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The knowledge of the air flow and air exchange in the building is critical both on the design and operation stage of the building. Infiltration of air interferes with the mechanical ventilation and determines the proper functioning of the natural ventilation system, still commonly used in the standard buildings. The building airtightness can be described by n50 parameter, however it does not specify the real air exchange in natural conditions. According to the simple procedure of the standard EN ISO 13789, factor n50 may be easily converted to the monthly averaged air change rate. However, it is difficult to accept the same value of air change rate in any month of a year, as it is often done in the certification procedures. More precise, climate dependent conversion procedures have been elaborated in USA, but they were developed for the specific local building technology and local climate conditions. This paper presents the results of the preliminary measurements conducted in a single family house in Poland, built in a heavy-weight technology. The real air exchange rate was measured in various climatic conditions by means of gas tracing method, with CO2 as the tracer gas, in order to prove a relationship between the enhanced procedure and the external conditions. Acceptable agreement between the results of the measurement and model calculations was obtained. Based on the preliminary results, the authors determined the more realistic influence of the enhanced algorithm on the ventilation energy demand. The use of the simplified model resulted in case of the analyzed object in 15% overestimation of the ventilation thermal losses.

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The authors undertook research on the proper strategy of operation of educational building with gravitational ventilation in historic city center with high concentration of particulate matter PM10 and PM 2.5. In this facility the momentary increase in carbon dioxide concentration is often very high, and at the same time health requirements regarding atmospheric aerosol should be absolutely met. That is why long-term measurements of PM concentration outside and inside, as well as carbon dioxide concentration inside were carried out. CO2 was used also as a tracer gas for measurement of air change intensity. The article presents the first results of these tests and a correlation that occurs between the external and internal concentration of particulate matter PM 10 and PM 2.5. Due to a significant filtration effect of the external building envelope and particle deposition a potential conflict between required gravitational ventilation intensity and internal air pollution with particulate matters was partially reduced.