This paper describes the classical approach for calculation of wind driven airflow through large openings in buildings and discusses the fulfilment of the limiting assumptions. It is demonstrated that the limiting assumptions are not fulfilled for large openings in buildings for cross ventilation, and therefore, the classical approach is not appropriate for prediction of airflow through large openings in buildings in the cross ventilation case. Using the approach for real openings and estimating the discharge coefficient for window openings has also not been very successful.

Measurements of the unsteady flow in a ventilation stack of a school have been made at model scale in an environmental wind tunnel. The results confirm the expectation that the stack is well-sited, in that it was difficult to induce flow reversal except over a narrow range of wind directions and the amount of reversal was small (reversal percentage < 5 %). The results also show that the technique is capable of reliably detecting such small reversal percentages.

Age-of-air is a technique for evaluating ventilation that has been actively used for over 20 years. Age-of-air quantifies the time it takes for an elemental volume of outdoor air to reach a particular location or zone within the indoor environment. Age-of-air is often also used to quantify the ventilation effectiveness with respect to indoor air quality. In a purely single zone situation this use of age-of-air is straightforward, but application of age-of-air techniques in the general multizone environment has not been fully developed.

Several studies have suggested that recommended ventilation rates are not being met within schools. However these studies have not included an evaluation of whether or not this failure might have an impact on pupil performance and learning outcome. The work reported here was designed as an initial investigation into this question. Using the Cognitive Drug Research computerised assessment battery to measure cognitive function, this study demonstrates that the attentional processes of school children are significantly slower when the level of CO2 in classrooms is high.

This paper reports on tracer gas measurements of the ventilation flow within a low-energy building.Constant-concentration, decay and homogenous tracer gas emission methods were used. Low-energy buildings are airtight constructions; effective ventilation is thus very essential for the indoor climate. The results of this study show an airflow rate between 0.42 and 0.68 air exchanges per hour (ac/h), which should be compared to the minimum requirements in Sweden of 0.5 ac/h.

A healthy indoor environment with sufficient fresh air is a prerequisite for the well-being and highproductivity of building occupants. Carbon dioxide (CO2) based Demand Controlled Ventilation (DCV)optimizes and resolves the traditional conflict between reducing ventilation to save energy while maintaining adequate ventilation for air quality. Therefore, in conditioned spaces where occupancy levels vary, CO2 based DCV can prove to be an energy efficient method for meeting ventilation needs while maintaining good IAQ. Furthermore, an economizer cycle can be used to save cooling energy.

The rationale of an advanced natural ventilation system should be to control airflows and air temperature during winter, and to avoid unnecessary energy losses and local draught, while maintaining an adequate ventilation rate. On the other hand, natural driving forces (pressure head due to buoyancy and wind) vary significantly during the heating season.

The present study is focused on the relation between wind speed and air temperature during the summer period over the greater Athens area. Specifically, hourly air temperature data, recorded at 27 stations, were studied for June, July, August and September between 1996 and 1998. These data were related to the corresponding mean hourly values of wind speed, which were measured by the National Observatory of Athens. A small increase in air temperature in relation to increasing wind speed was found for daytime and night-time periods.

It is known that discharge coefficients vary with wind direction and opening position. The local dynamic similarity model of cross-ventilation can select discharge coefficients on this basis. This paper summarizes previous studies on various inflow opening conditions, and describes new studies on outflow openings and the evaluation of ventilation flow rates in two zones based on coupled simulation of the local dynamic similarity model and a simple network model.

A wind catcher/tower natural ventilation system was installed in a seminar room in the building of theSchool of Construction Management and Engineering, the University of Reading in the UK. Performance was analysed by means of ventilation tracer gas measurements, indoor climate measurements (temperature, humidity, CO2) and occupant surveys. In addition, the potential of simple design tools was evaluated by comparing observed ventilation results with those predicted by an explicit ventilation model and the AIDA implicit ventilation model.