David Eisenberg strawnet@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

Briefly, in response to John's comments...

I used to always start my thinking about such matters with "what
happens in a conventionally built wall or assembly? I know that long
ago I thought about the near complete lack of drainage detailing for
moisture entering typical wood framed wall assemblies. What's the
detail that lets moisture out? There typically isn't one. That doesn't
mean having one isn't a good idea! We're trying to make sure we're not
designing problems in that we could have designed out.

My suggestion for the foam on the inner half of the space a fairly
direct response to David's inquiry - which was about the rationale for
the drainage and how to provide the insulation that he'd like to have
there. It was based on how unlikely it seems that the source of liquid
water in a bale wall would be coming from the interior side. This might
be different in a hot humid climate with air conditioning, but we're
talking Northern California with its current climate. It's just hard
for me to imagine, other than at a bathroom with a tub or shower up
against that part of the wall, of a significant amount of liquid water
ending up sitting on that foam. Could happen, but as others have said,
at that point you have bigger problems. Of course, that strip of foam
could be less than half of the space as well and still give you a good
thermal break without having a large area of straw sitting on foam. You
could just put a vertical piece of 2" foam along the inside of the
interior 4x4 for instance and fill the rest of the space with other
material. I think a fill material over a layer of foam, with a smaller
width of foam insulation to the interior side should be relatively easy
to get approved.

And please don't get me wrong, I'm not a big fan of foam. I just
appreciate some aspects of what it does and does well. There are also
various types of permeable foundation drainage boards and matts that
could work in this space. And there are other materials; scoria as
Laura suggested, or pumice if either is available, and expanded clay or
shale which has been used in Europe as insulating fill under slabs and
could work for this.

All that aside, I have been a long and strong advocate of all manner of
approaches to making sure that the moisture that gets into wall
assemblies has a way to get out - all the way to the outside. I follow
the European and Canadian building science approach that assumes that
everything will get wet - that moisture will find its way in
eventually, and thus focuses attention on basic strategies to minimize
wetting but much more attention on maximizing drying, including
drainage.  I've suggested to people that they not put a sill plate
gasket under the exterior sill plate because it is likely to do what
John is talking about, which is to create a dam that would hold liquid
water in. I like some sort of flashing pan under windows that extends
all the way out beyond the exterior plaster with a drip edge. I like
head flashings over windows and complete properly lapped flashing all
the way down onto the sill flashing. Here at the bottom of the wall
this is something we should always be thinking about...how do we not
trap water and moisture in the wall? There are lots of approaches to
accomplishing this and what's best depends on lots of things.

The question of being able to tell you have a problem is an important
one, and I'm not sure that any of the things we've been talking about
here address it directly. I advocate the installation of moisture
sensors in key locations so there is a way to periodically monitor
what's going on, as Laura suggested in her post.

David

- -----Original Message-----
From: John Swearingen john.skillfulmeans@...
To: GSBN GSBN@...
Sent: Wed, 12 Dec 2007 1:14 pm
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

As long as we're going to full bandwidth on this, let's get into the
issue
of drainage plain vs moisture barrier, and the subject of detailing,
something that DE touches on, but doesn't resolve.  As he said, it
could be
an issue with our beloved Sonoma County building department, which
often had
creative interpretations of code issues.

The moisture barrier part...checking rising damp, is straightforward.
There
are two approaches, the capillary break (pea gravel) and the moisture
barrier (tar, paper, bituthane).  We use both--a moisture barrier under
pea
gravel.  We prefer a liquid-applied "tar" because typically this is an
area
that wasn't covered by the plastic vapor barrier that went under the
slab.
It's a low tech and high tolerance issue--ie it doesn't have to be done
to
perfection.

"Drainage plane" is, to me at least, a confusing term, and seems to
imply
that there's a bunch of water to be drained.  Usually, a drainage plane
is
designed to keep water from getting deeper into the building envelope,
as
with a rain screen, or a drainage mat under a roof.

In this case, though, if the "drainage plane" is seeing any water, the
game
is already over--moisture has come from higher up the wall, and I guess
it's
purpose is to keep the foundation from getting wet?  Help me on this
one!

And a note on detailing:  if it's not detailed to drain properly, this
"drainage plane" is actually more properly called a "moisture collection
basin", or MCB.  And if the purpose is to drain the wall, where are you
draining it to, and how does that help your building?

