I found it
I found it
International building code - this is a group U and therefore an exception. Group U includes private construction.
1006.1 Illumination required.
The means of egress, including the exit discharge, shall be illuminated at all times the building space served by the means of egress is occupied.
Exceptions:
1. Occupancies in Group U.
Pole barn construction - it has sides - if you Google pole barn construction and look at the pictures it describes it pretty well. It is just a type of building. Doesn't have to be used as a barn.