What insulator is used with the Wave panel? What is its lifespan?

DualSun Wave panels can be insulated (optionally) with a 30 mm thick closed-cell polyethylene foam (a CFC- and HCFC-free product, in monoextruded and heat-bonded plates).

This material offers very good thermal performance and excellent stability over time thanks to the closed cells that make it water-repellent. Tested in extreme conditions specific to solar panels, between -40°C and +85°C and at relative humidity of up to 80%, the insulation has met all the normative criteria. 

A fixing bar is used to mount the insulator. You can see the installation in this video.

However, the Wave insulation kit is not necessary for roof-integrated installations (with systems like EASY ROOF L1 from IRFTS). The preexisting roof insulation acts as an insulator for the panels in this type of installation.