First of all, we need a wall, a window and a section through that window
When we enter the type properties of the wall, we will see that the Wrapping at Inserts property is set to both, in other words, both the required exterior and interior layers will wrap accordingly. This representation works perfectly in a plan view, but not in a section view. The most often used method to overcome this, is to simply add a Detail Item family to section views as and when required. But how can we start automate this entire process?
One method that can be used is to nest/embed a Detail Item family inside of the window family. This method is not foolproof, but will give you a good idea of what can be achieved. Upon entering the window family, we need to draw a section through the window in plan view and go to the section view.
We need to add instance parameters to our dimensions, in order to control these dimensions in our window family. All we need is the total Wall Thickness, and Layer Thickness parameters. This Detail Item family will be applicable to a cavity wall with 110mm Brick Layers and a 60mm Air Space. Test the family to make sure that all parameters are working properly.
We now add a filled region to our family framework, and use the Invisible linestyle to areas where we do not want to see any lines. Save the family.
To add the Detail Item to your window family, set the Workplane by Picking a Plane, and enter the Section 1 view.
Load the Detail Item family into your window family and place it down. Lock the Detail Item family into place.
To make the Detail Item family parametric from within the window family, we need to Associate the Detail Item family parameters to a parameter in the window family. This can be done from within the Detail Item family's instance properties.
The Detail Item will now adjust to the dimensions that was set in its family. What we need to do now, is to adjust the Detail Item family parameters to correspond with the wall layer thicknesses.
Something strange happens when we adjust the nested family's parameters though. The filled region mirrors itself around the Y-axis.
To overcome the latter, we go back into the Detail Item family, and create four visibility parameters for the filled region: DC_Bottom_45°, DC_Bottom_135°, DC_Top_45° and DC_Top_135°.
Upon reloading the Detail Item family into the window family, and back into the project, we will now be able to control the direction of the filled region at the top, and the bottom of the window family.