2. Efficiency over time

Efficiency, as described in the previous paragraph, can be described as a "steady-state" concept. This corresponds to the usual contexts of industrial processes. In the case of construction, this steady state, known as the "operating phase", is much more complex, since it must take into account the behavior of users with regard to the building.

This essential interaction raises the question of how efficiency can be sustained over time in the face of the vagaries of a fluctuating environment. In common parlance, we could say that efficiency must be "robust" enough to withstand the variations of different stakeholders.

In fact, from the perspective of sustainable development, it is imperative to question the relationship between "efficiency and duration" in two ways:

• how is the display of efficiency...