Dangerous and counter-productive game you're playing that may end up with dead hardware. Condensation is not always immediately noticeable, and can form hidden under the CPU in the socket causing pin rot and/or fried mobos and CPUs(been there). Keeping the air moving helps by evaporating condensation quicker than it can pool up assuming the temp differential isn't too huge, which can save ya if you're 1-2* below from being off or something in your calculations but won't prevent it.
Technically, you can run a second rad INSIDE the room, and if outside temps drop below dew point you can turn on the fans on the internal rad, which will warm the coolant attempting to bring it back to room temp. That, along with pump control, would in theory allow you to stay above dew point with a few notable issues.
- Unpredictable. Outside temps can change quickly, and if temp drops quickly without you noticing to adjust the fans and pump, you will fry your rig
- Difficult. Condensation point is not always going to be the same, and can vary greatly. Not just the inside and outside temps need to be considered, but also the humidity inside your case. This would require a humidity probe inside your case, and you can then calculate current dew point using temp and humidity.
- Counter Productive. The real solution would be to insulate your board and just run it at its potential. Without a smart controller that constantly monitors and adjust for you, there is not a single safe way to run sub-ambient systems safely without insulating. Eventually you are gonna be too distracted playing a game before a cold front and end up only remembering to check by the computer crashing to a full shutdown...also been there.