See also the Drawing holes and merging zones tutorialAdvanced tab on Model Options dialog.
You can simplify and speed up simulations (sometimes quite significantly) by lumping zones, walls and windows and/or eliminating unnecessary zones and elements from the model. The following options are available:
This option reduces the number of zones by merging zones having the same activity.
This option merges zones which are connected by holes drawn at surface level (not the holes used to represent the airflow path in virtual partitions). You can merge one or more zones within the same block or across multiple blocks.
See also the Drawing holes and merging zones tutorial
Tip: The recommended way to merge zones is through the Merge zones by selection option below as it gives a greater degree of control over which zone is used as the parent.
Check this option if zones are to be merged by selection using the Merge zones dialog.
When selected, this option causes all windows on a zone surface having the same area, construction, frame/dividers, shading etc to be "lumped" into a single representative opening using the window multiplier concept. In this case just one of the repeated windows is simulated and the window multiplier is used within EnergyPlus to multiply up the window heat flows so that, overall, the simulation behaves as if all of the window had been included. For models having surfaces with many similar windows this option can provide a worthwhile reduction in simulation times.
Important Note: With Calculated natural ventilation you should not use this option if you have repeated windows having same size, glazing type and shading on a surface but different Window Operation and Free Aperture data such as % Glazing opens, Opening position, Discharge coefficient and/or Operation schedule, because any differences in these natural ventilation settings are not accounted for when checking for similar windows on a surface.
You should also switch this option off if you are running simulations to generate boundary conditions for CFD or for graphical data plotting.
DesignBuilder does not allow a multiplier for windows to be used for zones with daylight lighting control or if the 3-Full interior and exterior Solar distribution option is set. This is because for daylight control or Full interior and exterior Solar distribution, EnergyPlus must know where each of the individual windows is located to properly calculate the distribution of solar and visible light transmitted.
This is currently the only 'Simplification' option switched on by default for new models.
This option causes all cracks in a zone which are facing the same direction and have similar height to be lumped into a single crack. This option applies only when the natural ventilation model option is Calculated.