False ceiling: plenum or a layer of air in construction? (in EnergyPlus) [closed]

I want to simulate a room with false ceiling in EnergyPlus. Could you please let me know which of the following methods is correct and why?

1- To define a multilayered construction for ceiling including a layer of air equivalent to the height of the false ceiling

2- To define a plenum zone above the room (the room height reduced).

Thanks

Closed for the following reason "duplicate question" by Anna Osborne Brannon 2018-01-15 04:46:45 -0500

Please reference this question and answer: https://unmethours.com/question/4171/...

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Anna Osborne Brannon

answered 2018-01-14 16:24:36 -0500, updated 2018-01-15 04:46:20 -0500

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Thank you for your reply. In the discussion that you mentioned, there are advantages and disadvantages listed for each strategy. Why do you recommend the 2nd one?

Aryan Shahabian (2018-01-15 02:11:35 -0500) edit

2 (on your list) is the most accurate because it correctly accounts for separate air volumes and external conduction. With your #1 the air volumes might be OK as long as the ceiling void isn't a return air plenum, however you would need to be sure that your external wall areas are correct, because the area adjacent to the ceiling void should not directly conduct to the occupied space. If you were careful about this and there are no return air plenums, then #1 could be an acceptable simplification, but it is less correct.