[Cob] R value of cob vs strawbale

[Henry Raduazo]

Deborah: if you have the ability to build a three foot thick cob wall then you have the ability to build a hybrid. 
	Also, there are some good reasons why you might not want to build a three foot thick cob wall besides the fact that you will be mixing and placing tons of extra material. I once rented a room in an adobe house for a couple of weeks and the owner advised me that the room was quite comfortable until the end of summer because the massive walls tended to average out the cooler night time temperatures and the warmer day time temperatures. However, by the end of the summer when the entire biomass of the walls became heated up then no amount of air conditioning could lower the temperature of that room to what city dwellers in air conditioned houses consider comfortable.

 	There are several methods that can be used to construct a hybrid structure. The first photo which I sent you shows co-forming straw bale and cob walls together. The disadvantage of this construction method is that during construction you must be meticulous about protecting the straw bales from moisture. That usually means constructing a temporary roof over your building cite and maintaining that roof until the permanent roof is in place. The first photo is from Cae Maybon. (My apology for the spelling I do not speak Welch. I have not been back to Whales since the construction, but I understand from an indirect source that the owner is very happy with the thermal properties of the building. Note there is lots of solar heat, but no attempt to air condition the structure.
	An alternative method, which I highly recommend, is to build the cob wall first and place deadman anchors in the wall during construction so that you can attach the straw bales after the permanent roof is in place. Cob is very forgiving if it gets rained on straw bales are not. 
	You can also drill holes through walls of an existing cob structure and place one deadman inside of the cob structure and attach another deadman on the outside surface of the straw bales. Both deadman anchors would then be covered with earth plaster and then lime paint or plaster.
	A third system that I used to build a hybrid structure in Washington, DC area consisted of building straw bale walls and temporarily supporting a roof on the bales while cob walls were being built on the inside of the structure. This came about because of an odd situation. I had a large crew that wanted to learn straw bale on a small structure. So, I pre-manufactured the roof framing. Then during the workshop we built the straw bale walls and using picnic tables as scaffolding I had my crew just pick up the roof framing and place it on the walls. I attach diagonal bracing from the roof framing to the ground to hold the roof in place while we added a plywood and membrane surfacing. Later with the roof braced on top of the straw bales we constructed our cob walls at a relatively leisurely pace.
	A final variation must be mentioned for construction methods 1 and 2 but not for method #3. and that is the use of half bales. One problem with the hybrid structure is that you are losing a lot of interior space to wall thickness. This is particularly true if you are using three string bales. To deal with this problem you will need to built a bale compression jig. The jig consisted of a vertical post connected to any horizontal surface and an 8 foot 2" x 4" stud pivotally connected at varying heights to the vertical post. To use the jig you wrapped one or more strings around a bale then placed it against the post and compressed it by putting weight on the 2" x 4" stud. You can then tie the strings at the desired bale height to produce a bale with 4 strings tying it together. You would then place this bale now tied with 4 strings on a cutting jig and chain saw it in half to produce two bales of 1/2 the normal thickness. These half bale are then secured to the cob wall and plastered to form the outside wall of your cob structure. 
	This is something that nearly anyone can do. Please be careful with the chain saw. Use only experienced chain saw operators and wear a dust mask.
	 if anyone wants them, I have pictures of everything except the jigs and the chainsaw for compressing and cutting straw bales.

Ed


On Feb 10, 2015, at 11:51 AM, Deborah Denmark wrote:

