How Monitoring the Behavior of HVAC Systems Can Support Filter Performance Assessment

A ducted air system is a common way to heat and cool an occupied building. Most devices in such systems - fans, ductwork, coils, chillers, etc. - have well-described relations to building thermal requirements and thermal characteristics. However, for one device category, air filters, the relation to thermal and other factors is poorly developed. Thermal requirements change filter airflows by season, but filter performance depends primarily on the combination of outdoor aerosol size distribution and concentration, the desired indoor air quality, and the numbers and activities of people in the building spaces. Filter pressure drop normally increases during its operating life, which complicates filter performance and affects other system elements. Fully instrumented studies of actual filter-containing systems over extended time periods are needed to develop the relationships between characteristics of a system and its energy usage, capital costs and operating costs. This includes the characteristics of indoor and outdoor particles affecting the performance of the air filters in the system.