We have set a time limit for our sizing (10min) and energy (20min) simulation runs because models that take a very long time to finish are not very practical if user wants to explore different study options with different input parameters.
Here is the list of suggestions to consider if you are experiencing simulation time outs:
Number of zones
EnergyPlus does not have a theoretical maximum for the number of zones that it can simulate but it is always a good practice to have the least number of zones that is possible. That being said EnergyPlus should be able to finish the simulations in timely manner even if your model has less than 80 zones.
However the simulation time is not only proportional to the number of zones in the model but also to the zone's complexity (high number of envelope polygons associated with zone) and other input parameters.
If you are experiencing time outs and you think that the reason might be a high number of zones in the project combined with building envelope complexity try to do the following things:
1) Break down the building into multiple concepts.
Example for the building with total of 3 floors (ground floor plus two floors):
- Copy your starting concept two more times
- Rename the first concept to "1st floor" for your continence, second and third concept to "2nd floor" and "3rd floor"
- In each concept ignore other two floors by using "Ignored" option in the floor dropdown in the "Zoning" tab.
- Run all three simulations.
- If all three simulations are successful you can than group the concepts to get the summarized results. For more information on how to group and ungroup concepts please visit the following link
"Ignored" floor option:
You can apply the same rule if you want to break your building in to the groups of different zones
Number of windows
Number of windows in your project can have a significant impact on the speed of simulation execution. A good practice is to combine multiple windows that are in the same zone and with the same orientation.
You can try to do two things:
1) In your SketchUp model replace multiple windows that are on the same exterior wall with the one window that has the area that is equal to the sum of all induvial windows. Strip Window position on the wall will not effect the results
2) Use "window to wall" ratio in Sefaira app to simplify windows. You can replace (turn on and off) your original windows with the strip windows that are based on the percentage of the "window to wall" ratio value. You can assign the same "window to wall" ratio all orientations or you can vary "window to wall" ratio for each orientation
- In the "Envelope" tab turn on the "Override Glazing Ratio"
- Change the "window to wall" ratio for all orientations
- To change "window to wall" ration for each orientation, toggle the multicolor button
- Click on each orientation (A,B,C,D) to change the "window to wall" ratio for each of them.
In Sefaira all polygons that are not associated with the building envelope are tagged as "shading". Very often if your model has a lot of construction details, those surfaces can be interpreted as shadings objects. The easiest way to check the number of shading objects is to to go back to Sefaira plugin and check for the number of shading objects
Try to keep the number of shading objects under 50.
Simulations that include "thermal comfort" analysis are taking considerably longer time to finish than the regular simulations. Everything that has been said in this article applies even more if you are running a simulation that includes "thermal comfort"
Additional modeling guidelines
Following videos describe the best practices when it comes to how to prepare your model for the simulation in Sefaira