[Cob] cob vs.adobe R values

[Monica]

Now I'm confused.  Why would the "worst" cob (low straw content) have, or start at, a lower R value than adobe (.35 vs. .38)?  Perhaps you were estimating on the cob, or does this instead have something to do with the thermal mass thing?  (ie, the straw waters down the thermal mass qualities of the cob).  My confusion is because i was always under the impression that thermal mass isn't a factor used in computing R values. 

Monica 


On Jul 20, 2010, at 1:00 PM, coblist-request at deatech.com wrote:

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> Today's Topics:
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>   1. Re: DSCN0313 (Shannon Dealy)
>   2. codes (Damon Howell)
>   3. Cob on a north slope CA mass inefficiency (Charmaine Taylor)
>   4. Re: codes (Janet Standeford)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 19 Jul 2010 12:03:43 -0700 (PDT)
> From: Shannon Dealy <dealy at deatech.com>
> Subject: Re: [Cob] DSCN0313
> To: Cob List <coblist at deatech.com>
> Message-ID: <Pine.LNX.4.64.1007191128490.7243 at nashapur.deatech.com>
> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> 
> On Sun, 18 Jul 2010, Henry Raduazo wrote:
> 
>> (Pictures must be requested off list)
>> Janet: I believe that cob has an R-value of 1 per inch so 24 inches thick 
>> would be R-24. I am not sure where I read that, but R-value is beside the 
> [snip]
> 
> Sorry, but the R-value of cob IS NOT anywhere near 1 per inch.
> 
> This keeps showing up over the years, but the original discussion of it as 
> I recall showed this claim to be seriously flawed as the measurements did 
> not adequately account for the effects of thermal mass.  Depending on your 
> mix it will most likely be somewhere between R 0.35 and 0.5 (for a really 
> high straw mix).
> 
> R-values of some other materials for comparison:
> 
>    Concrete:           0.08 per inch
>    Low density brick:  0.20 per inch
>    Stucco:             0.20 per inch
>    Adobe:              0.38 per inch
>    Most hard woods:    0.90 per inch
>    Most soft woods:    1.25 per inch
> 
> It should be fairly obvious to anyone who has worked with these materials 
> that cob cannot possibly have an R-value anywhere near as high as a 
> typical hard wood, and that it is at least somewhat comparable to standard 
> adobe.
> 
> Having said this, it is important to remember that the effects of thermal 
> mass can radically alter the energy equation for a building to the point 
> that depending on the location and time of year, the thermal mass may be 
> far more important for energy savings than the R-value.  Unfortunately the 
> codes have not historically recognized this fact, so it may be necessary 
> to beat your building officials over the head with hard engineering 
> mathematics and data in order to make use of this.
> 
> Of course, your best choice for anywhere that extreme temperatures can 
> occur is a combination of insulation and thermal mass which usually would
> require some kind of hybrid wall system for at least part of the 
> structure such as cob-bale.
> 
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
> Phone: (800) 467-5820 |          - Natural Building Instruction -
>    or: (541) 929-4089 |                  www.deatech.com
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Mon, 19 Jul 2010 16:46:21 -0400
> From: Damon Howell <dhowell at pickensprogress.com>
> Subject: [Cob] codes
> To: coblist at deatech.com
> Message-ID: <24001B86-6A87-45F0-80EF-066CEC7E28C0 at pickensprogress.com>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
> 
> Janet,
> 	I would love to read the codes you mentioned. I've read the New  
> Mexico Adobe codes and noticed they're not much relevant to cob. I  
> think it is so awesome that you are making such headway and possibly  
> clearing a lot of the path for the rest of us. I remember having the  
> building inspector come to my place, to inspect a storage building.  
> He saw my cob storage building and said, "What's that up there?" I  
> said, "A cob house." He just shrugged his shoulders, went "huh,"  
> hopped in his truck and left. He wasn't even interested enough to  
> walk up close to see if I was doing anything I shouldn't be. I got  
> the impression that he figured he couldn't inspect something he knew  
> nothing about.
> 
> Damon in Ga, USA
> 
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Mon, 19 Jul 2010 13:34:57 -0700
> From: Charmaine Taylor <dirtcheapbuilderbooks at gmail.com>
> Subject: [Cob] Cob on a north slope CA mass inefficiency
