A brief history is given of research into natural ventilation over the first fifty years of the Journal, from the personal perspective of the author. One of my aims is to give an indication of the contribution that the Journal has made to reporting research on this subject. Another aim is to provide a background for researchers who are starting out in research. There are nine areas of research that I have identified, namely:- steady envelope flow models; flow characteristics of openings; unsteady envelope flow models; internal air motion, zonal models and stratification; contaminant transport; age of air; CFD and its applications; scale modelling; full-scale measurements. For reasons given in the text, some of these topics are only very briefly mentioned. For example, the sections on contaminant transport and CFD are relatively brief, partly because they are the subject of other papers in this issue. (Similarly, the feasibility of natural ventilation relies on the adaptability of the occupants to be comfortable, but thermal comfort is not covered at all here, because it too is the subject of other papers.) The paper concludes with a few personal comments on the design process, since the underlying aim of research is to minimise the risks associated with naturally ventilated buildings.

The prevailing paradigm in indoor environment control of office buildings often excludes natural ventilation, due to the fact that its dynamic nature may not be compatible with the close control of mechanical conditioning systems. Due to the potential magnitudes of wind and buoyancy forces in tall buildings, the challenges are greater. This research is concerned with the prospect of purely naturally ventilated tall office buildings. The naturally available driving forces of wind and buoyancy are investigated separately or in combination. For the present study, it is proposed that "segmentation" might offer the least risky approach for envelope design of non-residential tall buildings. Two modelling approaches are adopted for investigating the segmentation effects. Firstly, the single-cell envelope flow model is evaluated under the steady state condition. Further dynamic effect with the multi-cell model is then examined using dynamic thermal simulation with an airflow network using ESP-r (ESRU, 2002). Segmented and non-segmented atrium buildings with ventilated double facades are adopted as the main building configurations in the second stage for coping with the potential magnitude of impinging wind at high levels. The overall objectives are to determine whether the magnitudes of airflow rates and the desired flow pattern through openings can be achieved over a range of specified conditions. Potential conditions where the design goals may not be ensured are identified. It is supposed that a seasonal control algorithm could be developed to provide the optimum desired flow pattern, sufficient flow rates for ventilated cooling and uniform air flow rates across floors. The control of segmentation can be achieved by the use of dampers between cavities for the naturally ventilated tall office building design in the climatic context of Taipei, Taiwan.

"Natural Ventilation of Buildings Theory Measurement and Design." International Journal of Ventilation, 10(4), pp. 405–406

This chapter contains sections titled: Introduction The Effect of Gravity on Ventilation Flows Types of Flow Encountered in Ventilation Fluid Mechanics – Other Important Concepts and Equations Steady and Unsteady Ventilation Flow Through a Sudden Expansion Dimensional Analysis Heat Transfer between Air and Envelope Definitions Relating to Ventilation Rate Errors and Uncertainties Mathematical Models Boundary Conditions Bibliography References

Wind tunnel experiments have been performed on a scale model to study unsteady natural ventilation through multiple stacks. Part 1 of the paper [1] concentrated on the characteristics of the mean flows. Part 2 concentrates on the instantaneous characteristics of the flows, both in terms of the experimental measurements and in terms of an unsteady envelope flow model.Further investigations into the experimental measurement techniques are described. These relate to improving the hot-wire calibration, to the instantaneous flow balance with multiple stacks (and the importance of model rigidity) and to the increased importance of internal air motion with the higher flow rates associated with multiple openings.The experimental measurements of stack reversal percentage are examined in some detail, regarding the effects of wind direction and Reynolds number and how the reversal percentage relates to a simple pressure parameter.Following on from Part 1, the effect of opening configuration on the instantaneous properties of the external wind pressures is investigated by examining their correlations. As with the mean values it is found that the correlations are not entirely independent of opening configuration.The experimental data is used to assess the performance of an unsteady envelope flow model, both in terms of calculating instantaneous values and mean values such as reversal percentage. The model is shown to perform well with multiple stacks. It is then used to estimate the effect of Reynolds number on the reversal percentage at model-scale and full-scale. (C) 2011 Elsevier Ltd. All rights reserved.

Wind tunnel experiments have been performed on a scale model to study unsteady natural ventilation through multiple stacks. A previously developed hot-wire technique was used to obtain both mean and instantaneous flow characteristics. The work is described in two Parts.Part 1 concentrates on the mean flows, since it is these that are usually used for design purposes. Stacks are a potential means of ensuring that the required flow pattern is obtained over a range of conditions, so that flow direction (rather than just magnitude) is an important issue. Two distinct ways in which a wind tunnel can be used for design are considered. The first is to measure surface wind pressures, from which flow directions can be inferred or calculated. The second way is to carry out direct measurements of the stack flows (magnitude and direction). Both of these ways are examined using the measured data and their advantages and disadvantages are discussed.The accuracy of the hot-wire technique was examined on the basis of the mass balance when only stacks are present. The effects of Reynolds number and wind direction on flows and pressures are presented. An investigation of the effect of opening configuration on wind pressure coefficients surprisingly revealed that in some cases the coefficients were affected. The effect of external flow on the discharge coefficients of the stacks was found to be consistent with earlier results on single stacks. There is evidence that the effect on the orifice coefficients is more important for envelope flow modeling. (C) 2011 Elsevier Ltd. All rights reserved.

This chapter contains sections titled: Introduction Requirements for Similarity Wind Alone Buoyancy Alone Wind and Buoyancy Combined Use of Water as the Modelling Fluid Relevance to Design References

This chapter contains sections titled: Introduction Concentration at a Point Conservation Equations for Bounded Spaces, Envelope Models Conservation Equations for Large Unbounded Volumes as Used in Zonal Models Analytic Relations for Concentration at a Point Analytic Relations for Uniform Concentration Analytic Relations for Non-uniform Concentration Calculations with CFD, Coarse-grid CFD and Zonal Models Definitions Relating to Contaminant Removal Relevance to Design References

This chapter gives an overview of ventilation and air quality in low-energy buildings, leading to a description of how materials can influence the performance of ventilation systems. Emphasis is placed on natural ventilation, since, in principle, it offers a passive low-energy solution. Potentially important contributions from materials relate to the control of envelope leakage, thermal storage with phase-change materials, 'smart' glazing for controlling solar gains and, possibly, porous materials for insulation and night cooling.

The well-known case of a simple naturally ventilated building with two openings, uniform internal temperature and opposing wind and buoyancy forces is re-visited. In particular, it is shown that the effect of wind turbulence can play a deciding role on whether or not multiple solutions occur. It is also argued that in practice the number of possible solutions is three rather than two.