Hello building world,  Long time leacher of information from here, enough to make my head explode. First thanks for the entire community has offered so far.  My wife and I are building our forever home in Northern California, climate zone 3B. Seismic category D1. Wind category 95mph. Windland urban interface area (meaning high fire area, the lot was actually a fire burn lot). Now that the technical data is out of the way, we have gone with modified advanced framing for our wall assembly. Our builder agreed with 2×6″ with 24″ oc but still wanted to do double top plates…

Thank you for the opportunity to benefit from the GBA community’s experience. The following design approach using two air barriers is influenced by Martin Holladay’s Q&A comment in his 2010 GBA article “One Air Barrier or Two” wherein he stated “In theory, if you have one good air barrier, you have stopped all air movement.  In most cases the second air barrier is unnecessary. The exception would be a wall without exterior foam insulation that is insulated between the studs with fiberglass batts.”   The subject residential rehab is in climate zone 5A, built in the early 2000s with 2×6 studs…

4B, 2-story home with an unconditioned attic and 2 different HVAC systems (1st and 2nd floor) I’ve been improving the insulation in the attic (I now have R-60 with cellulose instead of R30 of fibreglass), I also air sealed the attic floor, as well as HVAC ducts with CCSF (2 inches), I’m happy to report that my HVAC runtimes during the hottest months are 40% less than the last 3 years. (Checked the historical averages from my tstat). However, I have another issue that I am trying to solve: Fresh Air / Exhaust ventilation. (Co2 levels are elevated now, possibly…