The question I've been asking recently is:  If your walls are getting
so wet
that the gravel is taking on water, wouldn't you want to know about it?
 I
mean, some damage is very likely occurring, and the sooner you find out
the
less damage there will be.

We have previously detailed walls to discretely deposit their moisture
to
the outside, thereby saving expensive insurance claims for varnished
floors
and mold in the walls. A few months ago, Dan, Dietmar and I examined an
owner-built building that had extensive leakage through cracks on the
rain-exposed side of the building at the second floor.  The owners
eventually noticed the problem on the ground floor when water puddled
after
large storms. . In the meantime, the plywood box beam above was already
seriously rotted.

This caused me to think...hmmm, if that water were going somewhere that
the
occupants would have noticed earlier, the problem could have been
nipped in
the bud.  What is the down side of detailing so that the MCB drains
only to
the inside?

Eh?

Oh, yeah....  What does David Arkin tell the building department?  I
think
two of the suggestions so far would work...(1) alternating strips of
insulation and gravel, (2) insulation below gravel.  I wouldn't favor
David's suggestion of (3) insulation on one side, gravel on the other,
because of the issue of putting bales on an impermeable surface.

John "What's that funny Smell?  Swearingen

________________________________________________________________________
More new features than ever.  Check out the new AOL Mail ! -
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----------------------------------------------------------------------

Date: 12 Dec 2007 17:49:48 -0500
From: jswearingen@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

Laura,

Drainage to the outside would be with flashing that breaks the plaster
layer.  On the bottom of the wall this would be the equivalent of a weep
screed.  On window, it's a galvanized flashing that could be described as
the exterior side of a flashing pan that is turned horizontal to make a lip
that cuts through the stucco, draining the contents of the window leakage
onto the outside face of the stucco.

I agree that the problem with moisture sensors is that you cover the entire
house. With my luck I would put them everywhere BUT where there was a leak.
Also, over time, interest in maintaining the sensors might be lost.

John "Do You Hear a Buzzing Noise?" Swearingen



On Dec 12, 2007 1:06 PM, Laura Bartels laura@... wrote:

> I appreciate the dialogue on all of this. For a start, perhaps the
> immediate answer for David could be to use
> scoria with a much higher insulation value than pea gravel if it is
> available in the area, which I consider (IMHO) to be a fairly
> good approach to this.
>
> John, as for your comments about discreet drainage to the exterior of
> an MCB (or the interior for that matter),
> I struggle to balance that with issues around air leakage, wind driven
> rain,
> etc. After good design and construction, I've been having success with
> using moisture sensors in strategic places (though there is the drawback
> that you can't have those everywhere either). I'd like to hear what
> "discreet" drainage would look like.
>
> I did a repair on a house this spring that I had placed sensors in
> about 8 years after construction.
> It was a parapet style house and the leak occurred at the seal of the
> roof membrane onto the collector head
> before the downspout. Amazingly, the membrane was unsealed for only
> 3/8" along its edge.
> The sensor high in the 2nd story wall picked up the moisture and they
> called to have me look at it.
> It would have been good if they had called much earlier, as they did
> ignore for a good bit.
>
> Thanks all for this forum and chance to chew on things like this.
>
> Laura
> >
> >
>
> Laura Bartels
> GreenWeaver Inc.
> P.O. Box 912, Carbondale, CO 81623
> Ph 970-379-6779, Fax 970-963-0905
> laura@...
> www.greenweaverinc.com
>
>
>
>
>
>
>
>
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>
>


- --
John Swearingen
Skillful Means, Inc.
Design and Construction
www.skillful-means.com


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Date: 12 Dec 2007 19:34:50 -0500
From: Mark Piepkorn mark@...
Subject: Fwd: Re: [nbne] Fwd: Re: Pea Gravel

I forwarded this discussion to a Northeast-region group of
practitioners. A question:

>Date: Wed, 12 Dec 2007 16:58:13 -0800 (PST)
>From: David Lanfear david@...
>
>Pardon me if you've already covered what I'm going to say. Roxul
>drainboard is made from a waste product (slag). It insulates well
>and efficiently drains water.





