Hello Zoub,

   Thank you Sandy for such a good explanation.   To elaborate just a little, here is a brief quote from Dr. Kris Dick's seven page document entitled

 "The scope of this project is to build two Stackwall / cordwood model walls to evaluate their thermal performance. The test walls were constructed within the Department of Biosystems Engineering Strawbale Research Facility at the University of Manitoba in Winnipeg, Manitoba, Canada. One facing North the other South. Once the walls were constructed a temporary heat source was used to provide a constant inside room temperature. Temperature measurements at the outside, middle and inside of the logs were recorded over a period of approximately three months during the winter of 2004-2005.  The difference in outside ambient temperature and inside temperature as well as the temperature gradient through the logs was used to develop the apparent R-value of the logs. Temperature measurements in the outside and inside mortar beds as well as in the insulated void between the mortar beds were recorded to develop an overall R value for the entire thermal mass.  Based on the average heat transfer of the system as well as the average change in temperature across the wall system for the data collected, the experimental RSI value was determined at 6.23 (m²K/W).

When converted into imperial units the total R-value is 35 (for a 24" wall) or 1.47 R- per inch."  end quote

 This means that for a cordwood wall which has been in place for a heating season and had any primary checks sealed and any log loosening dealt with (Permachink/Log Jam caulk) that the R-value per inch of a cordwood wall (log end, mortar matrix and insulation--in this case sawdust & lime) is 1.47.  That translates to R 23.5 for a 16" cordwood wall and R-35 for a 24" cordwood wall according to these tests.  

The full document, with pictures and mathematical explanation is available in the document Cordwood and the Code: A Building Permit Guide.  If you are interested in obtaining the full document go to http://www.daycreek.com/dc/html/dcrflatau3.stm

Zoub writes:

"an other question:
what are the difference between "Cordwood Conference Papers 2005 CD" and "Cordwood and the Code: A Building Permit Guide + CD"
i search results of manitoba test's: what is the best document for this ?" 

    Cordwood and the Code: A Building Permit Guide has the entire seven page document from Dr. Kris Dick, P Eng. on R-value (Thermal Resistance). This is the best document for the full testing report.

   It also has two University Fire Resistance Tests (U of New Brunswick and U of Manitoba),  a Blower Door Test on a 16" cordwood home,  Certified Compression Tests for cordwood mortar, Res Check software to compute your heating load and building permit passibility, Cordwood in a Seismic Three Zone, two sets of building plans and permits and a CD of the entire document to help in your own building permit application.