I've been in the trade all my life and the "regulations" are a complete joke. Many safety and building regulations regarding insulation have been completely reversed at some point, with some finally reverting to their original form.

It is a shambles. Trial and error seems to be the most important phrase in the rule book.
In fairness the problems concerning the properties of new materials and the fact that our climate is altering dramatically has an effect on relatively untried materials like plastics and expanded insulation.