Approaches to Implement Measures¶

In the terminology used within the building energy modeling industry "measures," sometimes called energy conservation measures (ECMs) or energy efficiency measures (EEMs), are when alternative configurations of a building are considered and simulated and compared with the original building model. Measures include added wall or roof insulation, lower internal lighting power, higher efficiency heating and cooling equipment, and many others. When using EnergyPlus within a graphical user interface, that interface often provides a way to implement various measures. When not working within a graphical user interface, users have several options for implementing measures.

For a specific building input file, a copy of the input file can be made and then modified to reflect the measure. This is an easy approach initially, but since the original building model might change, it means making the change in the file that reflects the measure. When many measures are being considered, this duplicative editing can be inefficient and prone to errors. In addition, the measure cannot be easily applied to a different building energy model without again editing another set of files duplicating the original effort. Due to this, it is very common for some type of scripting to be used so that measures can be applied to the original building model and other models of other buildings reliably and quickly. Scripting in this approach means to apply some type of programming language to the task of modifying files.

EnergyPlus includes, with the installation package, two methods of implementing measures EP-Macro and the ParametricPreprocessor. EP-Macro is similar to the C language pre-processor and allows for portions of the file to be included or excluded, portions of other files to be included when desired, and for specific entries that are normally fixed values to change programmatically. EP-Macro is documented in the AuxiliaryPrograms documentation. A file with lines starting "##" or with the "imf" file extension is likely to be a file using EP-Macro commands.

The EnergyPlus ParametricPreprocessor uses special input objects in EnergyPlus to set values for any field in any other input object for a series of simple options. This is briefly described in the AuxiliaryPrograms documentation, and more details are present in the InputOutputReference under the section on "Parametric Objects." The ParametricPreprocessor approach is very straight forward, however it has limits in the flexibility that it provides. It is suitable for implementing measures related to internal loads, constructions, and simple efficiency changes but is probably not the appropriate tool for more complicated measures.

A paper that describes various other approaches to scripting was written during the 2018 ASHRAE/IBPSA-USA Building Performance Conference and SimBuild.