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August 30, 2017 by Jokūbas Vaišvila

If a building you need to model is going to have lights and HVAC, then those systems need a plenum space above the ceiling (and possibly below the floor as well). In such cases, how can you find the distance between, say, the ceiling and the slab above? As it turns out, Revit® doesn’t have Real Height parameters for Rooms and Spaces. Instead, it calculates them depending on the actual stretch but not the bounded Height. BIM Tree Manager can help find the distance you’re looking for.

QUESTION: How do you find the distance between a compound ceiling and a slab?

ANSWER: I’d suggest using special spaces to define the volume between a ceiling and slab. Here’s how to do it.

  • Lay out regular spaces in your room and a plenum space between the Ceiling and Slab:
  • Designate the upper space as a plenum:

  • Add the parameter “Plenum“ to a table:

  • Configure your tree to see only Plenum Spaces (1)
    • To do this, first choose “Selected Parameters” (2)
    • Then check the “Plenum” parameter (3)


Your BIM Tree will look like this:
, where “True” means that a space is a plenum.
  • Create a new shared parameter called “Plenum Height”

This parameter should be an “Instance.”







This parameter should be an “Instance.”













  • Select all Plenum spaces and run the “Calculate Value” function, dividing volume by area to get Height parameter:

The final result will be your needed Height between Ceiling and Slab:


After the above configuration, it doesn’t matter how you might stretch your plenum space boundaries: the distance between the two bounding elements will remain the same.



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