If you are an energy-modeler or work with one, you have probably wondered if all this extra work is worth the effort. When doing energy models, it seems like you spend more time and money on the model than it could ever be worth, but it only seems that way. Remember, buildings last a long time and they consume about 30% of the energy used in the United States. In other words, energy models pay dividends.

So, the first thing to establish is this: What is the purpose of energy-modeling? Most people will tell you, “It’s to save energy”, but that is over-simplified. Some people will even argue that it does not save energy since it is almost always a ton of work and in fact costs energy. These people are wrong. In the...