English

Ventilative cooling represents one of the heat dissipation techniques in the building design process. In this paper, we identify the driving forces of natural ventilation and their implications within the building. We focus on the various strategies to enhance the air circulation and exhibit the limits of this cooling technique. Design guidelines for architects based on existing knowledge are suggested. Finally, perspectives in terms of future research actions are exposed

Over 90% of office workers would rather be served by natural ventilation systems, so why is it not normal practice?
Many architects and consultants argue that serious technical difficulties make it impossible to implement.               

The performance of a ventilation system, particularly that which is incorporated in centralised air-conditioning system, can be evaluated in several ways. The "ventilation efficiency and ventilation effectiveness" and "air exchange efficiency" are two of the most commonly employed methods in ventilation analysis.

In order to improve the indoor air quality a change in the ventilation system is often one of the actions. The mean ventilation effectiveness or contaminant removal effectiveness is then often presented as a measure. Great care should however be taken when evaluating a system using these parameters. Measurements have shown that in displacement ventilation the mean ventilation effectiveness can fluctuate very much for the same air flow, the same cooling load, the same inlet - outlet devices and the same height of the tracer gas supply.

In France, air conditioning of offices is often required especially in areas with high noise levels and in the Mediterranean climates. Evaporative cooling systems appear able to give a cost effective solution to the growing demand for summer comfort: hence, the CSTB and Gaz de France are currently conducting a joint research on the efficiency of such systems. On the basis of a comfort criteria, this have been done by computer simulations taking into account different kinds of systems, buildings, and climatic areas.

The faults during design and installation phases are more critical with cooling systems than with normal HY AC systems: direct evaporated systems in particular require experienced engineers and mechanics. The most common fault is oversizing the systems and the design of the year-round-use system without winter conditions equipment. When the outdoor temperature is cold these systems present problems. The aim of this paper is to present the retrofitting concepts of cooling systems together with improved energy efficiency and operation of the system.