Cross-ventilation is a mechanism using the pressure difference between the outdoor environment and indoor space to provide an energy-saving method for ventilation design. Since the ventilating flow in the vicinity of the opening is highly turbulent and unsteady, the ideal numerical method to resolve the structure of the ventilating flow is by using a time-dependent approach such as large eddy simulation (LES). However, LES requires large computing resources and there are also some uncertainties associated with the discretisation of time scales and length scales of turbulence.

Knowledge of ventilation rates in dairy buildings is essential for determining indoor air quality and for estimating green house gases and particle emissions. Two new methods for estimating ventilation rates are introduced for situations where air velocities at ventilation inlets and outlets are tedious or impossible to measure. The first method is applicable to buildings whose ventilation can be stopped or closed totally.

Five fire scenarios have been simulated with the CFD model Fire Dynamics Simulator (FDS) to analyse the performance-based fire safety design of a 2935 m-long railway tunnel. The influence of tunnel longitudinal ventilation fan activation time, fire size and the type of burning materials on tunnel tenability was investigated based on variations of two primary scenarios: Scenario #1 assumed a 15 MW fire at the front end of a train, and Scenario #2 assumed a 15 MW fire at the rear of a train.

In this work, the cooling performance of night ventilation systems and different earth heat exchangetechnologies were experimentally analysed in three office buildings in Southern Germany. One of the firstpassive energy standard office buildings in Europe was extensively monitored over a three year period toanalyse the summer performance of a highly insulated and well shaded building in which night coolingventilation was based on stack effect and cross ventilation.

This paper presents an evaluation of the local thermal discomfort level in a classroom equipped with cross ventilation, for a typical moderate summer day in Portugal. Three different ventilation configurations based on window and door opening were considered. In each, the thermal comfort, air quality and acoustical comfort conditions were also evaluated. This experimental study was made in the South of Portugal, exposed to a Mediterranean climate.

Ventilation, cooling and air-conditioning contribute significantly to the energy consumption of many existing office buildings, particularly when primary energy factors are taken into account. Lean building concepts however can diminish this energy consumption by natural ventilation and passive cooling strategies. Compared to fully air-conditioned buildings the resulting indoor temperatures float in a broader band during summer and might exceed the boundaries for thermal comfort for short periods.

Conventional methods of multi-zone airflow analysis ignore mechanical energy conservation in forming the system equations governing building airflows. As a result, airflows computed using these methods generally violate this fundamental conservation principal and thereby falsely create or destroy kinetic energy within building zones. While the impact of this fundamental oversight has yet to be fully evaluated, it need not be tacitly accepted.

The capability of HVAC systems is of interest when contracting specific function criteria such as room temperature. The probability of maintaining the criteria reflects the risk the building contractor will take when giving guarantees. The level of knowledge and use of probability in the HVAC sector is low since there are just a few tests in this area. These facts make it difficult for all actors (and especially the building contractor) to increase guarantees and develop new types of performance-oriented contracts.

In order to provide comfort in a low energy consumption building, it is preferable to use natural ventilation rather than HVAC systems. To achieve this, engineers need tools that predict the heat and mass transfer between the building's interior and exterior. This paper presents a method implemented in some building software, and the results are compared to CFD. The results show that the knowledge model is not sufficiently well described to identify all the physical phenomena and the relationships between them.

This paper describes a concept of probability-based design and its application in the field of ventilation. The path of probability-based design is followed with the help of examples concerning the air change rate caused by natural and mechanical forces. The object of this study is a low-rise building situated in two different climatic zones. Evaluation of the probability of failure gives a background for probabilistic design.