There are several methods by which the airtightness of a building can be measured. One method involves the use of a fan to pressurize or depressurize the building. This creates a known pressure difference across the building envelope. Thecorresponding air flow through the fan is measured and this is an indication of the airtightness of the building. This air flow rate can be expressed as the number of building air changes per hour, a useful unit when comparing buildings of different volumes. So far only simple methods have been employed to analyse this condition.

This paper describes the extension of the previously described UMIST technique for the determination of airflows between two interconnected cells to the case of three connected cells, and gives the results obtained for a series of validation experiments carried out under controlled conditions.

Air movement within enclosures, which may result from a combination of infiltration, mechanical ventilation and convective heat transfer effects, is important for considerations of thermal comfort, ventilation efficiency and energy conservation.

In the last few years energy regulations have been introduced in many Swiss Cantons. The main goal of these regulations, relative to the building envelope, is to improve the insulation value. Consequently, typical current construction for new buildings is characterized by exterior wall and roof insulation U-values under 0.5 W/m2.K and windows with triple glazing or its thermal equivalent.

Because of the wide range of parameters (wind speed and direction, temperature difference, position and characteristics of flow paths, building shape and location) which determine natural ventilation, obtaining useful design information from field measurements presents many problems. This note provides an approach for analysing the results of field measurements of single-sided ventilation. The background to the measurements and associated theoretical and laboratory studies of possible physical mechanisms for single-sided ventilation are presented fully elsewhere.

At the Norwegian Building Research Institute, Division Trondheim, we have been working on a research project involving wind pressure measurements. The main goal of the project is toget more information about the influence of wind pressure on the heat loss from timber frame walls with ventilated airspace between the wind barrier and the cladding. The project is divided into three parts: calculations, hot-box measurements and wind pressure measurements.

We are presently working on problems associated with kindergartens which, with regard to indoor climate, are quite over populated. Typically, the kindergartens are around 300 m2 inarea and 700-1,000 m3 in volume, with 60-80 children, and withnatural ventilation only. The basic air change rate is 0.2-0.4 ach. As we have shown*, users have a tremendous impact on air infiltration which, in the kindergartens, rises from the basic 0.2-0.4 to 0.7-1.5 ach when the kindergarten is in use.

While the choice of reduction of transmission losses of a building to very low values is more or less only a question of economics, minimizing ventilation to reduce the heat loss may produce a lot of problems regarding air quality and building physics. This problem has not only been experienced in a great number of buildings in Germany, but it is also a problem common to all IEA member countries.

The test house is located in the Institute's laboratory hall. This new facility (see above) will mainly be used for the study of alternative ventilation strategies in tight houses. However it will also be used for basic air infiltration research. The main reason for building thehouse indoors, is to obtain a controlled environment both with regard to the ambient temperature and the flow rate of outdoor air supplied.

In Finland, there are three main topics in the field of air infiltration research: * simulation and measurement of air-leakage rates in building components and in buildings as a whole * airtightness and indoor air quality (thermal comfort) * thermal effects of air flow in building components. Goes on todiscuss aspects of air infiltration research in Finland.