An alternative material worth looking at is corrugated plastic (also known by its trade name coroplast) which is cheap, light, an excellent insulator, and easy to work with. Many enclosure designs ...
The foldable 'Origami' Kayak is the brainchild of a USA team at Oru Kayak. The material is actually 10mm Coroplast (they call it OroPlast) - ingeniously scored and die-cut to be assembled or re-packed ...