A new visual method is yielded by a particular application of Mollier's h,x-diagram. Point fields (temperature and humidity) lead to a significant improvement upon previous graphic methods. Flats with mechanical balanced ventilation are drier and more influenced by the exterior climate than are with shaft ventilation system ventilated flats ("Berlin ventilation"). The evaluation of the graphic representation of the experimental results in the form of curves permits rapid assessment of the experimental results.
The air change rate in existing, older blocks of flats having natural ventilation has been measured by the tracer gas method. Measurements were made in the buildings in as-found condition. The average air infiltration rate was 0.26 air changes/h (with the ventilation ducs closed), with an overall ventilation rate of 0.47 air changes/h. The average overall ventilation rate is very close to that recommended on the basis of health requirements, although values both above and below this are encountered in many flats.