I need to install a Vent fan through my attic and roof. I have been told I should create a trap in the vent line to collect water from condensation. Is this the best approach in our cold climate?

I see this approach a lot in Lloydminster homes. I am not sure if only one or two contractors do this or if several contractors do it. My belief is that this approach is not a good idea as the trap will work to collect moisture but it will also freeze solid and block...