Air movement into and out of a building is caused by pressure differences created by fans, wind, and/or differences in air density. The latter factor is called the chimney or stack effect and, generally, is due to a higher temperature inside a building than outside.
Describes experimental method used and results obtained in a series of experiments to investigate characteristics of air flow through cracks in dwellings, including the straight-through, l-shaped and multi-cornered forms found in the construction of a dwelling. Aim is to supply accurate knowledge for computer simulation of ventilation effects in a room.
Points out that energy necessary to humidify air in a dwelling is usually far greater than consequent decreased sensible heat loss. Provides basic information necessary to calculate moisture deficit or surplus due to air exchange. Calculates rate of moisture addition or subtraction from air to house to maintain given humidity ratio. Determines under what circumstances humidification results in net savings of energy, describing factors affecting humidity in typical households. Concludes that net energy cost of humidification varies with each situation.
Points out that difficulty in calculating fortuitous ventilation in buildings caused by infiltration means that energy demand of a building contributed by it is scarcely ever known. Provides equations describing infiltration due to pressure differences, which in turn are caused by wind conditions, inside/ outdoor temperature differences and possible influence of mechanical ventilation systems. Describes computer program developed in Finland to calculate air infiltration. Demonstrates infiltration rates in houses.
Discusses how building ventilation is affected both by steady mean effect of air pressures and temperatures around and within the building and turbulent nature of the wind causing air diffusion through openings and cracks in the building envelope. Studies ventilation of an enclosure with a single opening subjected to turbulent impinging airstream. Derives simple theoretical models to assist understanding of physical phenomena causing air-flow through the opening. Compares these with results of experiments on a large-scale model, states need forfurther work on this problem.
Describes methods of calculating ventilation heat losses employed in several European countries. Compares them from standpoint of air change rates. Proposes calculation procedure for new Czechoslovak standard CSN 06 0210.
A survey of current methods of calculating natural ventilation and infiltration rates showed that most design recommendations are based on the results of digital analogue studies. As the natural ventilation rate calculation methods reriewed make a number of simplfying assumptions, which have not been experimentally verified, studies have been carried out, using scale model buildings in a wind tunnel, to investigate the validity of these methods. Calculated ventilation rates were found to be up to 30% higher than the model ventilation rates.
Gives series of maps and a chart used to specify performance requirements for windows in the United Kingdom in a simple way. Gives maps for the design wind pressure and exposure grades.
Reviews the main mechanisms giving rise to natural ventilation of spaces with openings to outside air on one wall only. These are temperature difference, pressure fluctuation, mean pressure difference, turbulent diffusion and the "vane" effect. Derives expressions for the magnitude of the ventilation rates caused by each of these mechanisms. Reports wind tunnel studies of the ventilation rate in a small test chamber ventilated through one opening only. Air change rates were measured using a tracer gas.
Presents simplified methods for the evaluation of the infiltration of air in industrial and public buildings. Relationships are illustrated by examples.
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