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.
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.
The air infiltration associated with ventilation in buildings is recognized in ASHRAE Standard 62-1981, Ventilation for Acceptable Indoor Air Quality. In the light of recent trends toward increasingly tight housing, which limits air infiltration for ventilation, dependence on this source of outside air is onepoint that must be carefully considered in the Revised Standard. Other points to be considered are ventilation efficiency, necessary dilution of particulates and other pollutants, and how changes in humidity, air temperature and local heating may alter pollution levels in buildings.
This paper compares the conventional exhaust system with a supply-exhaust system with regard to the possible degree of control of the air exchange in the individual rooms. Ventilation efficiency and air exchange efficiency are defined and some examples show the local concentration, mean ventilation efficiency and mean air exchange efficiency for some simple ventilation schemes. Exhaust systems require a very tight building with small make up air openings. The ability of the different systems to avoid leakage out from the building of indoor air is also compared.
An account is given of what the kindergarten staff wrongly believed caused the problems and what measures they carried out in an attempt to solve them. On the spot measurements showed however what the real main cause of the problems was. Results from the comprehensive measurements of CO2 concentrations andother ventilation performance criteria in a room occupied by 12 children and 3adults are then presented.
Examines the effects of smoking rate, ventilation, surface deposition, and air cleaning on the indoor concentrations of respirable particulate matter and carbon monoxide generated by cigarette smoke. A general mass balance model is presented which has been extended to include the concept of ventilation efficiency. Following a review of the source and removal terms associated with respirable particulates and carbon monoxide, we compare model predictions to various health guidelines.
Discusses different ways of defining and comparing ventilation efficiency. It can be defined in absolute values ie the ability of the system to decrease the concentration of impurities in proportion to the maximum concentration. A time consta
Reports on symposium in Belgrade, 1978, on the consequences of blocked and contaminated ventilation ducts. Notes current research by Swedish Building Research Council into hospital ventilation systems and other work on aspects of contamination and its effect on efficiency. Also reports on investigations into ventilation in housing. Diagrams illustrate various parameters and the effect of cleaning and contamination on airflow and efficiency. Considers economic periodicity of cleaning. Stresses importance of cleaning heat exchangers. Article concludes with a subject bibliography.
Describes the general methodology for ventilation measurements by tracer gas, using decay, constant concentration and constant emission methods. Defines ventilation efficiency and the ways in which it can be experimentally determined. Gives the results of a series of lab measurements to determine the accuracy of the decay method under different conditions, and the efficiency of some mechanical ventilation systems.
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