They are looking for a system such as the other responders have indicated from Siemens, Honeywell, Johnson Controls etc... The requirements should have been outlined in a specification Division 15 Mechanical/HVAC (typically) in addition to what is on the drawings, unless the design is using the new CSI standards for specifications then there is a separate section defining what is required. Like the other responders have said, be careful, what does the "Energy Management System" do? Monitor only, supervisory control, are you using an HMI software? What are all the systems you are monitoring or controlling? HVAC, Fire Protection, Access Control, power distribution (power main, distribution, panel boards). The pieces / parts are all there to do it. You can use most HMIs with BACnet drivers and many manufacturers support the protocol. I have done a system using BACnet over ethernet with various converters to connect Citect HMI to power distribution using Lithonia products, HVAC using Alerton controllers, access control, fire protection with Simplex. We had a decent definition of what was being monitored and/or controlled for each of these systems.
Good luck