I think you misunderstood. There's this urban myth that opening the fridge door is a problem because it let's the cold air out. The author of this article fal

I think you misunderstood. There's this urban myth that opening the fridge door is a problem because it let's the cold air out. The author of this article falls for that one as well. When you open the fridge door a small amount of cold air is replaced by a small amount of room air. Yet, even if it was open long enough for all of the cold air to be replaced (use a fan to push room air into it) it would have zero effect. In a nicely filled fridge the mass of items cooled to the set temperature has, by means of it's heat capacity and the mechanism involved in heat transfer from solid to gas, a thermal inertia that results in negligible effects from occasional door openings. For example, I'd be surprised if opening the door to a well-stocked fridge and leaving it open for five minutes caused a 1 gallon jug of milk to drop in temperature even as much as 0.1 degrees at the core.