By Dennis Collin
Global parameters were introduced to Revit in the 2017 release. They are project specific parameters that are not assigned to any category. They can consist of simple values, values derived from formulas, or values taken from the model using other parameters.
A global parameter can assign the same value to multiple dimensions. You can also set the position of one element by the size of another element. For example, electrical containment can be driven to consistently offset above a ceiling object. If the ceiling design alters, cable trays and conduits will respond accordingly.
Accessing and creating parameters can be achieved via the Manage tab>Global Parameters. Additional parameters can be created, modified or set to formulas as desired.
Consider a curtain wall arrangement where several curtain panel widths need to be controlled from just a few values.
The outer sections have been linked to a global parameter called Custom Grid Width 1, and the adjacent sections assigned to another parameter, Custom Grid Width 2.
These parameters can be assigned to many objects within a project, which means that should these widths need to be altered then the change only needs to be edited once within the global parameters dialogue box.
Once the values have been changed our curtain system updates to its new values as per the image below
I have done some posts on other types of Revit Parameters which may be of interest.
Part 1 – Instance and Type : https://www.cadlinecommunity.co.uk/hc/en-us/articles/360005250938-Understanding-Revit-Parameters-Part-3-Project-Parameters