Insulating and sheeting cargo trailer
 

My enclosed cargo trailer has seen better days, so I decided to beef it up a bit. It's mainly used to haul tools and toys. I just finished replacing the floors with new 3/4" ply (exterior grade, 8ply).

Now I'm on to the walls and roof. It came uninsulated, with shitty, 1/8" Luan paneling. I'd like to insulate it and sheet it with 3/8" ply (maybe 1/4" on the roof for flexibility). The vertical supports are 1-1/4" thick.

Should I fur it out and use 1-1/2 Roxul Comfort board (R6, most cost effective) or polystyrene board (1"/R5, 1.5"/R7.5)? Any suggestions on suppliers?

Thanks

Decided to use 1" Type 1 board instead. It's only R4 but a lot easier to install and about 1/4 the cost of Dow Type IV, blue boards.