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.

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.

Modelling techniques were used to verify the success of a "minimal duct" ventilation system proposed for an underground carpark in a prestigious project in Singapore. The procedure to determine the various model scaling parameters, to select the appropriate fans to model the supply and exhaust fans, as well as the "dilution fans"; and to simulate the movement of air through the vehicle access ramps are presented. Measurements from the model were found to be reasonable when compared with results from numerical simulation. However, certain modifications were needed to improve the system.

Natural ventilation has been claimed as suitable for 9 out of 10 offices not severely affected by noise or pollution, claims Andrew Martin.

In the previous issue of this Newsletter, the THERMIE Programme was presented through an interview with Mr Sampaio Nunes, Director of Energy Technology at the EC's DG XVII. In order to illustrate the Programme, this issue's subject is focused on the presentation of actual projects: six new so-called Targeted Projects have indeed been approved for THERMIE support in the Building sector after the 1995 and 1996 calls, and are now getting up to speed.