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ASHRAE - 4831

Efficacy of Intermittent Ventilation for Providing Acceptable Indoor Air Quality

active, Most Current
Organization: ASHRAE
Publication Date: 1 January 2006
Status: active
Page Count: 9
scope:

Ventilation standards and guidelines typically treat ventilation as a constant and specify its value. In many circumstances, a designer wishes to use intermittent ventilation rather than constant ventilation, but there are no easy equivalencies available. This paper develops a model of efficacy that can determine how much intermittent ventilation is needed to get the same indoor air quality (IAQ) as the continuous value specified. This paper describes a simple relationship between three dimensionless quantities: the temporal ventilation effectiveness-which will be called the efficacy-the nominal turnover, and the under ventilation fraction. This relationship allows the calculation of intermittent ventilation for a wide variety of parameters and conditions. The relationship can be used to define a critical time that separates the regime in which ventilation variations can be averaged from the regime in which variable ventilation is of low effectiveness. The paper shows that ventilation load-shifting, temporary protection against poor outdoor air quality, and dynamic ventilation strategies can be quite effective in low-density buildings such as single-family houses or office spaces. The results of this work enable ventilation standards and guidelines to allow this extra flexibility and still provide acceptable indoor air quality.

Document History

4831
January 1, 2006
Efficacy of Intermittent Ventilation for Providing Acceptable Indoor Air Quality
Ventilation standards and guidelines typically treat ventilation as a constant and specify its value. In many circumstances, a designer wishes to use intermittent ventilation rather than constant...

References

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