Expert: Dan Griffin - 1/16/2009

Question
QUESTION: I'm looking for info related to the functioning properties of a standard 2x6 exterior wall, how well it would work in Alaska compared to how it would work in, lets say in Arizona?

ANSWER: David, I can only assume you're asking if there are any advantages to the 2x6 walls.

The prime gain is a thicker wall so you can get more insulation in it.  The thicker insulation gives you a larger "R" factor.  It doesn't matter what climate you are in, a larger R number translates to better thermal separation between the interior and exterior.  The advantages gained by better R can be lost if you don't use a total air infiltration approach that includes tight and minimal windows and doors with insulating glass, sealed exterior sheathing, plugged holes in the top plates, proper use of vapor barrier (the vapor barrier location is totally different between hot and cold climeates), proper eave overhangs based on lattitude.  The insulation and R factor in the attic are more important.  The thicker walls will also isolate you from exterior sounds.

The 2x6 walls will require special door and window jambs.  I personally feel the attention paid to other air infiltration issues outweigh the R advantage of the 2x6, though the increased cost of the lumber and insulation will pay back over a fairly short number of years if you plan to live in it long term.

---------- FOLLOW-UP ----------

QUESTION: Thank you very much for the info its what i was looking for, but my follow up question is. I know where the vapor barrier is located within the system in Alaska, where it is very cold, but where is it in the system in hot climates? Thanks

Answer
David, this site has some good information:
http://www.buildingscienceconsulting.com/resources/roofs/ceiling_vapor_barrier.h
make sure you go to ~Joe's Top Ten~  I think it will answer many of your questions.

YOu will need to work out the details with code enforcement in your area.