Pex in crawlspace to radiator

Hi, I want to install a 2nd radiator in my mom's kitchen,
and I was hoping to run some pex under the floor, in the crawlspace.

I just realized though, that if I use that pex-aluminum-pex stuff the aluminum part would probably burst/tear if it froze. (I'm hoping it will never freeze, and of course will insulate it, but you never know.)

Is there some sort of pex I can use with a boiler in a possibly freezing environment?

Thanks,

Drippy

Any heat rated pex is fine and will preform better than copper as far as freezing is concerned. I use Uponor He-pex