Tapping into PEX in crawl space - freezing question

I live in NC where it is not uncommon to have consecutive days of sustained temperatures below freezing. The PEX tubing inside my crawl space is not insulated. So what keeps it from freezing? If I tap in an irrigation line where the main PEX line comes into the crawl space, am I going to have a problem with a freeze break somewhere between the center leg of the tee and the front half of the cutoff valve? If so, is simply wrapping those fittings with a piece of insulation enough to prevent that?

Thanks!

I'm was just on here to get my own questions asked and am not a plumber, but this is something I thought bit about and I notice that no one has given you a reply, so I figured i would pipe in (plumbing joke anyone.) It's really more about physics then plumbing anyways.

I have my tee from the water main, and then a emergency shut off valve, then by double check backflow preventer, and then my blow out valve. I realised that water would always be stuck in the backflow preventer and sense the water is not moving it definitely could freeze. I solved this by keeping all of those components deep enough that the thermal ground heat would keep them above freezing.

Now with yours I am guessing that the only reason that pex does not freeze is 1 of 3 things or a combination of all of them.
1)The water is almost always flowing
2)The pressure raises the freezing themperature
3)The house keeps the crawl space a little warmer

Now your connection would only have number 3 going for it, and sense insulation only slows down heat transfer I would be worried about it for sure. I would be worried about the uninsulated pex pipe as well but again not a plumber.

Thanks Adrian. Yes, you understand my concern. But I worked it out this weekend. I was able to tuck the tee and cutoff valve right up against the floor decking of the living space above, and it's protected from below by the insulation batt between the joists. So that should keep the still water in those fittings safe during the freezing months.