questions about roof/ceiling insulation

[scattermaster]

Hey guys.
Steel "carport style" building. I'm insulating and prepping walls and ceiling for my shop.
The walls are going OK. The frame is 2 1/2" square tubing.
I put R13 fiberglass behind 1/2" plywood. The builders installed the double bubble type "insulation" next to the outer skin.
Now I'm working on the ceiling. I'm planning on doing it all with pink foam and not going to do the plywood up there.
Double bubble is next to the skin. I'm putting 1/2" pink foam next to that (mounted in the purlans) and then the 2" pink foam flush with the frame tubing.
My issue is that the frame pieces are spaced way wider than 4 feet. 5ft. on average but one section is closer to 6 ft.
I have been cutting the foam to fit, but it's generating a ridiculous amount of scrap.
That 2" foam is $38/sheet.
Is there an easy way to put it up in a vertical orientation?
I thought about cutting the extra pieces needed to make the foam wide enough and gluing them together but that seems too time consuming.
Looking for ideas here.
thx,
Jim

 

[Kaizen]

You can strap it with 3/4 wood 16” on center so it bumps it out past the steel.
Also could cut groove in foam to slip the steel in if you don’t fir it out past steel.
Not sure of best method to attach fitting strips to steel though


Sent from my iPhone using Tapatalk

 

[joey1320]

Hopefully this helps.


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[K'ledgeBldr]

Hate to burst your bubble, but you are creating a “double vapor barrier”. Double vapor barriers trap moisture between the barriers which will obviously create damage down the road. On a wood structure- rot. A steel structure- rust (yes; even galvanized at drilled holes, screw penetrations, and scratches). It can also trap enough water over a period of time to collapse sheeting.

The optimal performance under the steel roofing would be 3-4” of spray foam, or 2-3” of polyiso foam panels w/radiant barrier (aluminum skin).

 

[K'ledgeBldr]

Hopefully this helps.

That video was laughable-
There were so many wrong things it should be classified as a “what not to do” video.

 

[scattermaster]

Hate to burst your bubble, but you are creating a “double vapor barrier”. Double vapor barriers trap moisture between the barriers which will obviously create damage down the road. On a wood structure- rot. A steel structure- rust (yes; even galvanized at drilled holes, screw penetrations, and scratches). It can also trap enough water over a period of time to collapse sheeting.

The optimal performance under the steel roofing would be 3-4” of spray foam, or 2-3” of polyiso foam panels w/radiant barrier (aluminum skin).

Hmmm.
Well, spay in doesn't seem to be an option since there is the bubble wrap layer already installed by the mfg. It isn't bonded to the skin. It's supported over the frame. Thus, I can't spray anything to it. Seems like the next best option is to use the solid foam stuff and support it from underneath with strips of something.
Jim

 

[K'ledgeBldr]

Seems like the next best option is to use the solid foam stuff and support it from underneath with strips of something.
Jim

Any “next best option”... No.
Either live with the bubble wrap or remove, and start over- if you want the exposed rafters. Or, put in a ceiling and blow f/glass on top and be sure the attic is vented.

 

[The Cobbler]

at $38 pr sheet, I would be inclined to get a quote on spray foam, and you should remove the bubble wrap as mentioned .