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The Impact of Desiccant Dehumidification on Classroom Humidity Levels
June 2002
Hugh I. Henderson
Adam C. Walburger
CDH Energy Corp.
Cazenovia, New York

James R. Sand
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831

Abstract: Desiccant-based dehumidification technologies offer the potential to provide improved IAQ in schools by properly controlling space humidity levels while also providing the 15 cfm (7 L/s) of ventilation air per student required by ASHRAE Standard 62. This paper reports field test results from a school near Kansis City, Kansas, that was retrofitted with a desiccant system. Monitoring equipment was installed to monitor energy use and space conditions in the desiccant-treated classrooms as well as two other similar areas that used conventional HVAC equipment. Measured space humidity levels were shown to be 15 to 20 gr/lb (2 to 3 g/kg) lower in the desiccant area than in other areas with the same ventilation rates. Classroom areas that provided only 5 cfm (2.3 L/s) of ventilation air per student were found to maintain acceptable humidity levels in the space. However, areas that used conventional HVAC equipment to provide 15 cfm (7 L/s) per person were shown to have much higher humidity levels. All studied areas, including the desiccant-treated area, had unacceptably high humidity levels during the unoccupied periods (nights, weekends, and summer break). In order to provide good IAQ in classrooms, humidity control must be provided continuously to minimize the risk of biological contamination. The desiccant unit installed in this test was configured as a ventilation pretreatment system, so dehumidification could not be provided independently of ventilation. For desiccant technology to realize its full potential in schools, packaged systems must be configured and applied to allow for dehumidification during both occupied and unoccupied periods.

Keywords: desiccant dehumidification, indoor air quality, IAQ, humidity control, ASHRAE Standard 62

American Society of Heating, Refrigerating, and Air-Conditioning Engineers

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ASHRAE Transactions 2002
Vol. 108, Pt. 2
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