> Yes, Hi Dorethy, I read your ebook and I have had Iantos book for a long
> time now. Read it cover to cover when I first got it and will be reading it
> again soon. I had thought about putting the strawbales between two thick
> layers of cob. It is the wood framing that I don't have the skills and
> quite frankly the inclination to attempt so the two thick walls of cob
> might be a good solution for me. I know 'mud' very well, I feel good about
> 'mud'.
> 
> On Tue, Feb 10, 2015 at 10:48 AM, Dorethy Hancock <
> dorethy at centeroftherainbow.com> wrote:
> 
>> Deborah,
>> Our temps in Kansas are a bit more severe than you mention (minus 20
>> possible in winter, to 104 in summer--both for short periods, but
>> still...), and I built my entire cob house with insulation of straw bales
>> sandwiched between 5-6 inches of cob.  Saying "load-bearing cob" is
>> redundant, because, of course, cob is load-bearing just by its mass.  But
>> it is not, of itself, insulative, so you need the strawbales inside.  Your
>> interior walls can be strictly cob, though.  I built mine about 7 feet tall
>> and they did not meet the ceiling.  I absolutely love the strength of the
>> mass and the coziness felt inside.  I still have 5 big windows on the SE,
>> S, and SW sides for solar gain.  These need some solid cob pillars for
>> shear strength, so I built mine up slowly, so the interior of them would
>> get dry, and they're as thick as the rest of the wall which has bales
>> inside.
>> 
>> Do yourself a favor and buy Ianto Evans' book *The Hand-Sculpted House.*
>> From it you will glean *everything* you need to build this yourself--from
>> the philosophy behind it all the way down to the nitty-gritty of how to
>> test the amount of clay in your soil.  It was my "Bible" when I built.  If
>> you have other questions, I would be happy to help!
>> 
>> By the way, I published an e-book about my experience building cob *and*
>> strawbale, which you can get for $3.99 direct from this link:
>> www.smashwords.com/books/view/317540.
>> 
>> Good luck!
>> Dorethy from Kansas
>> 
>> On Tue, Feb 10, 2015 at 9:20 AM, Deborah Denmark <
>> deborahddenmark at gmail.com> wrote:
>> 
>>> Thanks everyone for your input. I was hoping to find a 3 foot thick cob
>>> wall would stand up to a strawbale for insulating qualities. I know I can
>>> build a cob wall all by myself but I don't think I have the skill to put
>>> up
>>> a strawbale wall alone. I am thinking I might be disappointed with cob
>>> exterior walls no matter how thick I made them.
>>> 
>>> On Tue, Feb 10, 2015 at 9:42 AM, Henry Raduazo <raduazo at cox.net> wrote:
>>> 
>>>> Debora:
>>>>        Why not try both. You can build a hybrid structure that uses
>>> straw
>>>> bale on the outside and load bearing cob as the interior wall thus
>>> giving
>>>> yourself both insulation where it is needed and biomass for storing
>>> solar
>>>> energy and providing a strong load bearing wall that will not compress
>>> over
>>>> time and crack your walls as some load bearing straw bale walls are
>>> known
>>>> to do..
>>>> 
>>>>        For pictures of hybrid construction send a request to me
>>>> personally because pictures are not allowed on the coblist list.
>>>> 
>>>> Ed
>>>> On Feb 9, 2015, at 2:34 PM, Deborah Denmark wrote:
>>>> 
>>>>> I have a question concerning the best way to build a north face wall
>>> in
>>>>> northern hemisphere. The south face will be built to take advantage of
>>>>> passive solar principles.
>>>>> 
>>>>> I am wondering if it would give higher R value to go with a straw bale
>>>> wall
>>>>> on the north side of the house or a cob wall that is 3 feet thick at
>>> the
>>>>> base reducing to 2 feet thick at the top of the wall (1 story high).
>>>>> 
>>>>> The winter nighttime low temps in my area average in the 20s to 30s in
>>>> the
>>>>> winter with occasional dips into the teens and less frequent dips to
>>>> single
>>>>> digits and far less frequently we get the occasional below 0 degrees
>>> F.
>>>>> 
>>>>> The winter daytime highs average in the 40s with the occasional dips
>>> of
>>>>> course similar to the nighttime dips.
>>>>> 
>>>>> The climate is also at high humidity levels most of the time as I am
>>> in a
>>>>> temperate rain forest climate in the southern Appalachian mountains.
>>>>> 
>>>>> Deborah Denmark
>>>>> Cullowhee, NC
>>>>> _______________________________________________
>>>>> Coblist mailing list
>>>>> Coblist at deatech.com
>>>>> http://www.deatech.com/mailman/listinfo/coblist
>>>> 
>>>> 
>>> 
>>> 
>>> --
>>> Deborah Denmark
>>> Cullowhee, NC
>>> 828-293-3969
>>> deborahddenmark at gmail.com
>>> https://www.tsu.co/DeborahDenmark
>>> Deborah Denmark on Facebook
>>> deborahddenmark on Skype
>>> _______________________________________________
>>> Coblist mailing list
>>> Coblist at deatech.com
>>> http://www.deatech.com/mailman/listinfo/coblist
>>> 
>> 
>> 
> 
> 
> -- 
> Deborah Denmark
> Cullowhee, NC
> 828-293-3969
> deborahddenmark at gmail.com
> https://www.tsu.co/DeborahDenmark
> Deborah Denmark on Facebook
> deborahddenmark on Skype
> _______________________________________________
> Coblist mailing list
> Coblist at deatech.com
> http://www.deatech.com/mailman/listinfo/coblist