"Continuous fan operation of the unit provides air filtration and circulation throughout the day, ensuring constant filtration of the room air. A greater latent capacity, when compared to conventional units, allows more moisture to be removed from the air, providing an atmosphere where the proliferation of molds and fungi is discouraged."

Airxchange (www.airxchange.com) manufactures energy recovery components for OEM integration in energy recovery ventilators, standard air handlers, custom units, rooftop units, accessories for rooftop and split system air conditioners, ceiling cassettes, wall-hung air conditioners and heat pumps, and perimeter systems (unit ventilators).

Bede Wellford, vice president of marketing for Airxchange Inc., Rockland, Mass., noted that often ventilation is reduced in school buildings either because of budget and energy concerns or an inability of the systems to maintain comfort during challenging design conditions, such as very cold days in the North or very hot and humid conditions on the Gulf Coasts.

"Energy recovery addresses both these issues and allows for more than the minimum rates to be introduced as desired to improve IAQ while reducing energy costs," he said.

Wellford pointed out three features that have a direct impact on IAQ. "First, the use of energy recovery to precondition outside air and save energy costs while reducing demand allows for the EPA-recommended ASHRAE 62.1 minimum ventilation rates in classrooms and lecture halls, gymnasiums, cafeterias, auditoria, etc.," he said.

"Second, enthalpy wheels handle the varying humidity load of the outside air, automatically adjusting the amount of sensible and latent work performed in response to outdoor conditions. This variable, sensible heat ratio is key to allowing the cooling equipment in the school to maintain space relative humidity at or near the design point of 50 percent.

"Absent a leak, flood, or building flaw, maintaining indoor relative humidity below 60 percent is generally acknowledged to preclude mold and mildew problems. Enthalpy recovery, used in conjunction with DX [direct expansion] equipment, provides a sensible heat ratio match that cannot be achieved with DX equipment alone.

"Third, our segmented, washable, replaceable heat exchange media provides for the ongoing and long-term maintenance of the ventilation system as now required by the ASHRAE standard.

"While the school environment is relatively benign (compared to a smoking-permitted restaurant, for example), all components of the ventilation and air-handling systems must be able to be accessed and cleaned on a periodic basis. Airxchange enthalpy wheel energy recovery components are unique in their ability to be cleaned and continue to do the latent work for which they were selected in the design."

Ruskin Co. (www.ruskin.com) manufactures dampers, louvers, and sound absorbers that are ideal for use in schools, said Robert Van Becelaere, vice president of Engineering for the Ruskin Co., Kansas City, Mo.

"We have dampers and louvers that are designed to measure and control the outside air entering the HVAC unit," he said. "We have spec sheets available on IAQ50, AMS50 and EAML6625."

Publication date: 08/02/2004