In buildings with mechanical ventilation there are spaces with substantial pressure differences, which bring exfiltration, infiltration and transferred air between the rooms. For such buildings we have converted a multiple cell theory to a quadratic programming problem, and developed a computer programme, MCSPID for airflow identification. Today MCSPID is inpractical use to simultaneously determine flow rates for airsupply, exhaust air, transferred air, infiltration and exfiltration with a single tracer gas.
The air leakage distribution in a building is, in certain circumstances, difficult to determine. One example of this is the ceiling of the dwelling illustrated in figure 1 and 2. It is almost impossible to make the ceiling perfectly airtight; thismeans that a measurement by difference is impossible. The inclined roof is not airtight at all. A rather simple and easy technique is to perform measurements using tracer gas and pressurisation equipment at the same time.
The main air and contaminant flow paths or the spatial distribution of the age of air (or contaminant) in a room are of great interest to estimate the ventilation efficiency performance. A simple measurement method is presented, which consists to inject or more tracer gases at locations of interest and to analyze the concentration at several other locations, carefully chosen for best accuracy. Response functions can be fitted on these measurements, which are the age of the tracers or of the air or the concentration of the tracers in function of the location.
The use of computers for data acquisition and analysis in air exchange measurements with tracer gases has become state of the art for the researcher. However, for air exchange measurements in the field, reliable operation of the equipment and the proper reporting of the results are still points of concern. Here, the computer can assist the user in the correct handling of the tracer gas equipment, in dealing with unfavourable measurement conditions, and in the production of a readable report.
The performance of ventilation provision in subfloor cavities is relevant to the fields of energy efficiency, condensation risk, and air quality. Thorough programs of site measurements of ventilation rates by means of tracer gas tests are in general protracted and expensive, and it is quite clear that would be highly desirable to be able to predict ventilation rates given details of building design, ventilation provision, and d.egree of exposure.
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