I knew that the PVC and SEN foam cores we use to build boats had some thermal insulation value but I didn’t think it was as good as house construction insulation foam. At the Fiberlay design conference I learned that it is almost as good as the insulation foams. For example 90 kg Airex is 0.24 BTU.in/sqft.hr.F which comes to R 4.2 per inch. Craig Riley tells me that the PET foam gets wildly even better results when in a vacuum.
Nice.