In the frame of a Swiss research project, a passive tracer gas technique for the determination of multizone air flow and contaminant transport in buildings was tested, based on previous work in several other countries. First emission characteristics of the three different sources (PMCP, PMCH and o-PDCH) and the adsorption characteristics of the passive samplers (standard Perkin-Elmer AD400 adsorption tubes) were established.

The Particle Streak Tracking System (PST) is a fast method to measure two- and three-dimensional velocity fields in room air flows with measuring areas up to 5 m2. The two-dimensional method works with a single pulsed white light sheet and one digital camera. For three-dimensional velocity measurements in planes a laser light sheet system using three separate laser sheets with two different wavelengths and two CCD-cameras is employed. To visualise the flow helium filled bubbles are used. A description of the set-up will be given and the data evaluation process will be explained.

The intention of this paper is not to compare discretization schemes but to show some advantages of a stabilized finite element method for modelling natural ventilation. Based on the finite element theory we present a formulation of boundary conditions that can be used for most ventilation openings in buildings. Stationary as well as transient situations can be considered without modelling of the outdoor space. Mathematical background and implementation details are discussed. Results are presented for ventilation of a living room at typical outdoor conditions.

With the purpose of evaluating validity of the application of CFO on the problems of cross-ventilation, numerical simulation was performed, using standard k- E model and two types of modified k-E models which improve evaluation accuracy in production term of turbulence energy, and also using LES, and the results were compared with those of the corresponding wind tunnel experiment. As a result, it was found that the defects of the model characteristic to the standard k- E model could be improved to a certain extent by application of the modified models.

Large eddy simulations (LES) were performed for flows relevant to or incurred in ventilation air motions with and without thermal effects. The emphasis was placed on the discussion of the possibility and potential of LES for modelling indoor air flows. Some prospective views were given on the capability and implementation of the LES approach. LES is a potential tool for providing detailed and accurate solution of turbulent flow and heat transfer in analyses of indoor environment and building energy performance.

This paper shows that under certain conditions, multiple solutions for the flow rate exist in a natural ventilation system, induced by the non-linear interaction between buoyancy and wind forces. Under certain physical simplifications, the system is governed in steady state by a non-linear algebraic equation or a system of equations. Three examples are given here: a single-zone building with two openings, a channel with two end openings, and a two-zone building with two openings in each zone. Analytical and numerical solutions are presented.

Solar energy air-collectors installed on the sun-oriented building facades can be used for improving natural ventilation of adjacent rooms. The basis of the physical process is an unbalanced buoyancy force arising from the temperature difference between ambient and the air inside the room. Although difficult to control due to the variability of the climatic conditions, these devices can be used as means of reducing the need for conventional energy to provide indoor air conditions within acceptable limits required by health and comfort considerations.

Air may be pre-cooled using thermal mass before it is supplied to an occupied space. One option is to pre-cool the air in a basement space and exhaust the air at high level through stacks. However, the thermal forces that determine the direction of airflow, including heat gains in the occupied space, thermal mass cooling and the external air temperature may counter each other, and result in flow reversal.

In many cases natural ventilation is used to ensure an acceptable indoor environment. However it is difficult to design a building for acceptable ventilation rates and indoor comfort without the proper tools or guidelines. The passive building simulation tool Building Toolbox was extended with natural ventilation models for the design of natural ventilated buildings. The simulation tool was verified with actual measurements during three case studies to ensure its integrity and to illustrate its applicability in this field.