Hmmm... I've had a residential fridge and freezer in my unheated garage for twenty years now. Neither has ever had a problem with keeping the contents at the appropriate temp. It's been below zero F this year already with no issues, just like virtually every previous year. They are up against the wall that joins to the house. Maybe that makes a difference.
With that said, I believe a residential fridge is intended to perform in typical household temps around 70F. I would permanently block and insulate those outside vents and run it like it's designed. In the heat of summer I've never noticed excess heat coming off our fridge in the sticks and bricks. I used to imagine how great it would be to vent the excess heat to the out doors, but now I just don't think there is enough to worry about.
