Recent years have seen increased use of natural ventilation, daylighting, and cooling techniques in UK buildings. This paper describes the design and operating concept of a large, naturally ventilated and illuminated city centre library for Coventry University in the UK. The novel design concept includes four lightwells acting as ventilation inlets, each of which is fed with fresh air from a plenum below the ground floor. A central lightwell and perimeter stacks draw air across each floor plate and provide air extract routes.
An historical background of fluid mechanics used in computation of natural ventilation is provided. Unresolved issues in computation of natural ventilation for thermal comfort are discussed. These issues include the influence of building porosity on wind pressure difference coefficients; wind shelter effects; indoor air flow resistance; air flow for thermal comfort and heat stress relief; air flow computation techniques; and natural ventilation in home energy rating schemes.
The on-the-ground experience of a domestic design and construct company (Ecobuild Pty Ltd, for which the author is the designer and director), is illustrated as a case study for the application of domestic natural ventilation in the temperate climate of Sydney. Factors limiting the general domestic application of natural ventilation are discussed. Requirements of a domestic ventilation system in Sydney are listed. Examples of domestic natural ventilation designed the company are illustrated. Preliminary results are discussed. The need for domestic IAQ research and standards is stressed.
Unsteady wind effects can be important in natural ventilation, but their treatment requires knowledge of instantaneous surface pressure distributions which are extremely difficult to obtain. The paper describes a theoretical investigation aimed at determining the effects of unsteadiness and, perhaps more important, the conditions for which it may be worth accounting for them in the design process. For generality the study uses nondimensional parameters. The effects of unsteadiness on both mean and instantaneous flow rates are covered.
The wind and buoyancy pressure driving forces for natural ventilation of buildings are very low, typically less than 10 Pa. Depending upon the prevailing climatic and thermal conditions, or even the location of a building on a site in relation to other surrounding buildings and landscape, the predominant pressure force incident on a purpose-provided natural ventilation opening can either be closer to the lower range of pressure differentials (< 2 Pa) or vary over a wider range of higher pressures (2 - 10 Pa).
Energy-saving improvements in the thermal properties of buildings often have an adverse effect on indoor air quality, leading to risks of structural deterioration. In these cases, the air change rate inside dwellings must be increased while ensuring that flued gas appliances continue to function correctly. The proposed ventilation system is a cross between natural draught and controlled mechanical ventilation. It activates natural ventilation of the dwelling by means of the induction principle.
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