I used 2 in ss ribbed type nails. They are used for putting up wool siding. This FRP is very flexable stuff and usualy it is glued to a plywood wall. As it needs something behind it I used rough-cut 2 X 4 and put 2in insulation between them. This added the strength to stabilize it and gave me some insulation. By the way my brew space in underground so my walls are always cold.
We try to ferment at a constant 65-70 F for everything. We select yeast for that environment.
You probably have 4 in walls and I would guess that for your cold room 4 in of pink insulation would be good. Then add the silver sided insulation and your done. I used the 2 in sutff. You will need some kind of covering over your pink insulation so why not use this stuff. It does not look bad and you can clean it easily
This is the stuff and you need the special tape. You can see that i used fender washers and 3 in screws to attach it.
As for grain storage we use 55 gallon plastic barrels with a lid to keep the small critters out.