English

A number of approaches exist to evaluate building ventilation and indoor air quality. In some situations, the measurement and analysis of indoor carbon dioxide concentrations can be useful for understanding indoor air quality and ventilation. On the other hand, oversimplified descriptions of measurement procedures based on carbon dioxide have been presented, and there have been many instances in which indoor carbon dioxide concentration measurements have been misinterpreted and misunderstood.

This paper presents results of a project initiated by ASHRAE and the National Research Council of Canada. The project applies both physical and numerical modeling techniques to atrium smoke exhaust systems to investigate the effectiveness of such systems and to develop guidelines for their design. This paper compares experimental results obtained from testing a physical model of a mechanically exhausted atrium space with results of two sets of numerical predictions of the same space.

Custom software to automatically administer questionnaires on computer screens was installed on computers in four open-plan offices. Five questions related to thermal comfort were presented twice per day for three months. Results indicate that this new method of subjective data collection was successful and efficient: the participants had few complaints about the method of questionnaire delivery, and a substantial literature review demonstrates that our results are comparable with results from other field studies of thermal comfort conducted using different methods.

Many ventilation requirements and recommendations are in the form of outdoor airflow rates per person. Ventilation systems are therefore designed to provide a minimum level of outdoor air based on the designed occupancy level multiplied by the per-person ventilation requirement. Because the indoor generation rate of carbon dioxide is dependent on the number of occupants, it has been proposed to use indoor carbon dioxide concentrations as a means of controlling outdoor air intake based on the actual number of occupants in the space as opposed to the design occupancy.

The design of low-energy office buildings requires specific attention to an energy efficient concept for providing good indoor air quality conditions. With this respect, mechanical ventilation shows undeniable advantages: it can be optimally controlled (infrared detection, CO2 control,...), heat recovery is applicable, outdoor noise and pollution penetration can be minimised. Another crucial challenge in low-energy office buildings is avoidance or, if possible, the minimisation of active cooling needs.

The main source of humidity in office buildings is the human occupant. Moisture is therefore a result of heat transmission from the person to the room air. The article covers heat transmission of the human body, humidity and comfort, cooling and dehumidification, and refrigeration capacity.