On Thursday, February 19, 2015 at 11:47:28 PM UTC+13, wrote:
On Wednesday, February 18, 2015 at 9:18:19 PM UTC-5, Jonathan St. Cloud wrote:
Last two trailers I got the fiberglass and had a local craftsman insulate the interior.

What did you use for the insulation?

Styrofoam sheets are probably the only reasonable answer. If you want to make it more durable you can brush or roll or spray on a layer of epoxy resin or urethane. NOT polyester resin. And some thin glass mat if you want to be super fancy.