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

Date: 12 Dec 2007 20:29:15 -0500
From: David Eisenberg strawnet@...
Subject: Re: GSBN:Fwd: Re: [nbne] Fwd: Re: Pea Gravel

Thanks Mark,

I thought about Roxul - I think it's a good material, but I didn't
mention it because I remembered that it's hydrophobic - so it won't
absorb or hold water - which could be good, but doesn't seem to meet
the need of a true horizontal drainboard in this case, if the water
just puddled on top of it, which I think it would. It may well be
better than foam, though, though perhaps harder to find. I just looked
at their webiste:  <a  target="_blank" href="http://www.roxul.com/sw53876.asp";>http://www.roxul.com/sw53876.asp</a>  and see you can
download technical info and a brochure.

David


- -----Original Message-----
From: Mark Piepkorn mark@...
To: GSBN GSBN@...
Sent: Wed, 12 Dec 2007 6:21 pm
Subject: GSBN:Fwd: Re: [nbne] Fwd: Re: Pea Gravel

I forwarded this discussion to a Northeast-region group of
practitioners. A question:

>Date: Wed, 12 Dec 2007 16:58:13 -0800 (PST)
>From: David Lanfear david@...
>
>Pardon me if you've already covered what I'm going to say. Roxul
>drainboard is made from a waste product (slag). It insulates well
>and efficiently drains water.

________________________________________________________________________
More new features than ever.  Check out the new AOL Mail ! -
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----------------------------------------------------------------------

Date: 12 Dec 2007 21:19:03 -0500
From: Chris Magwood cmagwood@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

I love it when we get all fired up on these detail questions.

What to do in the sills has always been a concern of mine. Somebody
mentioned Roxul drainboard, which is what I used to use until it was
pointed out to me that it only drains when placed vertically. In a
horizontal application, it holds water really really well.

This year, I used two different materials that I really liked. David
mentioned that foam, while not always the most desirable product, has
qualities that suit this application. I saved up foam meat and
vegetable trays from home last winter, and then had enough to crumble
up and fill the sills for half of a large building. Not always do-
able, I agree, but it was free, provided insulation, but not that
solid foam "barrier" for those who worry about having some drainage.

The more practical material I used this year was zebra mussel shells.
I was impressed with the use of big mussel shells in Denmark. We
don't have them here, but we do have big troubles with invasive zebra
mussels, and their shells made a very good fill in the sills. Enough
trapped air to be decent insulation (better than pea gravel or sand),
but enough space to drain a bit of moisture and they won't allow any
wicking.

Of course, no code would have crumbled meat trays or zebra mussel
shells written in. But when I explained to the building official what
the intent was, he was quite amenable to both materials.

In terms of using that space for "drainage" I do embed those little
brick drains about every 4-8 feet on the exterior sill. Basically I
put one in where I have a joint between pieces of wood for the sill.
I've never seen or heard of anything weeping out of these, and don't
know how effective they would actually be for various amounts of
water, but for a couple of bucks I've been doing it just to feel better.

As an "aside" to this sill plate discussion, I have been tending
toward using foundation systems that are not monolithic under the
bales, i.e., two rows of earthbags or two rows of narrow concrete
blocks on a rubble trench or on a poured concrete footing. This
leaves between 4-12 inches of space in the centre of the wall
(depending on the material I'm using and bale size/orientation). This
wider space makes for great insulation without having to resort to
foam on the exterior of the foundation, and plenty of drainage should
that ever be necessary. Less concrete, too.

Thanks all for pitching in to these great discussions.

Chris



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

Date: 12 Dec 2007 22:05:25 -0500
From: Tom Hahn tomhahn@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

David, Mark, Chris, et. al. - My viewpoint has always been that this
is mostly an issue of separation from rising damp and condensation,
though it appears the code section was not written in such a way...
Building in Arizona (yes, I know, we get away with everything here...
at least climatically speaking), we have never been overly concerned
about moisture "coming down inside the walls", but have had occasion
(on flood-irrigated lots, mostly... don't ask, you'd be appalled...)
where a slab might get saturated over a short period of time.

First, a bit of support for the drainage mat/board idea...

