Diagnosing Code Compliance Differences Between HERS Software Tools

When transitioning to Ekotrope, new users will often encounter plans that meet IECC or ENERGY STAR in other HERS Rating tools, but do not meet in Ekotrope.  They may also find major discrepancies between energy bills or HERS Index scores across the two software tools.

These can be caused by any of the following three items:

1. Differences in input parameters between Ekotrope and the other software due to user input error or XML import errors.

2. Differences in the energy algorithms of Ekotrope and the other software.

3. Differences between software interpretations of standard rule-sets, or bugs in those rule-sets.

Most commonly, investigating differences in input parameters will solve the problem.  Below are some tips and tricks for your investigation:

1. Compare the compliance reports to see where there are major differences (e.g. heating, cooling, or water heating).

2. Compare full input reports.  In Ekotrope, print the "Building Summary Report".  If the other software is REM/Rate, print the "Building File Report".  Compare these, noting any differences between the two.  Often there will be extra envelope area, envelope R values, mechanical specs, etc. with one of the input files.  This is less common when the file was imported to Ekotrope using the XML import.

3. Compare IECC UA reports.  Even if you are trying to diagnose failures of the IECC Performance Path or ENERGY STAR, the IECC UA reports can provide great insight into why a plan may not be meeting code.

In the case above, Basement Walls are the major driver of UA discrepancy.  This could indicate an input error in area or R value of basement walls.  In this case, the problem was actually an improperly entered "height above grade".  You can also compare this report with the UA report from the other software tool.  Look for differences in the "As Designed" UA for each component.  Differences may indicate that the R values or areas are different between the two input files.

4. Compare the heating and cooling loads between the two software tools.  You can follow directions from this article to access and compare Ekotrope loads.

5. Compare the Reference Home Summaries.  In Ekotrope, print the "Reference Home Summary" for the code in question.  If the other software is REM/Rate, print the "Building File Report" with the proper code filter selected.  Then compare these two reports side-by-side to identify differences.  If you notice major differences in the two reference homes where the as-designed homes are identical, please contact Ekotrope support <support@ekotrope.com>.