After reading many forum posts on insulation, I’ve settled on a hybrid approach. I’ve got 50 ft of SM600L Thinsulate for the walls and ceiling, and am using polyiso for the floor.

My goals are to get excellent acoustic insulation and good heat insulation for the van, without compromising roof height. I’m just over 6’ tall, so have about 2” between the floor and roof ribs while wearing shoes. I want to be able to stand up straight, at least in bare feet. Since this is a first pass at the van layout, I don’t want something too difficult to remove later, so gluing down anything isn’t ideal.

Various people have put a layer of foam (minicel, polyiso) between the floor corrugations, then another layer of foam on top, but I have access to a CNC machine, so decided to model the corrugations and carve a standard 1” sheet of polyiso to match them. It’s an easy way to get back into CNC design, and might be useful for someone else. Foil-faced polyisocyanurate is inexpensive and easy to find at most lumberyards and home improvement stores, so I decided to start with that. Carving the polyiso is easy, and can be done at high speeds - I used 12000 RPM, 3 ips feed rate with a 12” end mill and that worked fine. Probably could go much faster if I needed to. Issues I discovered:

  • with a standard upcut spiral endmill, it will tear the foil facing rather than cutting it. A downcut endmill works just fine
  • I need to get better at measuring and modelling. I’m learning Fusion 360 in the process, and didn’t double-check some of my measurments after trying rectangular patterns for the first time.