Michaels has provided energy simulations since the time when computers that ran them filled rooms and had less computing power than a modern wristwatch. Project setup was time consuming, and computing time was expensive! One had to know exactly how the computer model  the systems being modeled worked or the effort would be a complete failure.

Fast forward 25 years: only the interface has changed. While simulations run on speedy laptops in a matter of seconds, the underlying calculation engine (code) is essentially the same. Graphical user interfaces make it easy for anyone to use, but this can be dangerous!

In modern times, the ability to accurately perform energy simulations has been called an "art". Not really. There is an awful lot of engineering fundamentals, experience and system expertise behind a good simulation. Michaels compiled this expertise out of necessity, when "green" was just a color, for real buildings running real systems.