Ventilation systems with heat recovery offer several advantages such as, of course, energy savings but also the possibility to add acoustic and filtration treatment. This study was to evaluate the thermal performances of such systems for residential ventilation in France. These units usually combine exhaust and supply fans, filters and a heat recovery exchanger. To test them, a special draft is being written by the CEN experts of TC 156/WG/AH7.

Until now, there is no widely accepted way to express any index for this purpose and takinginto account the large variety of possible pollutants. Things can be simplified is the aim is moreto compare different systems and strategies than to give an absolute value of quality.For the study of a pollutant source, the main important point for comparison is the pattern ofits production, whatever this pollutant is.

A systematic analysis of recently constructed dwellings in the Flemish Region has beenundertaken within the SENVIVV-project (1 995- 1998) [I]. In total 200 dwellings have beenexamined in detail. The study involved various aspects: energy related building data (thermalinsulation level, net heating demand, installed heating power, etc.), indoor climate(temperature levels in winter and summer), building airtightness, ventilation, appreciation ofthe occupants, etc. This paper focuses on the results of the airtightness measurements thatwere undertaken in 51 of the 200 investigated dwellings.

Based on the fundamental flow equations, a set of formulas is derived for air velocities, temperature differences and ventilation rates in relation to number of openings, opening areas, net heat input, building geometry, and temperature stratification. The use of the formulas is illustrated on a three-storeyed office building.

The present paper discusses issues related to the potential of natuml ventilation techniques whenapplied to urban environment and in particular to buildings located in canyons. The paperdiscusses the specific phenomena related to air flow prcmsses in urban cauyons and presentssome of the existing methods to calculate the wiad speed distribution into the canyons.Wind speed and temperature data have been collected through experiments catried out in tendifferent urban canyons presenting different characteristics, during summer 1997.

We examine natural ventilation in buildings with multiple storeys, each storey linked to acommon chimney or atrium, and ventilated using 'top-down chimneys' to draw in relativelyunpolluted air from openings located high above street level. Two significant issues relatingto ventilation design and management are addressed. First, the common stack providesconnections between every storey and, consequently, the ventilation of each storey cannot becalculated in isolation, but must be calculated simultaneously for all storeys.

Analytical solutions are derived for calculating natural ventilation flow rates in a single-zone building with two openings when no thermal mass is present. In these solutions, the independent variables are the heat source strength and wind speed, rather than given indoor air temperatures. Three air change rate parameters a, B and y are introduced to characterise respectively the thermal buoyancy force, the conduction heat loss effect, and the wind force. The wind can either assist the buoyancy force or oppose it.

Ventilation systems using variable airflow are useful in urban areas. Due to outdoor pollutionand the indoor load from pollution or thermal sources, it is important to vary the airflow. Thismust be done without disturbing the control of the total distribution. To analyse suchproblems, there is need for a design aid. This paper presents a first version of a modularsimulation program working in the IDA environment. The program is based on a set ofindividual component-models in the NMF (Neutral Model Format) language.

A humidity controlled air flow terminal device works as a humidity sensor : its openingsurface varies according to relative humidity inside a room in order to match air flow rate topollution. These components are fouling up when used during several months.In a laboratory, an air flow with a high rate of particules is fouling up five identical air devicesin a few hours. Considering a constant relative humidity, the impacts on two devices aresimilar : it seems that artificial fouling tests can be reproduced.

The Dutch organization for applied scientific research TNO in Delft developed asystem of Controlled Natural Ventilation (CNV). It is produced by the Dutchventilation fm Brake1 in Uden.