Solar shading analysis step

[shahryar+]

Dear All,
I am analyzing a multistory office building with five floors to calculate heating, cooling and lighting loads . The fifth floor
( the last floor ) is the proposed zone for doing it.

I am facing problems in calculating the solar gains for the building in Sun-Cast and it takes a long time without any result.
I would like to kindly ask you if it is correct to omit other floors except the proposed zone and calculate Apache.

Yours sincerely,
Shahryar