Modern one-family houses in Scandinavia built before 1980 are often naturally ventilated and heated by electric baseboard heaters. The overall supply of fresh air is often inadequate during the heating season in many of these houses. Long periods of time individual rooms might get too little fresh air. The performance of a natural ventilation system is very much dependant upon the overall airtightness and the distribution of the airtightness of the building and the weather.
This paper extends the integral mass balance approach to the remaining constant concentration technique. An integral formulation of the constant concentration problem is presented that accounts for the possibility of variation of tracer concentration. This approach leads, in principle, to data reduction strategies that may be expected to improve the accuracy of the constant concentration technique and that may be used to isolate those portions of a given constant concentration data set that are likely to be most reliable.
Modern one-family houses in Scandinavia are often ventilated by an exhaust fan. Most of the outdoor air probably enters through whatever cracks and openings there are and only a small part enters through the supply vents in many of these houses. The overall supply of outdoor air might be adequate, but some rooms often do not get enough of outdoor air. The constant concentration tracer gas technique was used to examine the supply of outdoor air. Fan pressurization combined with infrared photography were employed to characterize the air leakage of the building.
Ten years ago the automated constant concentration tracer gas (CCTG) method was conceived at the Technological Institute, Tastrup, Denmark. This technique is now used by researchers toexamine a wide variety of air infiltration and ventilation related problems. At this juncture it would seem appropriate to summarise the development of the CCTG system and examine its use in present day research.
More than two months of detailed test data have been gathered using modified constant concentration tracer gas techniques for a six-storey, 60 apartment, multi-family building. Weather, and interior conditions in the building were part of the data set. Because of occupant effects, large changes in air exchange rates were observed, often over short time period. The test apartment allowed us to evaluate the influences of weather alone with the added feature to employ controlled window openings.
The air exfiltration part of ventilation is often difficult to determine and its part of the energy balance is therefore usually determined as a remainder or given a constant value. This paper examines ventilation systems in six different modern houses. The constant concentration tracer gas technique tended to underestimate the total ventilation. A simplified theoretical one-zone model made accurate estimations of the air exfiltration. For detailed information on air flows a multi-zone network model was useful.
1979 a project was launched at Technological Institute, Copenhagen with the purpose of developing a method for continuous measurement of air change rates in occupied dwellings. Today - 10 years later - we can introduce the first generation of mass-produced measuring equipment performing measurements of air change rates employing the method of constant concentration of tracer gas. The principles used in the first model, which was introduced 1981, are largely identical to those used in the latest model.
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