The farm owner said nothing about it not freezing in the barn. He just said it did not get below zero. Exactly what he said to me was this: "Oh, it never gets cold in that barn. It never gets below zero". As far as I am concerned, anything below freezing is cold, never mind below zero. But then I am a wuss originally from California. I now live in southwestern Missouri and we occasionally get a few days below zero. However, unlike that farm owner in Minnesota, to me that's cold!!
It would not take much to keep a barn above zero, if the walls are thick enough, hay mow is filled and even a minor heat source like a couple goats.
Also keep in mind old Minnesota Farmers might over state things a tad, they never are 100% accurate and literal like me.
If it was a barn that was partially dug into a hill or something I would think it could be above Zero Most the time.
Sorry, I was thinking above freezing and not zero..