At what point do I have to worry about condensation?

[Polizei]

I'm considering going a bit of winter cooling for my watercooling loop, by sticking my radiator in my attic, which so happens to be on the other side of my bedroom wall. Here in Cleveland, OH, winters get pretty cold, but my attic typically stays above freezing, somewhere between freezing and 40F. My room is generally somewhere between 60-70F.

Would I have to worry about condensation on the tubing?

[[XC] gomeler]

When the temperature of the tubing is below the dew point in your bedroom.

[OldChap]

To see the relationship between relative humidity and dew point at various temperatures try http://www.decatur.de/javascript/dew/index.html you will need an RH meter to get a clear idea of how things are in your room but if you live by the sea (like me) or in a damp climate then as a rule of thumb even 2 degrees below ambient will start to give you problems

[K404]

The failsafe, slightly paranoid answer is "the moment you hit ambient"

If you prep for the worst, you'll be alright

[Q56_Monster]

Start worrying. It's pretty safe to say, you will have condensation issues. It would be better if you could put your whole system in your cold room, so no prep is needed.

Here's a handy dew point calculator