The retaining wall drainage mat/board has many advantages... As we
all know, the boards intentional use is to take away the "hydrostatic
pressure" at the moisture/vapor barrier on the backside of a
retaining wall.  Most  accomplish this by allowing moisture to pass
through their "earth-side" face, and then allow it to "fall through"
them in their vertical orientation, while some type of nominal
moisture/vapor barrier on the "wall-side" keeps the moisture from
passing all the way through (a la Roxul's product).  The other major
challenge they have to meet is not being crushed by the mass of earth
behind the retaining wall, to the point where they can no longer
drain, and so they have an internal rigidity that doesn't, at the
same time, defeat the drainage capability.  I think this situation is
not dissimilar to the conditions at the bottom of a bale wall
(especially a load-bearing one...), where the downward pressure of
the bales has to be supported between the sill-plates, and, if sloped
a small amount, the drainage board can let moisture into it's upper
surface and drain it out along it's lower surface.

But now for the "killer app" idea...

Chris' recalling of his "shredded" food containers made me think of a
similar, perhaps more widely available, alternative... All those
billions of "packing peanuts" that seem to be such a scourge to
landfills and recyclers alike.  Typically, these are "extruded"
polystyrene (XPS), and so are in theory impervious to water.  But,
poured into the space between sills, they would provide the perfect
open "drainage plane", would be highly insulative, and also be well
able to resist the pressure of the bales above.  Now, the only
caution is to make sure your "recovered" packing peanuts are all
petro-plastic based.  Because of the push of those "green meanies"
(is that what they call us?), more and more of these peanuts are
bio-based plastics which will bio-degrade, or even melt in your mouth.

So, who would have thought one of the stars of bad environmental
practice, the plastic-foam packing peanut, might come to the rescue
of a star of the natural building movement, straw-bale.

Just a thought...
Tom Hahn




>I love it when we get all fired up on these detail questions.
>
>What to do in the sills has always been a concern of mine. Somebody
>mentioned Roxul drainboard, which is what I used to use until it was
>pointed out to me that it only drains when placed vertically. In a
>horizontal application, it holds water really really well.
>
>This year, I used two different materials that I really liked. David
>mentioned that foam, while not always the most desirable product, has
>qualities that suit this application. I saved up foam meat and
>vegetable trays from home last winter, and then had enough to crumble
>up and fill the sills for half of a large building. Not always do-
>able, I agree, but it was free, provided insulation, but not that
>solid foam "barrier" for those who worry about having some drainage.
>
>The more practical material I used this year was zebra mussel shells.
>I was impressed with the use of big mussel shells in Denmark. We
>don't have them here, but we do have big troubles with invasive zebra
>mussels, and their shells made a very good fill in the sills. Enough
>trapped air to be decent insulation (better than pea gravel or sand),
>but enough space to drain a bit of moisture and they won't allow any
>wicking.
>
>Of course, no code would have crumbled meat trays or zebra mussel
>shells written in. But when I explained to the building official what
>the intent was, he was quite amenable to both materials.
>
>In terms of using that space for "drainage" I do embed those little
>brick drains about every 4-8 feet on the exterior sill. Basically I
>put one in where I have a joint between pieces of wood for the sill.
>I've never seen or heard of anything weeping out of these, and don't
>know how effective they would actually be for various amounts of
>water, but for a couple of bucks I've been doing it just to feel better.
>
>As an "aside" to this sill plate discussion, I have been tending
>toward using foundation systems that are not monolithic under the
>bales, i.e., two rows of earthbags or two rows of narrow concrete
>blocks on a rubble trench or on a poured concrete footing. This
>leaves between 4-12 inches of space in the centre of the wall
>(depending on the material I'm using and bale size/orientation). This
>wider space makes for great insulation without having to resort to
>foam on the exterior of the foundation, and plenty of drainage should
>that ever be necessary. Less concrete, too.
>
>Thanks all for pitching in to these great discussions.
>
>Chris
>
>----
>For instructions on joining, leaving, or otherwise using the GSBN
>list, send email to GSBN@...HELP in the
>SUBJECT line. ----



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Date: 12 Dec 2007 22:59:58 -0500
From: Martin Hammer mfhammer@...
Subject: Re: GSBN:Fwd: CASBA_ Pea Gravel

Hello all -

I've been silent for some time, largely due to my recent 5 weeks in
Pakistan, which I will brief you on in a future e-mail.  But about this
subject of pea gravel / capillary break / drainage plane.

