[permaculture] Question about Earth Homes, thermal mass
newtribe at hughes.net
Fri Feb 5 18:53:28 EST 2010
I'd like to know where all these bales houses are that you have seen fail?
In 16 years of travel around the Southeast US, going to our own clients and
to many other straw bale structures, I cannot think of more than 2 that had
straw failures. In both situations there were clear reasons for the
If you are seeing such homes then I would venture to say they were probably
poorly built and would have failed regardless of the building materials
used. Crap in - crap out, as they say. Your categorization of
owner-builders does not reflect the qualities I have experienced in the
people we have worked with.
As for vapor barriers - keep them out of the walls! Natural buildings need
to breathe. Natural lime-based plasters let the wall breathe and mitigate
moisture issues inside the home.
My "one" example - which one was that? If you are referring to the Burritt
Mansion, that is a highly unconventional straw bale home. Not one people
would want to emulate for several reasons, but the fact remains, even
without the proper detailing, this straw house is 75 years old and doing
As for the other examples, the oldest ones are 16 years old and doing fine.
Granted, not much in the life of a building. In many cases the straw is
being monitored and no one is experiencing problems. My experience has been
quite different than yours, it seems. Most straw bale homeowners are very
proud of their homes.
proud owner of a Southeastern US straw bale home, 10 years and counting,
On Thu, Feb 4, 2010 at 1:33 PM, Gene Monaco <efmonaco at comcast.net> wrote:
> Being a builder I would say that both are correct.
> I have seen many many buildings that have water issues, and lots and lots
> mildew issues without even using straw. The building industry is finally
> starting to get the idea that it is best to take away the materials that
> be consumed by fungi, such as the paper on gypsum sheathing. We're seeing
> fiberglass exterior sheathing and paperless drywall.
> The issue is that even with the best laid plans, moisture has a tendency of
> working itself into wall cavities, both from the inside and the outside.
> Even without breaches in the building envelope or drainage systems, humid
> interior conditions like shower rooms will let moisture migrate into the
> wall unless there is a vapor barrier on the inside, which there almost
> is. Humidity from the outside will work its way into the wall cavity
> there is a vapor barrier on the outside. Most building details do have
> sort of vapor barrier on the outside, but not on the inside. Even when
> vapor barriers are used, they often are breached by penetrations at doors,
> windows, pipes, and fasteners. Cob, mud plaster, cement plaster, and
> drywall will all allow moisture to migrate from a zone of higher
> concentration to a zone of lower concentration.
> Moisture can even wick up through the footings into the walls. Who do you
> know that puts a vapor barrier under or on top of the footings? The most
> you ever see is a stem wall from the ground level down to the footing, with
> waterproofing on the outside of the stem wall and a foundation drain along
> the bottom of the stem wall at the top of the footing. What you have to do
> is make the building foundation system like the bottom of a boat so it
> floats in the dirt so no moisture can get in. It can be done but it is not
> easy, and certainly most mom and pop types that set out with stars in their
> eyes to build their straw bale house will not get it right. Plus, ask
> yourself, why then do they put bilge pumps in boats?
> When straw is used, it is already inoculated with fungi from its natural
> environment, which is anything but natural the way straw bales are created
> (but that is another story). Plus the bales are generally not bone dry;
> they have some moisture content. They absorb humidity from the air right
> the jobsite. Some moisture inevitably gets trapped in the wall, and if
> enough moisture is present the fungi will multiply and eat the straw. If
> that happens enough you will smell mildew. I've been in a number of straw
> bale structures that despite the best efforts of the builders smelled like
> mildew and eventually were abandoned. For the one case Katey cites, I'll
> bet there are dozens if not hundreds of others that were abandoned.
> This is not to say that Katey is wrong. If the structure is detailed AND
> built AND maintained, then all CAN be well; but in my opinion you are
> stacking the odds against you. It takes more than an architect to make it
> all work right. All it takes is an overlooked spot during construction, a
> crack in the plaster, a leaky joint in a gutter system, nail holes punched
> through the vapor barrier, or a leaky window, door jamb, plumbing
> penetration, chimney flashing, whatever you can imagine, and in the warm
> humid regions your structure will be soon on its way to toast or more
> precisely, soil.
> A great book to read that describes in excruciating detail how nature takes
> apart structures in no time is: The World Without Us by Alan Weisman. In a
> nutshell, it's the water (stupid).
> Gene Monaco
> Knoxville, TN
> Katey wrote:
> Hi Robyn,
> Are you a builder or architect? I am wondering how extensive your
> experience is. I am partner in the architect/design firm Ecoville
> ArchiTechs. We live in the Southeastern US and promote natural building
> methods. Since 1994 we have helped over 35 clients in 9 states build with
> straw bales. I have not found it to be true what you say about humidity
> straw bale homes. Humidity is not a problem. Moisture is a problem if it
> gets in your walls, just like with any building. You detail to prevent it.
> In our designs we also add a drainbed under the straw in case the bathtub
> overflows. We use a lime/clay plaster which also performs well in our
> region. And of course the Burritt Mansion in Huntsville AL is straw bale
> built in 1936, still in use today as a public building.
> We have not yet had a client who wants to build cob but we'd welcome it.
> have worked on many cob structures in the area that are doing fine but they
> are not conditioned living spaces. Some of these are going on 15 years; so
> far so good.
> On Sun, Jan 31, 2010 at 9:18 PM, Robyn Francis <erda at nor.com.au> wrote:
> > Hi
> > I live in a similar climate to SE USA: hot, muggy, humid and big rains in
> > summer and big temperature changes from day to night so condensation can
> > also be an issue. Here we need to be very careful using earth or
> > construction. I've seen numerous earthbrick/cob structures in this area
> > simply erode away with torrential rains, and know of issues with
> > buildings with humidity entering through the render and the straw
> > decomposing and becoming an ant metropolis.
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