This paper presents an experimental study of natural ventilation induced by combined forces of thermal buoyancy and opposing wind in a single-zone building. Experiments demonstrated that for a certain range of buoyancy strength and wind speed, two different stable ventilation modes and thus flow rates exist for a fixed building geometry at given buoyancy and wind strength. In these situations, the final ventilation mode and the ventilation flow rate are dependent on the ventilation history of the building.

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

Conventional models of building occupants' environmental preferences such as thermal comfort are used to give guidelines for the average environmental conditions that will satisfy large groups of people. The research described in this paper investigates how the preferences of an individual occupant can be modeled to predict their preferred thermal and environmental conditions. A novel, Internet based questionnaire was developed to gather thermal sensation votes.

A number of single tracer gas techniques (decay, step-up, homogeneous constant emission,inlet pulse and homogeneous pulse) suitable for measuring the local mean ages of air in multizonebuildings exist, each having their advantages and drawbacks. The characteristics of thedifferent available techniques are compared from theoretical and practical points of view. Thehomogeneous pulse technique has not been experimentally validated before. This techniquerelies on pulses of tracer gas being injected into the different zones in amounts, which areproportional to the zone volumes.

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.