The term snow load is used in reference to the downward force on a building’s roof by the weight of accumulated snow and ice.  VersaTube structures are pre-engineered to handle more than the snow load, they also have to ensure the structure will meet the live load requirements.
The live load includes everything that can be moved in or out of a structure over the course of its life.  Calculating the live load requires knowing how the structure will be used.   The type of use is normally referred to as the “occupancy” of the structure.
As the occupancy of the structure may change over its life, reasonable assumptions are sometimes made.  If the occupancy of a structure changes to one of much heavier occupancy, then additional engineering may be necessary to meet the building code requirement for that usage.
Accurately predicting the live load that a structure may see over its lifetime is very difficult.  The International Building Code calculates the live load requirements based on experience, measurements, and probability.