Date: 16/07/2018
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8 Downsides to UV Lights

Mold in your home can be an unsightly and smelly problem, as well as a major health issue.  Despite what others may tell you, adding UV lights to your HVAC system will not completely solve an air quality or mold problem in your home.  In this post, we’ll help explain why and point out some of the downsides of UV lights.



  1. UV lights are costly to install – upwards of $1500 - and costly to operate as they need frequent replacement.  The light bulbs themselves are not cheap (about $100) and they may need to be installed by a professional, so will require a service call.
  1. any retrofits of UV lights in home HVAC systems are less than effective for a variety of reasons.  Many installers do not use bulbs that are intense enough or do not use enough bulbs to do much good (depending on the size of the duct and volume of air, you may need as many as 6 bulbs!).  Placement and direction of the lights is also a concern and impacts the effectiveness.
  1. The UV light only functions to clean the air that goes through that particular portion of the system where the UV light is.  If the leak in your ductwork (which is the source of the mold or odor) is past that point, it won’t matter whether you have a UV light or not!
  1. Millions of droplets of bacteria and viruses are released into the air when someone in the room sneezes or coughs.  Most large droplets tend to fall to the ground before going through the HVAC air handler.  Smaller droplets can remain suspended in the air for hours or days, circulating throughout your home, before coming into contact with the UV light in the HVAC system. Millions of mold spores are contained in dust that is deposited on your furniture and linens and never go through the HVAC ductwork and so do not come into contact with the UV light.
  1. The blower/fan in your air handler does not typically function all the time. The system cycles on and off throughout the day in order to maintain the desired temperature.  Any time the fan is not blowing, the air is not passing through the UV light and so it is not being cleaned.  If you do operate your HVAC’s fan 24x7 (switch it to “On” rather than “Auto”), this will help, but it will increase your electric bill.
  1. In a typical home HVAC, the air is not in contact with the UV light long enough to cause eradication of all pathogens. Some commercial HVAC systems – such as those for hospital surgical suites – may be more specially designed for this.
  1. UV lights do nothing to clean particles in the air like dust, pet dander, and other allergens. In some cases, they may even increase ozone in the air, which itself is a pollutant.
  1. UV lights do nothing to address the source of the mold and mildew in the environment – humidity!  You may need to make investments in home repairs and improvements, or make lifestyle changes. Use exhaust fans when showering and cooking. Fix plumbing or roof leaks. Replace the seals around the tub, shower, or windows where moisture collects. Get the basement or crawlspace waterproofed or install a sump pump. Address drainage issues or standing water around your home’s foundation.  Do not allow your HVAC’s condensate drain line to get backed up.  Not only will UV lights not alleviate any of these potential mold problems, just having a UV light may make it easier for the homeowner to overlook fixing the real cause of their mold issues.

Sadly, some HVAC companies just want to sell more gadgets to gullible homeowners to increase their revenues. This is why having a reputable HVAC service company you can trust is so very important.  At Interstate AC Service, our technicians are not paid on commission and we’ll never sell you something you don’t need!  

If you live in the Nashville or surrounding area, please call us for all your heating, air conditioning, and air quality needs, at 615-832-8500.