Vent needed for fermentation chamber?

I am looking at converting a standup freezer to a fermentation chamber, I was concerned about pressure building in the freezer as the fermentation took off. Obviously there will be a small crack in the door seal for the temperature controller wire. Is there any other modification I need to do to vent fermentation CO2 or is there simply not enough produced during fermentation to even be a concern?

Right now my materials of construction are:
1) Freezer
2) temperature controller

I'm assuming it's easy as that to get anywhere from mid 60s down to the lagering temps... Correct?

 

If the pressure built up to large levels it would probably just push the door open. Can't imagine it happening though.

 

I use an old refrigerator as my fermentation chamber and have no vents on it. I have had 3 carboys fermenting in it at the same time with no pressure issues. I think you should be fine.