Contact/Construction Issue - E+

Hey all! I came across an issue that I’m not sure if it might be a mistake on my end or a possible bug on the Create EpPlenum component.

I have two zones created with Zones2Masses and the top one is a plenum, which was created with Create EpPlenum. The issue is the following: the default construction assigned for both the bottom zone floor and the plenum floor is Interior Floor. But, at the same time, the top of surface of the bottom zone was assigned as Interior Ceiling, which causes an EnergyPlus Error since the constructions are not the same (at least in this case, where in my project they differ, being that the interior floor is concrete but the interior ceiling is a different material). The bottom surface of the plenum should be an Interior Ceiling as well.
I’ve attached an image to clarify.


Create EpPlenum set the loads to 0 and doens’t change the constructions.

That is fine. They are basically the same construction with two different names. See the idf file.

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I had the same question and I’m glad that the plenum “floor” is inconsequential. However, Before I saw this I Ran a second (no plenum) office building model to see how different the EUI would be and I’m getting a number thats twice as big even though the plenum is only 25% of a story height. Does that sound right?

Having thought about this for a couple of hours, something dawned upon me. Is it possible that the plenums were registering as floor area in the EUI calculation and that replacing them with typical office building room volume not only increased the energy devoted to conditioned volume but decreased the floor area divisor…radically jacking up the EUI?

Yea, the Legacy plugins never had a good workaround for this. In the latest development version of the LBT Honeybee plugin, I just recently added the ability to discount certain Rooms from the floor area in the EUI calculation:

If you use the latest HB Plenum component to set up your plenums, then this discounting will be done automatically.

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