Energy-Modeling Software: Is It Worth Your Time and Money?
Even the most sophisticated programs have limits.
Synopsis: In this article, senior editor Martin Holladay looks at energy-modeling software in general, then provides information on a number of the most commonly used programs. He identifies two problems with using the software: First, it takes a long time to enter all the required inputs, some of which are difficult to assess and can seem unrelated to energy use. Second, because many relevant factors can’t be modeled, the results of some programs may not be accurate enough to be useful. Moreover, energy use is driven not only by envelope design, but by occupant behavior. Still, most energy models are fairly accurate when applied to new homes. They are less so with existing homes. For builders unfamiliar with energy-modeling software, Holladay recommends trying a free program first, then purchasing a more robust program to better integrate energy modeling into the building routine.
As residential energy codes get more stringent, designers and builders can’t avoid an increasing focus on energy efficiency. So what’s a good way for designers to get a ballpark estimate of future energy bills? One way is to look at the utility bills of a comparable nearby home. In most cases, though, energy modelling software is used for energy estimates.
Some energy modelling programs can be downloaded for free, while others cost thousands of dollars. In general, you get what you pay for, but the free versions are actually pretty good. However, none of these programs, whether free or for sale, will deliver meaningful information unless the user understands the program’s limitations.
One of the most common types of energy modelling is a Manual J calculation to determine the size of heating or cooling equipment. (It’s called a Manual J calculation because it follows the Manual J method developed by the Air Conditioning Contractors…