English

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.

Gas phase filters were installed within the air handling unit of a HVAC system feeding 100 % fresh(outdoor) air to an office building. The filter efficiency for ozone (O3) and nitrogen oxides (NO2 and NO) was measured continuously over a one year period as a function of time (filter's life) and outdoor air parameters (temperature and relative humidity). The results show that the filter efficiency varies with time and depends on the temperature and relative humidity of air.

Recent studies have demonstrated the influence that air jets in rooms ventilated by chilled beams have on draught-related thermal sensation. The most critical zone in which people often suffer draught sensation is located near a wall and close to the floor. To avoid the draught sensation, the critical velocities of the returning air jet should be specified and determined before the jet enters the occupied zone. In this study, the velocity of the attached plane jet was modelled and measured at six heights and at eight different distances from the wall.

The natural ventilation of a building, flanked by others forming urban canyons and driven by the combined forces of wind and thermal buoyancy, has been studied experimentally at small scale. The aim was to improve our understanding of the effect of the urban canyon geometry on passive building ventilation. The steady ventilation of an isolated building was observed to change dramatically, both in terms of the thermal stratification and airflow rate, when placed within the confines of urban canyons.

In the case of cross ventilation through a large opening, it is well known that the inflow direction at the opening is not normal to the opening. A simplified prediction method for simultaneously predicting the inflow direction at the inlet opening and the airflow rate is presented. It is also well known that the use of general discharge coefficient values (CD) is not suitable for the calculation of cross ventilation rate. The first reason is that the simple connection of the pressure loss coefficient of an opening (?