Reports results of studies conducted in Switzerland in small apartment buildings. Air change rates were measured in ten different apartment buildings using N2O as a tracer gas. Measurements were taken for various wind conditions andtemperature differences and with the windows partly open. Finds that ventilation rate increased by a factor of 4 when the windows on one facade were opened by only a few centimetres.
Proposes a method for measuring the rate of air change in factories using ammonia as a tracer gas and measuring its rate of decay by a colorimetric method. The advantage is that extremely small quantities can be detected. The method is cheap, easy to use, reasonably accurate and unobjectionable to the occupants.
Discusses the principles involved in measuring air change rates using tracers and gives the theory. Outlines the preparation of the tracer and the test procedure in stables. Finds that satisfactory results can be obtained when the concentration of krypton-85 is only one tenth of the maximum allowable. Lists the advantages of the method.
Points out that increased levels of thermal insulation in dwellings make ventilation heat loss an increasingly significant proportion of total dwelling heat loss and of great significance for sizing heating installations and selecting their control equipment. Treats attempts to reduce ventilation loss by specifying greater tightness of building structures, especially windows.
Reports investigation of air change rates in two residences using helium as a tracer gas. Gives results of measured air change rates, wind speed and direction and internal to external temperature difference. Uses statistical method to compare results from the two residences and concludes that temperature coefficients were statistically different but that wind coefficients were not. Finds high dependence of infiltration rates on indoor to outdoor temperature difference and that values for air leakage obtained from current methods of estimation were lower than those actually experienced.
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.
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.
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.
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.
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
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