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Flukie I understand the cost variable, but I read the latter part and its almost like saying I know I should space my roof truss at 2 OC but that's to expansive so I going to space them at 4 OC use 3/4 ply instead of 5/8. See it just doesn't quite get it. That's what I feel is happening here. The right way is just that and why risk it otherwise?
Kraft face in my area IS considered a vapor barrier Pa. It says vapor retarder on the kraft faced because the Kraft Faced in the colder states needs a heavy barrier 6ml to completely 100% keep the moisture out because of the very cold areas and you are borderline in Chicago. Actually I have some questioners on the sane subject and the Big Box stores don't even Sell kraft faced insul. Just to let you know what your are doing in your set up there is what I as a builder usually end up tearing out here. Just 5% of moisture in fiberglass insul will make it loose 95% of its Insul properties! So now what.
You are reading " Mold resistance" and taking that like it's a protection. It simply means it may get mold on after the back of your studs does. So do we need now "mold resistance" studs. That's exposed in the 1 1/2 back side?
See the main objective is NOT to let moisture in to begin with.
It remains me of the saying" Its hard to remind yourself while in the swamp up to your butt in alligators the main directive was to drain the swamp and no alligators"
So now you state keep the 1/2 air gap which vents to know where and you want that in case it gets moisture behind that without you knowing it. So it will happen eventually and how will you know that? And when that does happen and to see it you have to rip out the drywall to get to it.
The plate area above needs to be sprayed foamed
The warm air theory you have to get behind the wall is EXACTLY why it will condensate You NEVER want a warm air mass to a could air mass reacting like ice in a glass in summer. That transition needs to take place SLOWLY and then the condensation's is stopped.
Basic science shows this with Dew on grass and the rain because the warm to hot was to direct. Think 95% humidity and no rain until a small cold air mass comes in.
It will be raining behind the 1/2 inch air gap without a doubt especially in the cold area you are in. Sorry Flukie I'm not trying to bust your chops here but if you would see my rehabs tear outs in basement you would want to run to get foam insul.
Here's some more info on it. YouTube - Best way to insulate a basement 800x600 YouTube - Install Rigid Foam Insulation in Basement Video Signed 21 Boat
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