Due to energy shortage and increased energy costs, there seems to be conflicting interest between hygiene and comfort on one hand, and energy economy on the other. Fortunately, it is possible to increase the ventilating air change rate in the zone of occupancy without increasing the air change rate for the whole room in question. Describes different methods for measuring and defining ventilation efficiency, and tests some of these methods in the laboratory, along with different ventilation systems.
Reports the results of measurement of ventilation efficiency in a full scale model of a small office with a diffuse air supply, which can be used to improve ventilation efficiency and therefore reduce air supply rates. Steady state and transient definitions of ventilation efficiency are given. Finds that ventilation efficiency depends on air flow rate and heat gain in the office. Higher air flow rates give lower pollutant concentration in the ocupied zone but also more mixing between the occupied and under-ceiling zones.
Describes a field method for surveying residences for indoor air quality. The method requires 2 days of field testing for each residence - a day to perform a multipoint tracer gas study to characterize the ventilation efficiency of the various spaces in the house and to determine the overall air change rate; and a day to measure contaminant concentrations in locations selected according to the results of the tracer gas study and contaminant generation locations. Describes and discusses results obtained by this surveying procedure in 3 energy efficient residences.
Notes that many air conditioning and industrial installations function inefficiently since too little attention is paid to air movement in a room. Compares effect of inlet and exhaust air devices. Considers reduced ventilation need if pollution can be eliminated or reduced. States that ventilation efficiency is an indication of how efficiently the air is used in the occupation zone and that the air supply to a zone determines ventilation efficiency. Illustrates various forms of ventilation.
Discusses principle that the position of supply air devices has a considerable influence on the ventilation efficiency that can be achieved. Considers factors affecting ventilation efficiency and different ventilation models. Illustrates different air supply systems.
Describes a series of experiments to determine the ventilation performance of 2 different models of wall or window mounted heat exchangers. Determines their nominal efficiency by the measurement of tracer gas decay rates at several indoor locations. Notes significantly higher local ventilation efficiencies in rooms where heat exchangers are operating. Some preliminary tests indicate that internal leakage between the air streams contribute significantly to the ventilation inefficiency of these systems.
Air change rate is often reported as a single number, with no attention paid to different values of air change rate in different zones of a building. This may affect air quality evaluation as there may be undetected zones where air change rate is too small, resulting in localized pollutant concentrations. Describes a multi-point tracer gas technique used to quantify air change ratein different zones of various residential buildings. Defines and calculates zonal ventilation efficiency terms, and proposes a criterion for analysis of the results for indoor air quality evaluation.
Uses a two-zone model to describe the concept of and to define the effectiveness of ventilation. Deals with multiroom aspects and procedures for measuring ventilation effectiveness. The simple two-zone model predicts generally high effectiveness for ventilating systems using the displacement principle, taking advantage of stratification. Reviews tests using thisprinciple in an office room for 1-3 people (28 sq.m., 2.8m ceiling height).
The concept of age, or residence time is applicable to characterize both how the supplied air or a contaminant is spread within an enclosed space and how quickly a contaminant is removed. Discusses the application of the concept toany enclosed space with air intakes and extracts. Establishes a direct relationship between the age concept, exposure to contaminants, and equilibrium concentrations. Treats different tracer gas techniques for measuring the age distributions and derived quantities.
Notes that ventilation efficiency is not referred to directly in the new DIF standards for ventilation effciency. Reasons for this are that there are no clear definitions for the term or instructions on how optimum ventilation efficiency can be achieved under different operating conditions. Describes some measurements carried out on ventilation efficiency in non-industrial premises.
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