1. Definitions

There are many energy functions in a building, and from the point of view of their consumption, it's useful to classify them into two categories.

The general functions that account for 80% of consumption (heating, air conditioning, lighting and domestic hot water production) in general are :

• high energy consumers;

• usually found in most buildings (except for air conditioning, which is not required in France).

Specific or auxiliary functions (ventilation, mechanical energy and cooking, refrigeration, use of professional or domestic electronic equipment, etc.) are generally :

• are moderately energy-intensive, except in special cases, but are nevertheless growing fast;

• specific...