AIVC - Air Infiltration and Ventilation Centre

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air change rate

Air change rate measurement: the log/linear decay of tracer gas concentration with time.

A great deal of the literature on general ventilation expresses the adequacy of the volumetric flow rate of air in terms of the number of room air changes per hour. Although the concept of air change rate has very little relevance to the control of contaminants as it relates to the size of the room and not to the scale of the problem, the overall amount of air entering and leaving a workplace is of fundamental importance in assessing the quality of the working environment.

Natural ventilation analysed using dynamic simulation software.

The possibility of using natural ventilation for commercial buildings is increasingly being considered. To assist natural ventilation in these buildings atriums are often suggested for the building's design as well as mechanical systems providing low air change rates. To ensure that natural ventilation will meet today's comfort expectations the proposed design needs to be evaluated using dynamic simulation software.

The influence of ventilation on reactions among indoor pollutants: modelling and experimental observations.

This study examines the influence of ventilation on chemical reactions among indoor pollutants. We have used a one compartment mass balance model to simulate unimolecular and bimolecular reactions occurring indoors. The initial modeling assumes steady-state conditions. However, at low air exchange rates, there may be insufficient time to achieve steady-state. Hence we have also modeled non steady-state scenarios. In the cases examined, the results demonstrate that the concentrations of products generated from reactions among indoor pollutants increase as the ventilation rate decreases.

Performance of demand controlled ventilation: case study, energy savings and practical rules.

In order to assess the real performances of different demand controlled ventilation (DCV)systems, two of them were installed in meeting rooms of an office building.The first system is controlled by movement detection on terminal units and has been installedin a small meeting room which is regularly used.The second system is controlled by CO2 detection and frequency variation on fan. It has beeninstalled in a large meeting room (30 persons seated, up to 50 persons standing).The systems have proved to be energy saving with correct CO2 levels.

Natural ventilation air change rates considering atmospheric turbulence.

The estimate of actual air change rates considering atmospheric turbulence isintroduced. The starting point is the spectral description of turbulence - Kaimalspectrum was used in order to consider the height above ground. A set of syntheticwind velocity series are generated, out from a modified spectrum. The procedureconsiders an aerodynamic transfer function (a filter) where peculiar and cut-offfrequencies are determined by the general dimensions of the building and of theexternal openings, i. e., the turbulent scales of interest.

Energy efficiency of ventilation systems.

The paper presents a short description of the measurement program and the data collected for the “SynergieHaus”-project initiated by PreussenElektra and partners (now merged to E.ON). Results of airtightness measurements (ACH 50-values) are shown for a to

Indirect evaluation of indoor environmental parameters by means of audit techniques.

Some techniques aimed at the evaluation of microclimatic parameters through the measurement of other indoor physical quantities are critically reviewed. Particularly, the appraisal of the air velocity from the predicted mean vote and the determination of air change from the decay of the C02 indoor concentration are analysed. Important warnings for the use of these methods are underlined and the limits of applicability are pointed out.

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