Object volume represented in calculations?

[LeightonSS55]

Hi,
I am completing a thermal comfort assessment of a university library building, particularly looking at overheating during a high occupancy event.

The building is a mix of academic books and work stations for students, with some rooms entirely just work stations and large open spaces a mix of desk space and library book shelves.

I want to know whether I need to build book shelving and racking into the component modeler and insert it into my model? Does IES take into account the reduction in room volumes when components are inserted into them (as surely this has an effect on ventilation)? Or are they just inserted for Aesthetic purposes?

Many Thanks

Leighton