Trouble shooting air distribution problems in mechanically ventilated offices often has to be carriedout in limited "after hours" periods. The method of applying a pulse of tracer to the fresh air supplyhas been found to be too time consuming to map the local mean age of air over complex floor plans.In response an automated gas chromatograph has been developed to make air change efficiencymeasurements in real time using the method of homogeneous emission.

This paper presents the results from the monitoring of a low energy building, namely, the Portland Building University of Portsmouth - UK) during February and July 1997. The BMS Research Group at the University of Portsmouth has instrumented the building so that its performance can be compared with the predictions obtained at the design stage. The Building has been operational since July 1996 and the monitoring exercise commenced in January 1997. Sensors monitor air temperature, air relative humidity and slab temperature in selected areas of the building.

Perceived barriers restricting the implementation of natural or simple fan assisted ventilationsystems in the design of new office type buildings and in the refurbishment of existing suchbuildings have been identified in seven central and north European countries with moderate orcold climate: United Kingdom, Belgium, The Netherlands, Switzerland, Norway, Sweden andDenmark.The barriers were identified in an in-depth study with structured interviews based onquestionnaires among leading designers and decision makers: architects, consultant engineers,contractors, developers, owners and governme

This investigation is part of project NATVENT TM, a concerted action of nine institutions of seven European countries under the Joule-3 program. It aims to open barriers that blocks the use of natural ventilation systems in office buildings in cold and moderate climate zones. The choice to apply natural ventilation in office buildings is very arbitrary; it depends very much on the personal preference of the architect or taken for budgetary reasons, even sometimes not considered at all.

The air flow in a Passive Downdraught Evaporative Cooling (PDEC) tower has been modelled using a Computational Fluid Dynamics (CFD) code. Water is injected into dry warm air and the interaction between the water and the air is represented using a particle transport model. This models the transfer of mass, momentum and heat between the water particles and the air in addition to predicting individual particle trajectories.

Air flow through doors, windows and other large openings constitutes a major factor inbuilding ventilation. However, due to the complexity of the physical processes involved,relevant physical phenomena are not yet fully understood.The paper presents data obtained from five consecutive experiments concerning air flowthrough a large opening (door) connecting two rooms (volumes 28.3 m and 38.1 mrespectively) with different air temperatures.

Checking models of thermal behaviour or ventilation of a room can be performed in specialtest cells. At EMPA a ventilation test chamber with several experimental facilities has beendesigned and built. The inside wall surface temperatures of the chamber can be controlledusing a software model which simulates the thermal behaviour of a real wall. As a test case aheated office room was calculated with TRNSYS and compared with measurements made inthe chamber.As an example of checking ventilation models the validation of a CFD-model of ahorizontally pivoted window is presented.

The results presented here supply values for the room ventilation efficiency of a number of configurations covering as many as possible of the ventilation systems encountered in actual practice. The study is based on experimental results and numerical simulation. Using a few configurations experimented-on, simulations were performed using CFD code, which in particular allowed the reliability of calculations to be checked. The simulation tool was then used in such a way as to arrive at results that could be applied in practice.

Concentrations of indoor air contaminants are normally calculated by assuming that they fullyfollow airflow paths in a room. This assumption is also used to predict the local residence timeof contaminants in a room, which may further be used to characterise the ventilation effectiveness.In this paper, a different methodology has been adopted, in which indoor airborne particles do notalways follow the main airstream induced by the ventilation system. Dispersion of particles ispredicted by a drift-flux model.

Existing infiltration and exfiltration calculation methods are mainly based on the stationaryapproach, where long term mean values are used for wind input data. The real wind speed is,however, varying continuously with time. Because the process of the crack flow is non-linear,using mean wind speed values will give erroneous results for the air flows.