The importance of running a load calculation is not a new concept — but the load calculations are. And even the calculations are not entirely new. They are based on older load calculation methods, which we can now compute much more quickly than when they were first devised.
Lynn Bellenger, P.E. (Pathfinder Engineers, Pittsford, NY), opened the ASHRAE seminar “Review of Load Calculations Procedure” with an overview: “How Did We Get Here.” It is probably the best way to understand and appreciate the current load calculation methods.