This section describes the operations involved in creating surface openings and sub-surfaces. To create openings and sub-surfaces in a zone surface, you first need to go to the surface that you want to modify. You can do this from the zone level either by clicking on the navigator entry or double-clicking on the zone surface in the 'Edit' screen, if you're at the zone level.
Either of these operations will take you to the surface:
Note: When navigating to surfaces from zone level by clicking on them with the mouse, to access the "backward-facing" surfaces (i.e. surfaces whose inside face is shown) you must hold the Shift key down while clicking.
When working with surfaces, switching to Normal view rotation can be helpful in orientating openings and sub-surfaces:
You can draw, move, clone (copy), rotate and delete the following types of opening:
Note that custom openings that have been drawn by hand or copied are displayed in bright colours to differentiate them from (grey) default openings:
Note: All openings and sub-surfaces in adiabatic surfaces are ignored in EnergyPlus simulations
See also the Drawing windows and doors tutorial
Surface Polygons Generated for EnergyPlus - Technical Description
EnergyPlus requires all surfaces to be convex and it does not support surfaces with holes. But of course real-world buildings can have surfaces of any shape. So when DesignBuilder encounters a concave surface or a surface with one or more holes (not openings, but an actual hard geometric hole) it must break the DesignBuilder surface down in to 2 or more polygons. The purpose of this technical description is to explain how that is done. With an understanding of the process applied users may be able to find ways to configure their model geometry to minimise the number of polygons DesignBuilder needs to generate to meet EnergyPlus' requirements.
In order to ensure that valid polygons are provided to EnergyPlus, DesignBuilder follows the process below for concave surfaces with windows:
Inflates windows to account for any frames specified and to provide a 1mm margin around the window.
Uses the inflated window size to create a parent surface for each window. A similar process is used for other opening types except that doors, vents, sub-surfaces etc do not have frames, so that part of the inflation is not required.
Further sub-divides the surface into convex polygons to ensure that all surfaces provided to EnergyPlus are valid.
The screenshot below illustrates an example case of a concave roof surface with many windows:
DesignBuilder breaks this surface/opening configuration down into EnergyPlus polygons as shown below:
Note the rectangular polygons around each window.