Hello, I am remodeling a 1970’s ranch style house and will be taking it down to 2×4 studs and plywood sheeting.  I’m in South Central Montana.  We have 2-3 months of hot dry summer and 2-3 months of cold dryer winter and otherwise pretty moderate weather. Rainfall is only 14” per year and average humidity ranges from 40 in winter and up to 60 otherwise.    I hope to do a deep energy remodel of the walls and an entirely new roofline (cold air vented metal roof.)  I will have a conditioned attic.  Site location is on top of a hill (Southern Exposure) that is often westwardly  windy.  We are always in danger of summer wildfires so I was thinking perhaps Rockwool would be a good exterior insulation and fiber-cement (everlog) siding would be good as I did lose my barn to a wildfire a few years ago and don’t wish to repeat the experience.  I on on propane and have a 95% efficient variable speed furnace but hope to put in a CERV attached to geothermal soon and only use the furnace as my supplemental heat.  That is if I get the wall and roof design right and that is where I need your advice.  I want to get this right!   We have all seen the ultimate wall design per Joe L. but for my dry location I can’t see the need for anything more than maybe a smart vapor retarder like Membrain behind the Sheetrock and maybe Tyvek (the crinkly rain screen kind) to the exterior of the insulation.  I plan on using either Cool-vent panels or making my own cood vented (think Joe l. High snow/cold weather design)   roof and repurposing my cedar siding into 1×4” rain screen spacers to put siding on. The Membrain people (at Hunter Panels) say their smart Membrain works both as a vapor control system and a weather resistant/ air barrier. Does anyone have experience with a smart membrane and care to comment?   Are these claims correct?  I am thinking (hopefully this is correct) that I really only need to worry about air control through the walls and roof and not vapor so much in my climate .  The CERV can help with whole house air/vapor as it deals with air quality and I can let my walls essentially dry to both inside and outside. If I have to I can install a dehumidifier or humidifier in this system if needed to keep house at 45-50% humidity.   Is this reasonable thinking?  If you were building this what order of materials would you use to make this hybrid “perfect wall.”  I am fully open to any and all ideas and constructive criticism if it helps me in my quest to marry building science and energy conservation tailored to this particular climate.