English

Minimising ventilation for energy conservation in buildings requires that ventilation efficiency be high. The common practice of locating supply outlets and return inlets in or near the ceiling creates an opportunity for air tobypass from the supply to the return without mixing in the occupied space. Equations are derived for calculating efficiency and stratification factor from tracer gas decay measurements.

The paper shows that age analysing techniques are an excellent tool to assess ventilation effectiveness. It is important to differentiate between air exchange effectiveness and contaminant removal effectiveness, having continuous generation of contaminants. Only when a source is homogeneous andpassive, are the age of the air and the contaminants in the room equal. However, the air exchange effectiveness accounts for the removal effectiveness of the contaminant left in the room when the generation stops.

Examines evidence for relating sickness to the office environment. Notes research into the office building syndrome (obs) in various countries. Notes that although air conditioning goes back to the 1920s, obs has been in the news only during the last five years or so. Notes the contribution to this of energy saving regulations. Notes the complex nature of indoor air contamination. Points to obvious factors such as air conditioning systems unserviced for 30 years, occupational psychology, indoor architecture, climatic constance and air ionisation.

Looks briefly at current research into developing techniques for measuring and predicting natural ventilation and infiltration rates in buildings.

Notes that the information in the ASHRAE 'Fundamentals' volume on how much ventilation ought to be provided is based on work nearly 50 years old. Reports new work on permissible ventilation rates produced by H B Bouwman of the Dutch Research Institute for Environmental Hygiene of the Central Organisation for Applied Scientific Research TNO. The numerical purpose of the work was to find the rate of ventilation required to keep complaints from occupants of rooms about unacceptable smells to less than 5% or 1%.

Describes the technique employed, including the mathematical model as well as results from a validation test using an experimental chamber. The model assumes an exponential decay of the tracer gas concentration. The precision of the analytical procedure is estimated at better than 9%, while the error of the measured ventilation rate of the test chamber was 5%.

Studies the daily behaviour with respect to heating, use of windows and ventilation in newly built identical houses in Oosterhout, Netherlands. The houses have external walls of brick with cavity insulation, double-glazed windows and natural ventilation, with a gas burner furnace in the loft for heating and hot water. 57 occupants were interviewed and 41 filled in hourly log-books during 14 days recording people at home, thermostat setting, periods of open windows and trickle ventilators in the different rooms, use of radiator valves and position of doors inside the house.

A general multi-chamber model is presented and explored from the viewpoint of air quality studies. The model involves the following key concepts: purging flow rate and age distribution of both air and contaminants. From the physical and mathematical properties of the model, are deduced estimates of themagnitude of, and the relations between, the key concepts. The practical use of the model is illustrated.

Research was undertaken to provide buildings equipped with mechanical exhaust ventilation systems or natural ventilation with reasonable draught-free efficient ventilation. One possible solution for existing detached houses and multi-storey residential buildings is a supply air window. Recent research in Finland shows that, for the best method, about 6.0 dm3/s of outdoor air per light area m2 can be taken in through the wooden construction double-paned window without draught. The incoming air was heated to about 50% of thetemperature difference between the inner and outer air.

A tracer method was developed for the evaluation of workplace ventilation. Nitrous oxide or freon was used as the tracer. The concentration of the tracer gas was measured with an infra-red analyser. The versatility of the tracer technique for industrial hygiene applications was improved by the use of a microcomputer for data calculation, display and storage. Three applications are presented: 1. determination of the capture efficiency of a local exhaust hood, 2. the evaluation of the air leakage of a room, and 3. measurement of the local ventilation rates in a large industrial plant.