Vision of the problem

First of all it's good to start with a general overview on the problems related to energy needs, a share of witch is imputable to air conditioning. This is partially due to the habits of users who changed their perception of comfort, bearing less and less hot or cold rooms, or due to the increasingly urbanized and warm cities and the differents ways of building.

The graph below [1], shows the fraction of energy used between 1973 and 2003 in residential and commercial buildings. Comparing the use of different types of primary energy resource, you can see how the use of electricity increased gradually.

Certainly the diffusion of household appliances (such as dishwashers, TVs and personal computers) has an important role, but the growth of electric power usage is also due to air conditioners and in some parts of the world is still increasing. This triggered the problem, because very often we want environments that from thermal point of view are like a "sieves". On this topic, long time ago, the architect Giancarlo Allen, secretary of the National Association for bioecological architecture, wrote [2]:

"The buildings in recent decades have been the most inefficient one can imagine from the energetic point of view. It can be useful to mention here some of the most important examples of this inefficiency:

- the wild use of always lighter and "flimsy" walls caused unexpected problems of thermal bridges with loss of heat;

- The tendency to increase glass surfaces in buildings created as a symbol of modern architecture, until they turned into a sort of element of a new urban monumentality;

- The total disregard for proper exposure of the buildings to the sun led to consider less relevant the opportunity to use natural light in places to live and work. "

Sources:

1: Hirst N., Dixon R., Unander F., Gielen D., Taylor M., Cazzola P. , Malyshev T., Janssen R.. a cura di Sullivan S. e Sanford S., “Scenarios & Strategies: 2006 to 2050”, IEA/OECD, Parigi, Francia, (2007), Capitolo 6.

2: www.crsoft.it