> To: coblist at deatech.com
> Message-ID:
> 	<AANLkTimjRUC1fdJm4sv_TP7zdMIh-vpSM2YVD0hrwalx at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Janet I am happy  you are feeling so strong on your decision, and I
> must hope you get a wide swing of temps in summer and winter there,
> because even sandy clay is going to be poor  to hold mass heat.
> Cob/adobe  it is 1/4 R per INCH-- so 4 inches of cob =1R.   You may be
> able to keep the home warm at just  330 ft from your ( and animal)
> body heat and occupation, but  I  think you are being over positive on
> this.
> 
> I am not an expert in cob, but I am familiar with your climate, what
> others have done, and what I have read.
> 
> Remember in the  way back times (1200-1800s)  people in cob homes in
> UK/Europe kept a fire going all the time,  year round to keep warm
> inside cause there is no swing of temps there to maintain heat in the
> mass.   do you want that much wood smoke?
> 
> Or can you plan a masonry stove too?   see  http://mha-net.org <<<
> Masonry Stove Builders   for great designs and info, and builders to
> talk to.  they are pricey to have built, but you can do it yourself
> too with a clear plan.  I will send you some info off list.
> 
> In his cinva adobe block home in NM  Sean Sands did an adobe brick
> masonry stove right up the center of his tiny home, and all the roof
> beams  were  radiated off of that for the round  roof shape.  this is
> shown in the DVD A sampler of Alternative Homes.
> 
>  Please do plan for as much  passive solar via window glass if you
> can, or build a  glass trombe design wall outside the  cob home  (
> full of potted plants, shrubs)   using a series of slider doors in a
> half circle and some framing.
> 
> I know how strong you feel, and your enthusiasm will carry you far,
> but do really  go sit in an uninsulated home somewhere this winter, or
> just a plain barn,  and try to be comfortable for several days with no
> heat on, only a fireplace.  try to test your theory.
> 
> No one says build with bales, but  plan plan plan for your best
> design.I do know of people who had a   light straw clay home built  by
> Robert La Porte, and were sorry-at 12-15" thick  it was way too cold
> all the time, so those walls did not keep them comfortable even with
> the straw content.  R22 is tossed around for a 12" +  LSC wall, but I
> think that is for a milder climate than you are in.    Maybe Barbara
> Roemer  can pipe in with her temps there in North Fork CA.   it was
> blazing hot in the summer while I was there, and they get a lot of
> snow too in winter.
> -- 
> Charmaine Taylor Publishing
> www.kidneycancerwarrior.blogspot.com
> http://www.dirtcheapbuilder.com
> 
> www. http://loveforlife.com.au/node/5917 << woodland cordwood hobbit
> home in Wales
> 
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Mon, 19 Jul 2010 22:09:16 -0700
> From: Janet Standeford <janet.standeford at gmail.com>
> Subject: Re: [Cob] codes
> To: coblist at deatech.com
> Message-ID: <4C452F7C.3030508 at gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> http://ecodes.biz/ecodes_support/free_resources/Oregon/10_Structural/10_PDFs/Chapter%2021_Masonry.pdf
> 
> Code: 2109.3.1
> 
> This is only part of what I remember reading and I am trying to find the 
> full code. It says the test samples must be 4"x4"x4".
> 
> Janet Standeford OR
> www.buildingnaturally.info (Owned by you)
> A resource for healthy homes.
> 
> 
> 
> On 7/19/2010 1:46 PM, Damon Howell wrote:
>> Janet,
>>    I would love to read the codes you mentioned. I've read the New 
>> Mexico Adobe codes and noticed they're not much relevant to cob. I 
>> think it is so awesome that you are making such headway and possibly 
>> clearing a lot of the path for the rest of us. I remember having the 
>> building inspector come to my place, to inspect a storage building. He 
>> saw my cob storage building and said, "What's that up there?" I said, 
>> "A cob house." He just shrugged his shoulders, went "huh," hopped in 
>> his truck and left. He wasn't even interested enough to walk up close 
>> to see if I was doing anything I shouldn't be. I got the impression 
>> that he figured he couldn't inspect something he knew nothing about.
>> 
>> Damon in Ga, USA
>> 
>> 
>> _______________________________________________
>> Coblist mailing list
>> Coblist at deatech.com
>> http://www.deatech.com/mailman/listinfo/coblist
>> 
> 
> 
> 
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> End of Coblist Digest, Vol 8, Issue 130
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