Monday, January 24, 2011

Revit MEP–Plenum Spaces and Ceilings

I’ve noticed that Spaces and Ceilings can affect Revit MEP’s ability to display the Space element. I’ve seen it happen and then later correct itself magically. Not likely that it is magical, more like something was adjusted that changes the conditions in the first place. I admit I don’t know yet what that “magic” is.

The conditions for this to occur begin with the addition of a new Level to manage plenum areas in the building. When this new level is added and a view is created it’s a good idea to adjust the view range so it matches the available distance between boundaries. Initially it would be easy to expect this to be the reason that a Space doesn’t show up. When we add a space this error message will usually pop up.

RME Spaces Ceilings01
Changing the elevation of the ceiling or the level or some combination will result in Revit being able to show them again. I created a VIDEO that DESCRIBES how the ceiling elevation and the space properties conflict with one another.

[Addendum: January 25,2011]
The issue described above has to do with the Room Computation Height of the Plenum Level, which is a Level Type parameter. The typical Level Types in Revit Templates set the Room Computation Height to be “Automatic”. This really means that the default is 4’ from the Level unless Revit encounters objects in/at the 4’ level. If Revit find issues, it adjusts the Room Computation Height to the Level plane instead.

In this case, the Level type (used for all the levels) uses the Automatic setting, so Revit defaults (when dealing with the Plenum Level) to the Ceiling Level to find the Space extents when it encounters the slab at the 4' elevation. When the bottom edge of the Ceiling Element gets nudged to align with the Ceiling Level, Revit can no longer find a closed circuit.

The solution here, and one that can be generally used, is to create a new Level Type to use for Plenum Levels, and explicitly set the Room Calculation Height to something like 0’ 6”, so the Space will always be cut inside of the Plenum Space.

Thanks to Kyle Bernhardt for the explanation!


Anonymous said...

Amazing, thank you for posting Kyle's explanation! I've been having problems with this for a long time.

Alfredo Medina said...

When we use the mechanical template, and we select a level, we can change the type of level to be "plenum", which seems to be especially created for this purpose. However, when I change a level to "plenum" I don't see any difference in the computational height or other settings. i wonder what is different in this type of level in relation to the default level types.

Steve said...

The setting used to be a Type parameter, levels now show it as a Instance parameter so there doesn't appear to any difference between levels now. It was more important to use the Plenum "type" before. I don't think it matters now other than to be clear that one is meant for something else.

Alfredo Medina said...

Actually, "plenum" is not a parameter. It is the name of another type within the level family.

So, we can say that this type of elevation does not have any other special settings other than its name. I was expecting this type of level to come pre-set with different values, but even the "Building Story" parameter is set to Yes, when it should be No. Anyway, I think it comes with default values, and it is up to the user to modify it.

Alfredo Medina said...

oh, you were referring to Computational Height, being a parameter. Correct. My mistake.

Alfredo Medina said...

I think I understand the reason for having a separate "plenum" type of level. I think it is simply to have a level type where we can have a different computational height, especially for creating the plenum spaces, without affecting other existing level types