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Finding Fall IAQ Opportunities

When temperatures are mild, indoor air quality (IAQ) begins to suffer. When heating or cooling demand ceases, necessary functions such as ventilation, dehumidification, and filtration terminate as well. However, some opportunities exist:

Ventilation. Some ventilation can be provided from open windows and introducing outside air into the building. This air is unfiltered, and contains excess humidity. Installing fresh air systems with filtration and dampers is one opportunity. Installing a thermostat that cycles the fan for ventilation is another service that solves the problem.

In fall, check small bath and kitchen exhaust fans. These lead to cleaning and replacing exhaust fans. Cleaning a small fan often quadruples airflow, having a huge impact on moisture and odor removal from the areas they serve.

Dehumidification. Consider recommending de- humidification systems to continue the necessary moisture removal when systems are off, especially in the Southern and Eastern U.S. Several manufactures are introducing some exciting new equipment with dehumidification capabilities. Of course, once the heating systems kick in, dehumidification will begin again. The question is, how much damage can occur in the building until that happens?

Filtration. Most filtration systems accomplish nothing unless air is passing through them. Filtration ties in closely with ventilation, but should also be considered as a stand-alone system component. Choose your filters and size them carefully. The number one concern with filtration is excessive pressure drop. As filter efficiency increases, static pressure increases. The higher the static pressure drop through filters, the lower the system airflow. Install new filter housings to increase filter surface area and decrease pressure drop; or install return air filter grilles. The filter installed to increase air quality actually can be the primary culprit in causing extremely poor indoor air quality. For constant speed fans, the NCI pressure budget is only 20% of the fan rated total external static pressure.

Check installed filter static pressure drops to assure the fan pressure remains below the fan rated pressure.Many high efficiency filters may require that two or more filters be installed, to assure the pressure remains lower than fan rated pressure.

Rob “Doc” Falke serves the industry as president of National Comfort Institute, a training company specializing in measuring, rating, improving, and verifying HVAC system performance. He can be reached at [email protected] or at 800/633-7058. Visit NCI’s website at for more information.

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