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.
HVAC UV lights are very effective at controlling mold inside the air handler. All mold in line-of-sight of the UV bulb will be killed, keeping the coil mold-free.
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. Sanuvox 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 UV stick 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 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.
Indoor Air Quality Priorities
While HVAC UV lights are effective for killing mold, bacteria, germs and odors, make sure you have completed the indoor air quality basics:
- Seal air ducts during renovation or construction
- Install ducts in conditioned space
- Ensure air-tight ducts, sealing all joints with mastic. See this Duct Sealing Guide from Building Science Corporation.
- Install high-MERV filters, but be sure your HVAC system is designed for the higher static pressure of better filtration
- Install UV light in HVAC system
- Conduct regular maintenance, changing filters monthly and cleaning the coil annually
HVAC UV lights:
- Control mold and bacteria
- Reduce colds and flus – germs are not re-circulated by HVAC system
- Reduce smells / odors
- Remove VOCs
- Are more effective in humid climates than dry climates
- Reduces clogging in condensate drain lines by preventing algae growth.
- Maintain a cleaner coil, improving cooling efficiency and reducing electricity costs.
HVAC UV lights are an effective means for improving indoor air quality, but only after following the indoor air quality priorities. Install an HVAC UV light and experience healthier indoor air quality.