Tape for pipe insulation

Arma flex make sheet insulation and foam tape

To seal seams in foam pipe insulation, try using foil tape or heavy-duty duct tape for better strength. You can also use special insulation tape or PVC electrical tape for moisture protection.

For foam pipe wraps, look for fire-resistant foam wrap or fiberglass insulation for high heat. Mineral wool is another safe choice, and self-adhesive fire-resistant tape can help cover gaps. Always check the product labels to ensure they meet your safety and insulation needs.

Check the manufacturer's specification sheet for the insulation. This will specify the correct tape to use for sealing joints and also the applications it can be used for. For example, insulation for hot pipes is not the same as insulation for cold pipes. Different types are needed for indoor / outdoor / underground duty. And you've already discovered that they differ in fire retardancy.

I was using generic closed cell foam insulation from Screwfix, the grey stuff with a slit in it 13mm thick. I don't have room in a lot of places for much thicker. All the duct tape I have seen dries out after a few years and falls off, I can't imagine that people can actually use it to seal ducts. I'll try the arma-flex foam. Reviews say it is super sticky, and good for insulating around valves and clamps, so maybe can do both.

FWIW, the foil I tried fall off very quickly anywhere there was any tension on it, but it seemed to stay on in areas where it did stick. But that was only after a couple of years.

Haven’t used them but worth a try