The Building Air Tightness is an important parameter on ventilation systems performanceand energy losses.Yet, the total amount of leakage is as important on performances as their effective positionin the room.Some calculations have been run according to prEN 13465 from TC156 WG2 for differentbuildings (single house, dwellings and commercial buildings) varying air tightness, valueand repartition for different ventilation systems (natural, mechanical exhaust, mechanicalexhaust and supply).All these calculations have been compared focusing on ventilation losses during heatingseason in Paris.So

Dwellings airtigthness is not well known in practice, in France.When dwellings are equipped with mechanical ventilation systems (which represents about 95% of the new dwellings in France) the airtigthness can strongly influence the performance ofventilation.In the frame of the European Joule Project TIP-VENT (Towards Improved MechanicalVentilation Systems) [1], measurements of airtightness and underpressures were made onthree multifamily buildings.

Before starting to design an HVAC installation for treatment, supply and exhaust of air to and from a building the needs should be listed, transformed to requirements and their consequences analysed. Requirements lead to different amounts of airflow for their fulfilment. These needs for airflow should be calculated. The demand leading to the highest call for airflow will decide the airflow for which the equipment should be dimensioned - the dimensioning airflow.

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 estimate of actual air change rates considering atmospheric turbulence isintroduced. The starting point is the spectral description of turbulence - Kaimalspectrum was used in order to consider the height above ground. A set of syntheticwind velocity series are generated, out from a modified spectrum. The procedureconsiders an aerodynamic transfer function (a filter) where peculiar and cut-offfrequencies are determined by the general dimensions of the building and of theexternal openings, i. e., the turbulent scales of interest.

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.

This article describes a ventilation system, developed within the framework of aEuropean project supported by the JOULE III programme (NAVAIR project). Theconcept used - natural ventilation assisted by air induction combines the advantages ofnatural ventilation and the performances of mechanical ventilation.

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.

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.

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.