I was certain I had listed this before but all a search finds is several scattered references to ResChek under a variety of other topics/questions. d*
So here we go!
From the Department of Energy ResChek website,
"The REScheck materials have been developed to simplify and clarify residential code compliance with the Model Energy Code (MEC), the International Energy Conservation Code (IECC), and state-specific codes."
There are two programs, ResChek-web that runs online and ResChek you download and run on your computer. Some states have their own peculiar rules and ResChek is not suitable in those cases. In other states like mine (NM) the use of ResChek is a part of the state building permit application process. It takes into consideration many variables including log homes and the different species of woods.
ResChek can be downloaded here (http://www.energycodes.gov/).
Good referral link, Don.
Here is link to a map showing the model codes for energy compliance (or the lack thereof). http://www.energycodes.gov/implement/state_codes/index.stm
Residential Codes
(http://www.energycodes.gov/images/us_map_colored_res.gif)
(http://www.energycodes.gov/images/us_map_res_legend.gif)