6x6 or 8x8 help

[yarnammurt]

I am putting together a log/ timber house. And can't make up my mind if I should use 6's or 8's for the walls. How much difference would it make on heating and cooling?  The walls will be stacked green and have rebar drove in through 5 at a time.

[bigshow]

R Value:

2.54 per inch of softwood  6": 15R  8":20R  8" would give you just under a 2x6 insulated wall R Value.
.71 per inch hardwood: seems hardly worth even bothering if energy efficiency is in question.

The logbuilder I learned from (decades of experience), said a log of with a top diameter of 6" is as small as you dare go for any thermal performance at all be it R-Value or Thermal Mass. 

[Roger Nair]

Bigshow, you overstated the R value of softwood by a factor of at least two.  Research values are found in table 4-7 in parenthesis.  12% MC are relevant for design value.

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_04.pdf

[Dave Shepard]

That's what I was thinking. I seem to remember pine being 1.3 per inch.

[BCsaw]

I think if you stick to 8x8's, you will be much happier. With any type of log construction, it is always about thermal mass. The more you have, the better off you are. I have seen part time buildings use 4x4's, not very good in terms of warmth and strength. Inspectors like 8" as a minimum in my experience.

[Tinner]

I think if you stick to 8x8's, you will be much happier. With any type of log construction, it is always about thermal mass. The more you have, the better off you are. I have seen part time buildings use 4x4's, not very good in terms of warmth and strength. Inspectors like 8" as a minimum in my experience.

+1
i have read (on the internet) 6" is ok up to the 45th.  And 8" north of that.