Greetings everybody

I'm modeling a datacenter and there are few issues about which I'm wondering how to proceed.
The project consists of two building adhered to each other. The floor areas of each building separately and of both together are within the range Medium size buildings, or is to be covered by System 5.

One of the buildings is the Admin Building. There are mostly administrative spaces and few special spaces working more than 40 hours per week - security, computer and mechanical rooms. The baseline systems for this building are system 5 (one per each floor) and system 3, which is to cover the special spaces. Also there are system 9 and 10 for few heating only rooms (identically to the proposed model). Until now - OK.

The other building however is actually the Data Center (DC). In there, the admin spaces are just 4-5 small rooms. The rest are technology, el.-mech. rooms and IT data server rooms. They belong to System 3 and some of them to System 9 and 10. There is not a situation to model one system per floor, because for this building the System 5 will be only for few rooms on the second floor.

The questions are:
1. Should I make model for each building and afterwards to combine the results, or
2. Should I make one model whereby the system 5 to cover every floor of the both buildings and then the other systems - 3, 9, 10 to be on separate basis in accordance with their internal loads and schedules.
Any advice on the matter is highly appreciated.