I cant turn off a radiator, so how to best insulate it?

[Surfing USA]

Don't use spray foam, like Great Stuff! You'll never get it off, if you change your mind later.

That's why I placed a after my comment.

[ForestBird]

That's why I placed a after my comment.

Oh, stupid me. hehe

[bflonum1fan]

Just bypass that spot. A bit of pipe and some soldering skills will get it done. It's not high pressure steam. If you can do water piping you can do this.

OK my point was taken (even though obtuse), however while it is not high pressure, bypassing the radiator maight not be all that easy. First you have to bleed the system. Then assuming that it is copper pipe (may be bad assumption, since older systems use galvanized steel pipe), you can cut and splice in a new section to bypass. Soldering copper pipe requires a few tools and a map gas torch. Regular butane isn't hot enough.

However if its galvanized steel you need to cut and maybe thread a new steel/copper transition and this would require a plumber with the right tools.

So I agree just insulate the crap out of it but do not, do not use the spray stuff or you will never get it off.

Good Luck.