It appears that you have the "monitoring" end of the system (PC view), but you say nothing about what instrumentation it is monitoring or the communication system or protocols. Possibly this is the missing part of the puzzle?

You need to decide what information you want to monitor and you need field instruments (of whatever kind is appropriate) to actually measure this data and then transmit it to that SCADA master. The choice of what you monitor is yours and that then drives the choice of what sensors are required. If you also want to use the system to manage energy consumption, then you need to decide what things you can (or want to) control to cause this to happen. Possibly intelligent thermostats can be used to dynamically alter settings to influence HVAC energy use. You might also consider managing other loads such as lighting, adding occupancy sensors to detect when areas are vacant, etc. You probably should also consider some "application" programs that do some analysis or intelligently automate some of the control actions.