English

This paper presents a recent field measurement study undertaken in 1999 on 73 recent Frenchdwellings. The study presented the opportunity to assess the conformity and the performancesof the dwelling ventilation systems and to assess the impact of infiltration on airchange rates.The following aspects were analyzed : (1) the type of ventilation facilities in the dwellings ;(2) the defaults in the installed systems and in their operation ; and (3) the measured air flowrates, as compared to the French standard required levels.

A currently unresolved problem in building design is the paradox between increasing demandfor good thermal insulation, and the requirement for ample levels of ventilation, to maintain ahealthy indoor environment. A possible solution to this problem is a supply air ventilatedwindow. This utilises an airflow between panes to pre-heat ventilation air to the building, andto reduce thermal convection losses thus reducing the window U-Value. At the base of thewindow is a vent to the external environment, allowing air inflow.

The paper presents results from a wider study into providing displacement ventilationin urban areas by taking air into buildings from the top without the use of fans.Results from large scale experimental work are given. These results indicate thatventilation airflows can be induced using gravity chillers and heaters in conditionswhere this type of installation would otherwise fail. The paper also describes initialexperiments undertaken to see how far the same equipment can be used in heatrecovery.One test installation is modelled using a proprietary zonal model.

This paper discusses how simplified thermal and ventilation tools could be used during thefeasibility study of buildings to demonstrate the advantages of natural and low energyventilation strategies. The paper focuses on local authority library buildings in South-EastEngland and two simplified tools were used; one using a dynamic thermal simulation andventilation method and another based on the admittance method. The prediction of both toolswere compared with measured temperatures from an existing library that has a knownoverheating problem.

The heating degree-days method is widely used for calculation of the air change heating energydemand. However, different countries perceive different values for base temperatures due todifferent insulation levels and internal loads, decreased infiltration rates through tighterconstruction practices, and low temperature settings in efforts to reduce energy consumption.This has always made it difficult to make accurate comparisons for heating energy demandbetween different countries.

At sufficiently high Reynolds numbers, the discharge coefficient Cd associated with a sharplycontracting flow through a square-edged opening is, in general, taken to be constant.

The target in this study was to decrease the energy use for transportation of air (fanenergy) with a factor of three. Two real systems composed of existing componentswere constructed in a laboratory; a mechanical exhaust system and a balanced system.The flow rates through the systems were set at values according to the Dutch BuildingRegulations. This situation is called the reference situation. A number ofimprovements have been tested and studied.

This paper outlines work in progress to develop dissemination material to assist the appropriate application of solar and passive ventilation in urban buildings.

Computational Fluid Dynamics (CFD) has been used to predict the indoor environment airflow and overall ventilation effectiveness of natural or mechanical air distribution systems. This paper highlights some applications and criticism work made on CFD in order to establish an understanding of the limitations of CFD in predicting room airflow. It is concluded that though CFD is a powerful tool for simulation, the software complexities, computational power and the level of expertise that CFD codes require shape the greatest challenges to beginners in this field.

There has been a growing interest in the use of natural ventilation in buildings to supplement orreplace mechanical air supply systems. However, for buildings in busy urban areas the potentialto use natural ventilation can be limited by excessive noise entering through natural ventilationopenings such as windows and trickle ventilators. Such openings tend to have large open areasto enhance air flow while offering a very low resistance to the transmission of external urbannoise.