AIVC - Air Infiltration and Ventilation Centre

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air change rate

An examination of radioisotope techniques for the measurement of ventilation rate.

Examines the use of radioisotope tracers to measure ventilation rates of simple and multiple enclosures. Discusses accuracy of the methods in relation to results obtained in an experimental room with controlled ventilation. Describes an instrument which measures ventilation rates directly, following release of aradioisotope tracer. Demonstrates its accuracy and operating advantages.

Well insulated airtight buildings.

Discusses reasons for making buildings air-tight and the requirements of the swedish building code. Gives examples of design solutions for detached houses and construction details for applying an internal vapour barrier consisting of a polythene sheet. Describes application to seven bungalows, resulting in air change per hour of 0.67 to 0.86. Subsequent measurements of ventilation and air velocity showed that in mechanically ventilated airtight houses the flow of ventilation air can be accurately controlled by the exhaust fan.

A method for the assessment of the wind induced natural ventilation forces acting on low rise building arrays.

Reviews existing methods for the prediction of infiltration rates and the factors influencing the pressure difference across buildings. Describes experimental procedure used in tests conducted in wind tunnel. Discusses results and presents prediction technique which enables surface pressures acting on aparticular building situated within an array of similar low rise buildings to be estimated, procedure takes account of the geometrical form of the building spacing parameters describing the array, direction of the wind and the upstream fetch conditions.

Use of a portable gas chromatograph and tracer gas for rapid determination of air ventilation rates

Describes method of measuring the air-change rates using sulphur hexafluoride as a tracer gas. The system comprises a highly portable gas chromatograph with an electron capture detector. The system will detect tracer gas without interference from other materials which may be present. The technique takes about six minutes to determine the ventilation rate. Gives practical examples and suggest extensions of the technique for carrying out cross air movements, for example in a hospital.

An intercomparison of tracer gases used for air infiltration measurements.

Reviews ideal characteristics of a tracer gas and gives literature review of the subject. Reports tests made on a house in California giving a direct intercomparison between common tracer gases used to measure air infiltration rates in buildings. Results indicate that air exchange rates measured using sulphur hexafluoride are slightly larger than thosemeasured using methane or nitrous oxide. The ratio of air change rates measured using sulphur hexafluoride to air change rates measured concurrently using a lighter tracer gas was found to be 1.10 +/- 0.10

The measurement of the rate of air change.

Gives an account of a method of measuring the ventilation rate of a room using hydrogen as a tracer gas. Describes katharometer used to detect the gas and the experimental procedure. Results agree well with those calculated by orifice plate method.

Measurement of ventilation using tracer gas technique.

Outlines ventilation measurements being made on two storey semi-detached houses using helium as a tracer gas. Describes measurement of decay rates in single rooms, the recirculation between two rooms and by summation the ventilation rate of thewhole house. Describes installation used to measure ventilation rates when homes are occupied without interfering with the normallife of tenants.

Energy conservation in an old 3-story apartment complex.

Reports study of the potential for energy saving in an old low-rise, 50 unit apartment building. Energy use and heat balance of the building are calculated including heat loss through conduction and air infiltration. Also gives estimate of infiltration rate from a room found using first water vapour thensulphur hexafluoride as a tracer gas. Suggests various strategies for energy conservation which would result in a 30% saving in fuel. Methods are applicable to a wider class of old buildings

Some field experiments with methods of estimating the ventilation rate in animal houses.

Compares methods of calculating ventilation rates in mechanically ventilated animal houses. Ventilation rates in several occupied animal houses were found by 1) measurement of internal to external temperature and moisture differences using a psychrometer;2) measuring decay rates of radioactive krypton as a tracer gas;3) estimating from manufactures rating of fans. Concludes that different methods agree to within the order of 5 or 10% and suggests the use of psychrometer techniques for simplicity.

Air infiltration in ten electrically heated houses

Gives measurements of air infiltration made in ten houses in Indiana using helium as a tracer gas. Assumes linear dependence of infiltration rate on temperature difference and wind velocity and calculates infiltration rate per unit crack length. Change rates ranged from about 0.6 to 1.5 changes per hour.

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