Alternatively, a tiny house can be poorly insulated because it has minimal surface area.
http://www.google.com/url?sa=t&rct=j...94455598,d.cGU
Here is a PDF about solid wood walls. The comparison is to a 2x4 cavity wall with R16 insulation (which BTW is 5 1/2" thick). A 6" log wall is better, and 8" wall is more betterer. It stands to reason that a solid 3" White Southern Pine wall would beat a 2x2 wall (really 1 7/8").
Less finish work on the interior too. Use 1 1/2" tongue and groove in
box construction, planks run vertically inside and horizontally outside, or vice versa.