AIVC - Air Infiltration and Ventilation Centre

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air infiltration

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.

The effect of wind speed upon heat requirements and internal temperature.

Sets out simplified analysis of thermal load imposed by infiltration of cold outside air into interior of heated building as function of prevailing wind speed and difference between internal and external temperatures. Treats infiltration loss, structure loss, effect of wind speed on loss. Summarises these values in tables. Concludes incidence of wind speeds in excess of those used for calculation of heat losses at design condition can have a significant effect on internal temperatures. Notes implications for non-attainment of design temperatures in intermittently heated buildings.

Effect of leakage in buildings on ventilation and energy demand. Rakennusten tiiviyden vaikutus ilmanvaihtoon ja sen energiankulutulseen.

Ventilation losses account for approximately 50% of heat consumed by a building. Treats characteristics of leakage generally. Estimates that decrease of ventilation of building stock in Finland by 0.1 air changes per hour would save about 100 million f marks annually. Provides practical instructions for controlling building leakage rates.

Wind, temperature and natural ventilation - theoretical considerations.

Discusses in theoretical terms complexity of interactions of weather-driven air infiltration by 1) wind and 2) convection induced by indoor/outdoor temperature difference. Notes implications for practice of this complexity such as near impossibility of achieving accurate computer models. Treats flow through a single crack. Illustrates diagrammatically and discusses nature of the interaction of the 2 effects for several idealised examples. In an appendix proves mathematically the subadditivity of the effects for a wide class of situations.

Measurement of air tightness of houses.

Describes pressurization method of measuring air leakage using a fan installed through an open window. Gives results of survey of 24 houses. Humidity, meteorological parameters, indoor particulate levels, measured equivalent leakage areas and other information were recorded. Finds that tight houses tend to havehigher humidity, that leaky houses require more heating energy and that houses where smoking takes place have higher air pollution levels than others.

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