The constant concentration tracer gas (CCTG) technique is typically used to measure air infiltration rates in mulitzone buildings. The measurements are performed by injecting metered amounts of a tracer gas into each zone so as to keep all the zones at a target concentration. One drawback to this method is that no information is gained about the level of interzone flow rates in the building. Modified constant concentration techiques are described which allow selected infiltration and interzone air flow rates to be estimated.
This paper describes one of the results of the IEA-annex 8 "Inhabitants behaviour with regard to ventilation". Annex 8 has shown that the occupants can play a rather important role with regard to the ventilation rates inoccupied buildings. This paper gives some practical 'rules of thumb' for estimating air flow rates through open windows. An overview of measured and estimated ventilation rates in houses is given from which a simplified approach is derived that takes into account the air tightness of the building and the behaviour.
A simplified pocket calculator model has been developed which can simulate the air flow distribution in multizone structures. The model is based on lumped parameters and includes several assumptions to simplify the description of air flow due to wind and stack effect and their superimposition. This paper gives a brief overview of the model and describes several applications. Results obtained from a mainframe based research tool. The examples show that the simplified method can be used to predict air mass flows within reasonable accuracy for different types of buildings.
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