As a consequence of measures required for reducing the heating energy consumption in residential buildings , there have been more and more complaints in the last few years on the appearance of mould in dwellings . In most cases, it is retrofitted or renovated old buildings which are affected [1]. Mould growth is frequently the result of a severe reduction in the natural air change rate in old buildings following the installation of airtight windows, while user habits remain the same as before.

Building regulations prevailing in France made it compulsory to use specific ventilation systems in new residential buildings since 1969. Different kind of ventilation systems (mechanically powered, temperature driven, hybrid systems,...) have been developed. This paper reviews these systems and outlines their advantages and drawbacks in single-family or multi-family buildings, with respect to architectural flexibility and comfort or safety requirements.

In order to reduce the convective flow which is the principal responsible for the high indoor 222Rn concentrations, several mitigation technics have been developed and used in many countries. Since they don't always respond as expected, there is a need of instruments helping in their design and their evaluation. This paper suggests the use of a numerical code, based on the finite difference method, for the evaluation of 222Rn mitigation strategies in dwellings, It is supposed that 222Rn transport from soil into a dwelling occurs mainly by pressure-driven air-flow.

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.

Ventilation performance of a vertical exhaust common-duct installed in a multi-story house was analysed using model experiment and computer simulation. Pressure losses at the flow junctions in the vertical common-duct were investigated using the model experiment. The pressure distributions along the vertical common-duct in three different multi-story houses of 5, 15 and 25 stories, respectively, were calculated by the computer simulation.

A new turbinemeter is developed to be used as a ventilating rate sensor in livestock buildings. Starting from a previous sensor, which we introduced in 1983, several improvements were done tobecome a low cost air flow rate sensor with an acceptable accuracy of 60 m3/h in a range from 200 to 5000 m3/h and this for pressure differences from 0 to 120 Pa. This sensor can beintegrated in the climate control equipment of livestock buildings to improve process control.

Pressure models require a good knowledge of the pressure distribution around the building and a precise description of air paths. The hydrodynamic behavior of these connections is usually reduced to an empirical power law Q = K.dP(n) with n equal to 0.5 for a turbulent flow and 1.0 for a laminar one. We present three levels of approach to improve our knowledge of the flow behavior of building components. First, we propose a new light experimental tool to determine the on site flow behavior of building elements.

The predominant route for air movements between the floors of two-storey dwellings is via the stairwell. Such air movements are of significance in the assessment of building performance: for instance, it is possible that moisture could be transferred from ground floor areas to rooms on the first floor, resulting in an increase in condensation risk in such rooms. Several domestic heating schemes have been designed such that heating appliances are provided on the ground floor only; the upper floor relying on convective airflows for heating.

With a dynamical model, the thermal behavior of a single office room is simulated. The model includes among other things the behavior of occupants, the heat production of machines and lights, the heat flux into masses, real weather data (hourly observations) and different HVAC and control systems. The computer program calculates monthly and yearly energy consumption and a statistical distribution of the room air temperature. It can also be used to investigate the time evolution of physical processes for short periods.

As part of the IEA Research Program Annex 18 "Demand Controlled Ventilation Systems" various ventilation systems were examined in a test room. During research, in addition to thermal comfort issues, removal of particles was of importance. In order to assess ventilation systems, besides using pressure - volume current graphs, the air exchange rate was frequently applied as a criterion. The air exchange rate is, however, defined only for gaseous components.