Results from a two-box model for calculation of tracer gas concentrations in rooms are given and consequences of different definitions of ventilation efficiency are discussed. Results from three different series of experiments are presented.
Based on current concerns regarding indoor air quality and energy use, there is a need for in situ techniques for evaluating buildings' infiltration and ventilation characteristics. The U.S. National Bureau of Standards has developed and employed equipment and techniques for such evaluation. The measurement of whole building leakage and ventilation rates has been reported on previously. Additional procedures are presented here for a more complete evaluation of the ventilation system operation and the distribution of air within the building.
The various meanings of ventilation efficiency are briefly summarised. The residual life time of a released tracer gas is chosen as the most meaningful and convenient basis for local efficiency measurements in large, occupied, mechanically ventilated buildings. Measurements were carried out in ten public swimming pool halls. Sulphur hexafluoride tracer gas was released from a 20 ml syringe at various locations around the pool hall and the integrated concentration with respect to time was measured at the exhaust air duct. This was extrapolated to infinite time using the measured decay rate.
The performance of whole-house mechanical ventilation systems was explored in an full-scale indoor test house (volume 176 m³ ) . A range of parameters were monitored: * The pressure distribution * The inflow of outdoor air to each room, the mean age of air in each room and the air-exchange effectiveness * The spread of a 'contaminant' released respectively in the kitchen and in the bedroom. The tests were undertaken both with the internal doors closed and with the internal doors open. Both mechanical extract system and balanced (combined) systems were tested.
A steady state multi-cell calculation model has been developed in order to predict the interconnection between airtightness and ventilation rates. The model has been tested with measured leakage data of a detached house.
Ventilation efficiency was measured with freon gas in 3 large industrial buildings under normal working conditions. Size of building varied from 3000 to 10000 m2 and room height from 5-19 m. The ventilation systems were of 3 types: 1. Overhead fresh air supply network with conventional air inlets, 2. Fresh air supply direct to occupied zones by a low impulse system, and 3. Overhead fresh air supply distributed by the Dirivent system. Describes techniques of tracer gas measurements. Illustrates some results in graphs.
When indoor air concentrations from indoor combustion processes are estimated, source strengths and ventilation rates are usually considered. Recent studies, conducted in the Energy Research House at Iowa State University, indicate that seve
Based on the age concept, the performance of the following three principle ventilation schemes have been monitored (supply air terminal - extract air terminal), ceiling-ceiling, ceiling-floor, floor-ceiling. All systems used only air for both heating and cooling. Contaminants with both greater, less and approximately the same density as air were released at a point source. The tests were both carried out in an empty room and with a person (heated mannekin) in the room.
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