Building Options are a Project level switch
Building Options provide switches that will make objects either visible or completely hidden from everywhere in the project. If an object is assigned to a certain Building Option and that Building Option is turned off then the object disappears everywhere in every drawing in the Project. If it is a 3D object such as a wall or symbol then it will also not appear in any 3D views. Contrast this with Layers which are a Drawing Mode level switch. If the visibility of a 3D object is being controlled by Layers then you can not hide the object in 3D by turning off the Layer.
Building Options affect all drawings in the current Project
This is the most important difference between Building Options and Layers. A Layer will only affect the drawing that contains the Layer. A building Option affects all drawings within the Project.
I will often assign all of the Ceilings in all drawings to a Ceilings Building Option and all the Roofs to a Roofs Building Option. I can then turn all of the Ceilings and all of the Roofs off for the entire Project by simply turning those two Building Options off. If I want to see the Ceilings and/or Roofs in 3D I can turn them back on again.
Note that when an object is assigned to a Building Option and that Building Option is turned off then it is as if that object does not exist. However, I have observed one exception to this rule. Even if a Ceiling is assigned to a Building Option and that option is turned off the ceiling will still affect the elevation of any Symbols that are defined to use the Ceiling for determining the Elevation of that symbol. So even if a Ceiling was assigned the Ceilings Building Option and that option were turned off a ceiling fan will still be positioned as if the ceiling was present.
Where things get a little confusing is when you have multiple Ceilings assigned to different Building Options. For example you might have a Building Option for a flat ceiling and another for a hipped ceiling. If both Building Options are turned off so that there is no ceiling visible at all then the ceiling fan will reference the lowest ceiling, even though it is turned off in Building Options.
This adds another level of complexity. Do you want to have two sets of electrical symbols? One that would be visible when using the flat ceiling and another that would be visible when using the hipped ceiling. And if you do want two different sets of electrical symbols do you want them on the same Building Option as the ceiling they reference or do you want them on their own individual Building Option. If you give the electrical symbols the same Building Option as the ceiling they reference then it is a little simpler to manage. Turn on a ceiling and the electrical symbols turn on as well. The down side is that if the ceiling is turned off so that you can view the interior from above then the electrical symbols will not be visible either. Perhaps that is what you want and if so it would make sense to have the ceiling and the electrical symbols on the same Building Option.
But if you want the electrical symbols to remain independent of the ceiling then you would need to create additional Building Options. For instance you might have Building Options for Flat Ceiling, Flat Ceiling lights, Hipped Ceiling, Hipped Ceiling Lights. This gives you more finite control at the expense of complexity.
Bill is the owner and maintainer of SoftPlanTuts.com