Since the beginning of this decade, natural ventilation in office buildings has been receiving specific interest. There are two sorts of application. Natural ventilation can be a strategy for indoor air quality control. It can also be used as night ventilation during warm or hot periods. In this case the objective is to cool down the thermal mass and improve the thermal summer comfort. The EC JOULE NatVent project wanted to identify the barriers to the application of natural ventilation in office-type buildings in moderate and cold climates and to provide solutions.

The paper describes the results of a Pan-European survey carried out on identifying thebarriers that restrict the implementation of natural or simple fan-assisted ventilation systems inthe design of new office-type buildings and in the refurbishment of existing such buildings.

This paper gives an overview of the EC NatVent (TM) project on 'Overcoming Technical Barriers to Low Energy Natural Ventilation in Office Type Buildings in Moderate and Cold Climates' which has been carried out under the European Commission Joule Programme 1994-98. The project was targeted at countries with low winter and moderate summer temperatures where summer overheating from solar and internal gain can be significantly reduced by low-energy design and good natural ventilation.

In many existing ventilation systems unintentional reentrainment of pollutant, due to improper location of exhaust and air intake, decreases quality of indoor environment. Unfortunately, the more precise method of assessment of exhaust plume behaviour, the more difficult potential application in regulatory codes and standards. The aim of the paper is to discuss advantages and disadvantages of different types of the models and their applications in regulatory requirements.

The paper presents further then an integrated model the supporting methodology that allowsto assess natural urban ventilation conditions both outside and inside constructions.Though some particular aspects arid procedures can be complex and time consuming thegeneral structure is quite simple:1. to establish wind regimes as a boundary condition - information can come from windmeasurements at undisturbed areas Like airports;2. to integrate these regimes within the site - using numerical models to transfer information tothe site;3.

From an air pollution study in a medium-sized, seaside town in Central Greece (Volos) it wasfound that some common air pollutants (CO, NO, NOx, SO,, 0,), whose emissions are connectedto activities and conditions that reveal some characteristics of periodicity on a daily,weekly or yearly basis (e.g.: production activities, meteorological conditions), are monitoredin the atmosphere in concentrations that reflect this periodicity.

To conduct a controlled trial to test the ability of a newly developed electrostatic air cleaningtechnology (EAC) to improve Indoor Air Quality (IAQ) as defined by levels of air borne particlesand to investigate the potential to reduce non-attendance rates due to illness among children intwo Swedish day care centres.

Modelling of indoor pollutant concentrations that varies in time can be a useful tool forestimation of the strength of internal sources and sinks. Usually the modelling has beencarried out using one zone, i.e. with the assumption that the air is well mixed [1,2,3]. Thepresent paper demonstrates that the methodology may be modified to fit multizone situations.By studying the decay of a tracer gas, a correct model can be obtained for a specific volume ina building.

This study describes how the air quality in a displacement ventilated classroom can beinfluenced by the position of a contaminating person, and by the activity of a person who walksaround in the room. Tracer gas measurements have been performed in a full scale mock-up of aclassroom, with person simulators at the student's desks.The spreading of contaminants from a person seems to be strongly dependent on the positionof the person. The closer the contaminating person sits to the outlet terminal(s), the less ofhishers contaminants are spread in the room.

In this paper ventilation strategies are examined in order to improve the thermal performanceof an attached sunspace of a two-storey semi-detached house in the area of Athens Greece.The ventilation strategies examined are cross and single-sided ventilation through the verticalwindows of the sunspace. Simulations were conducted implementing multizone ventilationmodel COMIS coupled with the thermal simulation model Suncode.