Heatshrink Voltage ratings?

Was working on the solar panel array on my box truck, making the hookup wires. The connectors and wiring I am using is rated at 1kV in wet environments. TUV 2PfG 1169 PV1-F standard. I was cutting and splicing the wires longer and it got me thinking what was the voltage rating on the double wall adhesive heat shrink. Much to my surprise there wasn’t a rating printed on the sleeve or the roll!

I found this document that states some materials and voltage ratings for different environments.

Looking up the material of the heat shrink I was using it looks like the “wet” environment Polyolefin, Adhesive Lined (Cross-Linked) guidelines are applicable. Which gives me ~200 V/MIL. A mil seems pretty thin for 200V!

Heat shrink is pretty tough to measure out the wall thickness (squishes) but I am getting around 25mils of thickness.

I ended up putting two tubes of heat shrink over the splices with ample overlap.

Anyone else ever have to think about voltage ratings of heat shrink? Experiences?

Also, what tools do yall typically use for shrinking heat shrink? I am looking at upgrading to this.