One building, one system
What is required in a smart building is not to install functionally independent subsystems but subsystems that will interact with each other.
For example: The alarm system can work with the shading system and we have a clear indication whether a shutter is closed or not
Magnetic contacts of the security system can prevent the air conditioning system from operating with the windows open.
The fire detection system can affect the opening of electric shutters and the release of evacuation passages of the building
Smart cameras can prevent an intruder from collaborating with the peripheral lighting system.
Electricity measurements can recommend milder operation of electrical circuits based on the current electricity tariff.
Excess electricity can be fed to the electric vehicle and a more efficient charge can be achieved.
The energy given by the sun can turn off the function of heating water with fuel or electricity