Modeling Monetization of Collateral IAQ Improvements from UVGI for Coil Cleaning

Ultraviolet Germicidal Irradiation (UVGI) of cooling coils is done to control biofouling that can increase their flow resistance and decrease heat transfer coefficient. UVGI is also applied in air-handling units to improve indoor air quality (IAQ) by deactivating airborne microorganisms. A typical coil cleaning application delivers a smaller UV dose than an air treatment system, but should provide some collateral air treatment benefit. To date, this effect has not been studied. In this investigation, the benefit of air treatment provided by a cooling coil irradiation system is estimated via simulations employing a subset of the DOE Commercial Reference Buildings library. Benefits are quantified in terms of appropriate measures for each building type: reduced work-loss days (WLD) for office buildings, reduced disability adjusted life years (DALY) for schools, and reduced hospital acquired infections (HAI) for healthcare facilities. UVGI sized for coil cleaning results in a 2% to 12% average reduction in the measure of interest for each building. This reduction is negatively correlated with the average outdoor air fraction in each building type. Combining WLDs with US Gross National Income to monetize savings for Small, Medium, and Large Office Buildings yields between $2.10/m² and $6.61/m², $0.36/m² and $3.04/m², and $0.04/m² and $0.55/m² respectively. Combining DALYs with US Gross National Income to monetize savings for Primary and Secondary Schools results a wide range: $0.01/m² to $1.93/m² due to the large range of values one might reasonably assign to a DALY. In hospitals, Reduction in airborne HAIs resulted in estimated savings of $0.13/m² to $0.62/m².