Simulation and monetization of collateral airborne infection risk improvements from ultraviolet germicidal irradiation for coil maintenance

Ultraviolet germicidal irradiation of cooling coils controls biofouling that increases airflow resistance and decreases heat transfer coefficient. Though lower in power than air disinfection systems, coil ultraviolet germicidal irradiation systems should provide some collateral air treatment benefit. This benefit is estimated through monetization of simulated nonfatal illness spread in a group of commercial buildings. Benefits were quantified using appropriate metrics for each building type: work-loss days for office buildings, hospital acquired infections for healthcare facilities, and disability adjusted life years for schools. The pre-ultraviolet germicidal irradiation annual cost of occupant illness was the same order of magnitude as annual energy cost. Area-normalized cost was similar in magnitude for all buildings. The collateral air disinfection of coil surface ultraviolet germicidal irradiation reduced baseline illness costs by 3.5% or less, but the resulting cost savings exceeded the energy cost to operate the coil ultraviolet germicidal irradiation systems by as much as a factor of 20. The effectiveness of air cleaning methods already in place, such as ventilation and filtration, directly influences the incremental benefit of additional air cleaning measures.