Primarys fermenting in freezer
 

I plan on doing some lagers in the near future and have a question about fermenting in the freezer with a controller. With the CO2 thats being emmited from the primarys, does the freezer need to be vented or does it not really matter.

It doesn't matter. The seals on a freezer aren't made to hold pressure. If you build up enough of a delta P the CO2 will just leak through the seal.

I do this with my lagers, never had issues.

I have heard of people having issues though, but mainly from yeasties that like to emit sulfur and that being a difficult odor to remove from the freezer. I've never had that issue YET, but that may be one odor to try and vent or use some baking soda if that works.

Just don't open the lid and stick you head in for a sniff. It will take you several seconds to catch your breath again.