foam insulation question - Model Railroader Magazine

Thanks, Ratled & Pops, for all yr help!

It is the pink stuff:

And on Byron's website he says either one works.
It's just that the product info says it has a "weather barrier" or something.
I didn't know if I just ignore that and carve / lay cork or what.

Carpenter's glue sounds good to me.
I can be a little patient (especially with a big doctor )

I was thinking of starting a modular n-scale railroad club at the high school I teach at, with 2x4 modules, so I thought the 2" foam on top (a la "beer line") would be a good way to go so people could scoop out scenery.

But if getting foam is super difficult, then I can work other ways.

No way I'm going to complain about the unavailability of foam insulation!  The cause of it (fab california weather) is something I can definately live with!

Thanks!
--Mark