What's with the Inefficient Buildings?

[Firestar97]

What's with the Buildings always showing Inefficient in their Menu?
I think it did only show one or two Times that a Building is efficient. It seems like my Area for Power Supply and Water Filtration on the Roof of my Hippo House is the most effectively maintained Area I've ever built but the Staff Room which is also on the Roof still shows Inefficient even though the Mechanic is on the Roof the whole Time

 

[Dukemon]

I guess this about the rate if the building is in use. The Staff Room for instance shows in the Building Menu efficient(green), when there at least the half of minimum kapacility in use. (2 staffmembers in the little Staff Room). Same goes to this Kitchen Building. Is someone in this Building, the menu says it is efficient.