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.
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.
The multiple spaces equation of ASHRAE Standard 62-1989 makes it possible to bring in a smaller fraction of outdoor air than that dictated by the critical space. This paper develops an analytical proof that increasing the primary airflow rate to t e critical space reduces the outdoor airflow rate required to meet ventilation requirements. For systems employing fan-powered boxes, where more than one box is critical, a systematic procedure for incrementally increasing the primary air is currently required.
Dampness in residential buildings is detrimental to the health of the occupants and causes the growth of mold and decay in the fabric of the building materials. In Taiwan the average winter relative humidity is 80% and the average temperature is 15°C (59°F). It has been found that the average winter indoor moisture content in Taiwanese apartments can be higher than the outdoor content by as much as 15%. Although the main cause for the increased indoor humidity levels has not been identified, removing the moisture generated from shower baths can help reduce the humidity.
As part of a recent ASHRAE research project (781-RP), a thermal sensation prediction tool has been developed. This paper introduces the tool, describes the component thermal sensation models, and presents examples of how the tool can be used in practice. Since the main end product of the HVAC industry is the comfort of occupants indoors, tools for predicting occupant thermal response can be an important asset to designers of indoor climate control systems. The software tool presented in this paper incorporates several existing models for predicting occupant comfort.
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