Modeling plenums in Openstudio

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Yes that's my approach too although the Add Output is a good thing to add routinely. One note, is if I have adjacency problems during the Match and an internal wall is still defined as external, they can be manually edited via the Inspector, by assigning whatever surface that mates up against the adjacent one as the Outdoors Boundary Condition, then both become internal.

I like Item #3 a lot. It is a good idea to continually run simulations as your model developed, so you aren't surprised at the 11th hour either by unexpected simulation errors or simulation run-time.

Matt, Further to your #3, how is the measure you mention different than using the Set Attributes to Selected Spaces button? It's pretty easy and handy button. However, tell me more about your measure as I'm sure you have some enhancements that I can't think of at the moment :)

@Suley - the measure simply automates the process of manually switching ideal air loads from off (default) to on which can be time consuming/tedious if your model has many zones. I'm not sure if the BCL allows the public to upload measures yet, so if you'd like a copy I can send it to you. I generally try to move from SU to OS as soon as I can so I can start running the model through EP. Also, as of OS 1.4.0 you can intersect and match geometry in OS using the "Apply Measure Now" menu feature.

Hi David,

Thank you for the detailed response. I've learned tricks of SaveAs in lieu of Save, close project and restart in tandem with the Diagnostic script. A moving target but I know better when to stop, be careful, and preserve the preceeding work (most of the time! ha). You say, "You could break the plenum into 4-5 separate plenums..., but you can also make the plenum floor and ceiling a single solid surface...as adiabatic". Do you mean draw the plenum in place, but don't do an intersect or even a match, and just straight assign the top/bottom surface to adiabatic + set construction?

"Do you mean draw the plenum in place, but don't do an intersect or even a match, and just straight assign the top/bottom surface to adiabatic + set construction?"

Yes, that is a possible approach I was suggesting. If you want suggestions on different approaches for batch setting the boundary conditions I can go into more details. With this approach while you don't have the conductive transfer across the plenum, you still have the airflow (assuming you have setup as return or supply plenum vs. just a dropped ceiling that isn't in hvac path.

Hi David, This topic is very timely as I am modeling a mixed-use development consisting of office tower (42 floors) and mall (6 floors) for LEED certification. I have already drawn the building geometry without plenums and I just learned that the HVAC designer is using plenum for the return air. I would appreciate very much if you can share suggestions on possible approaches for batch setting the boundary conditions that you mentioned. I believe this will be very helpful once I add the plenums to the spaces.

Danny, in the plugin you can use surface search to find class = OS:Surface, Type = RoofCeiling, Outside Boundary Condition = Surface. Then use the "Make Selected Surfaces Adiabatic and Add Construction" user script. Then repeat search and user script on floors, but this time will need to look for "Ground" vs. "Surface" boundary condition, as a result you will have to hand fix the first floor back to ground. Someone could modify this basement measure to work similar to the user script. https://bcl.nrel.gov/node/37854

Also, use zone multipliers where possible, vs. modeling 42 floors.

Thanks David. Yes, I used zone multipliers for floors with similar layout.