In order to quantify uncertainty in thermal building simulation stochastic modelling is applied on a building model. An application of stochastic differential equations is presented in Part I comprising a general heat balance for an arbitrary number of loads and zones in a building to determine the thermal behaviour under random conditions. Randomness in the input as well as the model coefficients is considered. Two different approaches are presented namely equations for first and second order time varying statistical moments and Monte Carlo Simulation.

This work is centered on the transient analysis of natural ventilation provided by a single side opening when only indoor-outdoor temperature differences are present (no wind). Using both simplified "engineering" models and a CFD commercial code (2D), different cases have been examined by varying indoor-outdoor temperature difference, window size, and including or not a heating appliance in the room.

The thermal dynamic behaviour of buildings is solved by different methods; one of them is based on simulation by means of thermal node models. Computed results of the internal air temperature or the surface temperature are influenced by the used method, by the model for a solved problem situation, and by input values of model elements. The influence of the particular model element can be found by means of a sensitivity analysis.

Nowadays the ventilated cooled beam is one of the most popular air-conditioning system, e.g. in Scandinavia and Central Europe. With such beams, it is possible to create high-quality indoor climate conditions, including thermal comfort and a low noise level within reasonable life-cycle costs. The beam is suitable for spaces with a high cooling requirement, low humidity load and relatively small ventilation requirement. Typically, the beams are used in offices and conference rooms.

It is well known that the introduction of tracer gas techniques to ventilation studies has provided much useful information that used to be unattainable from conventional measuring techniques. Data acquisition systems (DASs) containing analog-to-digital (ND) converters are usually used to perform the key role which is reading and saving signals to storage in digital format. In the measuring process, there are a number of components in the measuring equipment which may produce system-based noise fluctuations to the final result.

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.