In 1903, Niels Finsen won the Nobel Prize in Medicine for his use of ultraviolet light in the treatment of tuberculosis. Since then, ultraviolet lights have been widely adapted for all kinds of uses: sterilizing hospitals, sterilizing water, germicidal lamps in food establishments, and even curing nail polish faster. If UV light is so effective, how can it be applied to improving indoor air quality for residential HVAC systems? Will it kill mold and bacteria in HVAC systems? Yes, but you need to understand the priorities of indoor air quality and the types of UV lights available for residential HVAC systems.
Types of HVAC UV Lights
There are two types of UV lights for HAVC systems.
Coil Sterilization – A “stick type” light installed inside the return air duct near that sterilizes the air handler coil. A coil sterilization UV light runs 24/7 and is the most common type of HVAC UV light.
Air Sterilization – A complete UV light unit that sterilizes moving air. The UV light unit is installed in the return air duct and cycles on with the air handler blower. Honeywell is a top-rated manufacturer of air sterilization systems.
Studies Prove Effectiveness
Two studies point to the effectiveness of UV light in killing mold and bacteria, one in hospitals and the other in a commercial HVAC system.
Ultraviolet Light Effective in Hospital Infection Control – In 2012, Researchers at Duke University Medical Center used ultraviolet radiation (UV-C) to nearly eliminate drug-resistant bacteria in 50 hospital rooms, reducing the number of bacteria by more than 97%.
Effectiveness of Germicidal UV Radiation for Reducing Fungal Contamination within Air-Handling Units – In this commercial office building, and after 4 months of operation, “the fungal levels following UV operation were significantly lower than the levels in control AHUs (air handler units).”
The Honeywell 1059A UV light bulb is estimated to last 9000 hours, just over 1 year. Replacement bulbs cost about $70. Replace the bulb during each annual HVAC service and maintenance is nearly effortless.
The Honeywell 1059A UV light we installed is rated at 1.1 amps. To calculate annual energy costs, I used these handy calculators:
Convert Amps to Watts – 24v AC at 1.1 Amps = 26.4 Watts
Convert Watts to Electricity Cost – 26.4 Watts * 24 hours/day * 10.5 cents kWh = $24.28 per year ($2.00 per month)
For just under $100 per year ($24 electricity + $70 replacement bulb), my family has peace-of-mind knowing that we are breathing the highest-quality indoor air. It seems like a small price to pay. But it doesn’t make sense to install an HVAC UV light unless you’ve followed the indoor air quality priorities.