AIVC - Air Infiltration and Ventilation Centre

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air change rate

Air infiltration and our thermal environment.

States that application of further thermal insulation to house structures increases importance of ventilation heat loss, from around 20% to nearly 50% of total design heat requirement. Any further energy savings will be by minimising ventilation components. On basis of British Gas research results and others, illustrates sources and mechanisms of infiltration to give an insight into problems it may cause in future housing. Treatseffect of weather, ventilation rates. Among conclusions states increasing attention will have to be paid in future toinfiltration.

The development of tracer gas methods for measuring air changes. Utveckling av spargasmetoden for matning av luftvaxling.

Notes principle of air change rate measurement using natural growth exponential equation to measure concentration of tracer gas. Experience shows that period required for satisfactory measurement is often periodicity of air change rate. Diagram relates linear and logarithmic scales used in air change equation. Describes use of pre-programmed gas analysis equipment allowing extrapolation to forecast results. Uses microprocessor for evaluation. Also discusses importance of instrument calibration.

Ventilation in single family dwellings - a system analysis. Ventilation i smahus - ett systemanalys.

Describes sealing houses against air infiltration to allow controlled ventilation. Notes inherent risks in poor ventilation such as high radon content and its associated decay products, poor air quality, moisture, condensation, mould and allergy-producing dust particles. Treats requirements in swedish building code and stipulated minimum air change rate. Comprehensive series of graphs illustrates air change rate as function of wind speed and different grades of building air tightness.

A review of experimental techniques for the investigation of natural ventilation in buildings.

After discussing briefly the principles of natural ventilation, goes on to describe tracer gas techniques, air movement measurements, and various model techniques including analogues. Advantages and disadvantages of each method are indicated, andtheir suitability for particular applications.

Ventilation measurements in houses and the influence of wall ventilators.

Using nitrous oxide as a tracer, the author made 390 measurements of ventilation rates in seven closed rooms of six houses, in Melbourne, Australia. Half of the observations were taken when the wall ventilators were sealed, in order to explore their influence on room ventilation. Results for each room, grouped in ranges of wind direction and according to whether ventilators were open or closed, are shown as regression curveson plots of ventilation rate against wind speed. The ventilators are shown to have only a slight effect on ventilation.

Solution of the main equation of air changes with respect to air flow rate.

Points out mistakes in text book formulae for determining the flow rate of fresh air. Provides a new approximate formula for this. Establishes a differential equation for air change rates and derives a generalized equation for ventilation incorporating only three parameters. Provides curves for determining the fresh air flow rate and gives calculated examples.

Some problems in calculating ventilation heat losses. Problemy vypocti tepelne ztraty infiltraci.

Describes methods of calculating ventilation heat losses employed in several European countries. Compares them from standpoint of air change rates. Proposes calculation procedure for new Czechoslovak standard CSN 06 0210.

Air change rates in buildings. Byginingers luftskifte

Summarises results of research project comprising survey of air tightness and natural air change rates in various types of residential building. Briefly describes equipment for pressurization tests and tracer gas measurements. Compares properties, range of measurement and cost of 5 different tracer gases. Provides some results from measurements in 53 single family houses and 28 flats. 9 of tested dwellings had their tightness improved and supplementary measurements made.

Economic ventilation of single family houses. Ekonomisk ventilation i smahus.

Outlines necessary ventilation rates for an occupied room. Discusses natural ventilation of a room through openings in the ceiling. Discusses natural draught ventilation for single family houses, combined natural draught and mechanical ventilation, mechanical fresh air ventilation based on a central duct, fortuitous ventilation caused by air infiltration and leakage. Compares natural and mechanical ventilation. Considers supplyair systems for single family houses, warm air heating and possibilities for heat recovery.

Field studies of dependence of air infiltration on outside temperature and wind.

Expresses air infiltration rate measured using tracer gas in 2 similar town houses in terms of wind speed, wind direction, indoor-outdoor temperature difference, average rate of boiler firing and fraction of time that doors are open. Method yielded reproducible rates of air infiltration within 0.1 air exchanges per hour in any single one-week run once outside temperature, wind speed and wind direction were allowed for. States results partly reveal set of physical principles determining house air exchange rates which are so far poorly understood.