The more I think about it, I am considering that the metal, if sealed up, can operate just fine as an air seal. I think what I might do is simply run along all the interior seams and spray foam those before adding insulation. The screws already have to be water tight so they are not going to leak. I just need to get good seal on the bottom and top.
I am using glass because it is very easy to modify and replace later, cheaper, gives a nicer interior finish with plastic backing, and better fire resistance if done right. Not saying foam is a bad thing but I like glass for the most part.
the screws have a seals. for most part those seals do last a long time. but have had to replace some due to the rubber breaking away. and causing rain / water / air leaking in from were the rubber seal was.
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spray foam can be good / bad pending on time of year it is done. my experience with "great stuff" red can close cell spray foam you can pickup at local hardware stores. is only use it in 70 degree weather and preferably hotter.
an example i put some spray foam around a old window frame work that was bricked over years ago in the house. it was in the 40 degree weather out side. come spring time when weather was around 70 to 80F outside. i hear a loud BOOM! the gas trapped inside the little bubbles of the close spray foam expanded just enough, to put enough pressure to blow out the window (that was bricked over on the outside). i was actually surprised that some of the spray foam i initially put in was still "wet" so when it went BOOM i ended up getting wet spray foam spray over the floor and a near by wall. that i had to let dry / cure before scraping off.
lesson learned.... is make sure it is warm outside. to begin with.
i have had to remove some of the spray foam (great stuff) i have put in over the years, and on metal buildings / sheds. i notice a difference. when it was cold outside, vs warm outside when i sprayed it in. the cold outside the spray foam was easier to take off. almost like condensation formed or some sort of layer formed between the metal and foam that i sprayed. the stuff i sprayed when it was warm, i had to give a few extra tugs / pulls and once removed almost seem like it glued itself to the metal (leaving behind bits and pieces on the metal like a glue might)
other things i found cold vs warm when applying spray foam. i have seen metal being pushed out in summer. to a outside door being hard to shut in summer vs in winter.
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when i looked up spray foam a few years back... all the professional setups had some sort of "heating element" that heated things up 100 plus degrees (no clue how it is anymore).
but i would imagine having it being summer good time for spray installations. it just not initially spraying having heat up. but i would imagine a long term "warmth" in 70's or higher temps. during the initial curing and then for the FULL cure... so the little air / gas trapped in the gas bubbles. stay more uniformed and do not expand/contract as it cures / hardens all the way up.
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this old house. never had plastic wrap put on it. and tearing into some areas (windows / door seals) and remember some siding needing being replaces years back. the wrap more likely does better at were pieces of plywood or like come together that little seam / crack between the 2 pieces of plywood. is were i remember seeing damage. from simple air (moisture) coming and going through the crack.
nail / screw holes real no issue. but rather the cracks were lumber came together. and the spaces between nail / screws were something might go through (window, laundry vent, various vents up through roof).
corners being a bigger issue. due to it can be harder to get everything nice and perfect in them. ((focus during install of plywood and like is to get main wall looking all nice, and then putting a piece of trim work in a corner. end result is corners and were lumber and like meet = big cracks and gaps behind the trim piece))
most of work on the old house and the 2 sheds has been primary just above, dealing with corners (were floor and wall meet, to wall corners, to corners were ceiling and wall meats, to around windows / doors)
after above it is normally the "seams" between plywood to plywood or metal siding to metal siding for the metal sheds (both sides and ceiling) i tend to use "metal foil tape" used in HVAC and then spray foam or like. over areas were plywood to plywood cracks are along walls and ceiling. and then put spray foam over top of it. (if crack is large, i might run a small little bead of spray foam into the crack, and then foil tape over it, and then do regular insulation (make it more spray foam, hardboard insulation, rolled in fiber glass insulation) the foil tape seems to always stick better than any other tape i have found, and seems to cause the foam to expand better along and into the crack. vs not putting anything over the foam when put spray foam into the crack. ((primary goal is to stop air coming in or out))
