Zur Normung für die Bestimmung der Luftdurchlässigkeit: Anwendung und Auswertung von Blower Door-Messungen

Blower Door measurement: in spite of standardization a lot of uncertainties

Meanwhile it is common knowledge that air tightness of a building envelope is a quality factor providing several advantages. Measurement, assessment and comparison of air permeability characteristics of buildings is far from being simple: on the one hand a variety of nationally defined non-compatible air permeability indices exist, on the other hand detailed regulations or instructions on the preparation of a building before measurement are missing in actual standards. For instance, the measuring zone is often not clearly defined, and the various options of tightening a mechanical ventilation system also yield large deviations in the results. Also the date of measurement has a substantial influence: a measurement with leakage detection in the construction phase is useful and desired for improvement. But it is not valid for approval since the building will be changed until completion.

For those reasons questions arise about the value of the air permeability determination. In addition, regarding recent low energy labelling schemes demanding very low permeability rates for heat saving reasons, it is known nowadays that only a poor relation exists between the air exchange rate n50 and the actual ventilation heat loss of an occupied low energy building. Proposals for standardised procedures with regard to building preparation and data evaluation are being discussed these days. Objectives are to find simple, pragmatic solutions for the main problems and to make known more clearly the chances and limitations of the complex assessment method.