For my input I start with the language from my proposed SB Appendix to the
California Building Code (status of which is the subject of another
forthcoming e-mail):

L104.6  Bale/Concrete Separation.  There shall be a moisture barrier and a
capillary break between bales and supporting concrete.  The moisture barrier
may be any durable sheet or liquid applied membrane that is impervious to
water.  The capillary break may be gravel or other material that prevents
the wicking of moisture across that material and into the bale.  Where bales
abut a concrete or masonry wall that retains earth, there shall be a
moisture barrier between that wall and the bales.

It boils down to the following goals/concepts:
1)  prevent migration of water vapor from relatively wet concrete (in
contact with relatively wet earth) to relatively dry straw. (movement
mechanism: wet to dry diffusion)
2)  provide a capillary break that prevents the migration of any liquid
water at the base of the wall into the straw. (movement mechanism: capillary
action)
3)  provide a drainage plane that keeps any liquid water at the base of the
wall from direct contact with the straw (movement mechanisms: direct
contact, capillary action)

Sources of water:
a) ground water
b) intrusion of rainwater
c) condensation
d) interior spill (plumbing fixture, water appliance, your olympic-sized
swimming pool overflowing)

In my proposed code language I require a "moisture barrier" and a "capillary
break".  In principle I think a drainage plane is needed, but I don't
require it by name, because I think if you provide a capillary break you
also have a drainage plane. (However, for purposes of describing intent,
maybe the term should be included)

I also address the condition of bales abutting concrete that retains earth.
A moisture barrier is required, but no capillary break or drainage plane.  I
have thought that this is sufficient for this condition, but as I think
about it now, maybe there should be a capillary break/drainage plane here
also, in case of condensation or a failure in the moisture barrier.

It's interesting to look back and try to understand my own logic in this
code section.  If the logic or language is deficient, I'm open to
improvements (as always).

I agree with most of what everyone has said about the subject in the
thorough and entertaining dialogue, but will expand on or challenge a few
things.

Re: the subject of performance vs. prescriptive code language -  I believe
that depending on the issue, performance and/or prescriptive language should
be used.  If I had to pick one I would say performance, but I sometimes
favor the use of both.  By using both you're essentially saying "Here's how
(whatever) needs to perform, and here's an example of something that
provides that performance."  Is there anything wrong with satisfying both?

Re: intent included in code language - To varying degrees, performance
language at least implies intent, and in some cases is identical.  I think
conveying intent in the language is a good idea.  If it becomes too
unwieldy, there could be (and often is) a commentary that accompanies and
supports the code.

Re: the drainage plane becoming a "moisture collection basin" (J.S.) - With
normal detailing at the bottom plates, this won't happen.  Well before it
could fill up and reach straw, it would weep to the inside (good for
detection) and/or outside (good for release and/or detection).  And I do
think the concept of a drainage plane is legitimate here.  Yes water could
come from above and you'd have bigger problems.  But it could also come from
outside, near the exterior surface or at the bottom of the wall, or a flood
source from inside.  Even from condensation on the top surface of the
supporting concrete (slab/foundation).  (As an aside, I've been running
water supply pipes laterally in this space between the bottom plates, and if
they leak there in a drainage plane, they would presumably do little harm.)
In all these cases a drainage plane keeps the bales away from liquid water.

That said, in Pakistan Darcey Donovan and I are now using gravel bag
foundations with no drainage plane between the top layer of bags and the
bottom of the first course of bales.  We are painting a moisture barrier on
the top course of gravel bags (which are capillary breaks themselves, albeit
below the moisture barrier) and are dipping the bottom of the first course
of bales in clay slip as insurance in case moisture occurs at that interface
short term.  In Pakistan we are well outside the jurisdiction of the
California code and must answer only to our sense of good practice, and
occasionally the Taliban.  (I'm trying to keep both my sense of humor and my
drainage planes dry.)

I like many of the ideas shared by everyone for this small but important
space between bottom plates.  Like rock that contains air and is more
insulating, or a small thickness of foam insulation against the inside plate
with gravel in the remainder, or layers of gravel and insulation.

Also, from John Swearingen's first e-mail on this subject, I think his
"Gore-Techs" sign-off is one of his best in a long line of clever and
occasionally brilliant puns.

Glad to be back in the discussion.

Martin (Give me a capillary break!) Hammer






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