Fiberglass or Foam - what's better for insulating a radiator pipe?

[Seldome]

The radiator pipe in my apartment, despite being turn off, still gets hot, and it makes the apartment way too warm.

I'd like to cover it with some kind of insulation. I've seen 1/2" fiberglass wrap as well as 1/8" foam/foil wrap.

Is one more effective than the other? Is one safer than the other?

Thanks.

[Edwin Pawlowski]

Most foams will be damaged by hot pipes. Fiberglass will do the job.