DOE EERE Research Reports

Fortunately, as shown by this investigation, much credible research has already been conducted. Based on these scientific data, it can be concluded that most IAQ problems can be avoided (or resolved) by providing an adequate amount of outdoor air on a continuous basis, controlling space relative humidity so that it seldom exceeds 60% or drops below 30%, and using a level of outdoor air infiltration efficiency necessary to prohibit most mold spores and fungi from entering the HVAC system.

The research conducted to date confirms that proper outdoor air ventilation and humidity control are necessary. Too often in practice, one is obtained at the expense of the other. Packaged systems that provide the outdoor air volume only when the coil is energized improve humidity control but allow indoor contaminants to build to unacceptable levels. The same equipment can be operated with the supply fan running continuously and with an outdoor air damper adjusted to provide the required quantity of outdoor air, but humidity control is lost, especially at part-load conditions. Fortunately, proven and cost-effective system solutions exist that allow satisfaction of both the continuous ventilation and the humidity control objectives while they provide a central location for effective outdoor air filtration, which can be easily accessed for routine maintenance.

In summary, the research identified as part of this investigation provides the basis for the formation of a simple hypothesis: Most IAQ problems in school facilities can be avoided by (1) providing adequate outdoor air ventilation on a continuous basis (15 cfm per student), (2) controlling the space relative humidity between 30 and 60%, and (3) providing effective particulate filtration of the outdoor air.