I was reading the cold climate case studies on BuildingScience.com (thanks for the recommendation, good reading). The fairly consistent strategy is 2x6 walls with R19 batts, Tyvek, 1" rigid foam, drainage mat and wood siding. Does the mat make a difference if I am under big overhangs anyway and don't have a lot of direct exposure? Or, is it more a let the wood siding breathe thing and just good practice? I couldn't find it at HD or Lowes? Any recommendations for a good source?