What's the best way to model a random level of a residential build?

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Hi everyone!

I have to model a level of an residential construction. The build have about 20 floors. I would like to simulate the 10º floor to obtain the heat gain in a specifided day. The question is: which is the best way?

One possibility is to model just the two the top floors and the two bottom floors.
Anyone know's about any paper that talk's about that?

The aim of the simulation is compare the four apartaments of an floors

Thank's !