http://www.sciencedirect.com/science/article/pii/S0306261914011076

Energy management in buildings requires optimization and it is much better to optimize the entire system than to optimize each subsystem alone. That is to say, sub-optimization could lead to misleading results as this approach ignores the "interaction effects" among the subsystems.

Hope this helps answer your question.

Professor Yehia Khalil, Yale University, USA

Fellow of the University of Oxford, UK

It would be easier then to carry out a global sensitivity analysis of the model associated to the considered physical system in order to identify the most influential parameters while observing a key output parameter of this model.

Thanks all for your usefull information. I just finished my PhD in the field of energy , buildings and renewable energy systems and thinking of working in the area of whole system modelling instead of sub-system modelling. I am going to extend my knowledge to find a research position around this area.