Air exchange rates in occupied buildings are difficult to assess due to their dependence on a multitude of climatic parameters and inhabitant behaviour. Moreover, the assessment of the influence of the air exchange rate on the radon progeny concentration is hampered by the diurnal and seasonal fluctuations of the indoor radon levels.

This text contains comments to the poster presented at the 9th AlVC Conference in Gent, Belgium. The project under consideration in the poster (Climatological Data Transfer) is one of the numerous research fields of the Swiss ERL program (Energierelevante Luftströmungen in Gebaüde - Energy Relevant Air Flow in Buildings).

To avoid the shortcomings and problems that occur in today's ventilation systems a ventilation concept for future dwelling-houses is under development. The concept responds to the way of living and building in the future. The real living functions are chosen to design principles, that's why the system has to be capable of operating at varying air flow rates. The building in the future is based on a hierarcical modulated system, from which, with a small set of standard components can be assembled versatile alternatives.

Mechanical ventilation systems have been adopted in airtight energy- efficient houses in Canada to provide fresh air, remove moisture and indoor pollutants and provide a comfortable environment for the home-occupants. Homes constructed under the R-2000 Home Program are equipped with mechanical ventilation with heat recovery. Since 1984, the performance of approximately 700 R-2000 Homes has been monitored on an annual basis. This monitoring has included the measurement of indoor levels of formaldehyde and the documentation of ventilation system operation.

Infiltration heat losses due to heating appliances located within the living space are normally evaluated by reducing the conversion efficiency of the boiler, with no consideration for the fluid dynamic interaction between boiler, chimney and building. Purpose of this work is to develop a simplified mathematical model of the overall (building + boiler + chimney) system, suitable to calculate the pressure distribution and air flow rate in the building induced by the simultaneous effect of natural forces and the exhaust system.

Air leakage through the building envelope is of great importance for the energy use of a building. However, from an indoor air quality standpoint, the size of interior leaks in e.g. multifamily buildings could be important as e.g. a source of pollution. Using the standardised Fan Pressurization test method, it is not possible to separate interior leaks from leaks in the building envelope. One way to separate these leaks is to simultaneously depressurise (or pressurise) adjacent apartments to the same pressure and thereby eliminating interior leakage.

The specific value of different flows resulting from air exchanges between rooms or with the outside is not always important. An extensive model is not suitable when only estimations or tendencies have to be drawn (very time consuming). So we developed a simplified infiltration model for predicting airflows in single rooms and between different zones of a building. We integrated this model into a building transient thermal simulation program set up to a micro-computer system. So as to obtain this model, we used simplified assumptions.

This paper describes a two-dimensional numerical study, by finite-volume method of buoyancy-driven flow in a half-scale model of a stairwell. The stairwell forms a closed system within which the circulation of air is maintained by the supply of heat in the lower floor. The heat loss takes place from the stairwell walls. The mathematical model consists of the governing equations of mass, energy, momentum and those of the k - E model of turbulence. The predicted flow pattern and the velocity in the stairway are presented and compared with the authors' experimental data.

An element-assembly formulation of multi-zone contaminant dispersal analysis theory is described. In this approach a flow system is idealized as an assemblage of mass transport elements that model specific instances of contaminant mass transport in the flow system. Equations governing the mass transport phenomena modeled by each element are expressed in terms of contaminant concentration variables, the nodal concentration variables, that approximate the contaminant concentration at discrete points, the system nodes, in the flow system.

Since thermal comfort on human body is influenced by the local air flow speed, it is needed to estimate the distribution of air flow speed in a room for the "effective ventilation". Numerical solution of the equations for the motion of 3-dimensional turbulent air flow and model experiments are conducted for this purpose. The experiment model is a single room model house with 2 windows on the opposite walls. It is actually ventilated by the natural wind. Non-directivity thermistor anemometers are used to measured the 3-dimensional distribution of indoor air flow speed.