Radon fans run constantly, which means if you have a noisy one it’s gonna drive you nuts. One of the most popular questions we get asked from the general public is “how noisy is my radon fan?” or “how do I pick a quiet radon fan?” The answer is: it depends. 
Noise factor: Contractor Skill
Noise depends on a number of factors. The greatest factor is the skill of the contractor installing it. Many DIYers or untrained contractors simply buy the “biggest” fan they can afford and slap it on their system. Adding a fan that is too large for your home is a disservice to the occupants and the environment. Bigger fans are noisier, they waste energy, and they cost more. If you do the math, using a high suction radon fan instead of an energy efficient medium flow fan like the Rn2EC can mean 100+ watts of energy wasted. That’s over $1,000 in lifetime run costs in most parts of the USA. Read my article on why fan sizing is so important and why many contractors—even those with the skills to do so—don’t include precision radon fan sizing in their quotes in my here.
Noise factor: building materials
A radon fan that exhausts to PVC will sound different than one that exhausts to metal gutter material. Homes with 2×6 exterior walls will experience noise differently than those with 2×4 exteriors. Vinyl and stucco siding each reflect and absorb noise in different ways. Is your neighbor’s fence six feet away or 60 yards? All of these materials and design choices factor into the noise you hear inside and outside your home. This vast difference in building materials and radon system design is why the same fan can sound louder or quieter depending on the home it was installed upon. This is also why radon fan manufacturers do not publish sound data (or so one engineer told me off the record). It’s too unreliable because so much of fan noise depends on where the fan is placed.
Fun fact: at PDS, our KTA low voltage fan is sound checked by a human ear twice before we clear it for sale. This eliminates factory lemons and fans that don’t meet our standards for vibration.
Noise Factor: Inside vs Outside
Fan noise can typically be broken down into two categories. Inside noise and outside noise. The first question I ask homeowners is: “are your neighbors complaining about the fan or is it interfering with your sleep?”. Radon fan noise that is heard inside the home is most likely due to fan impeller vibrations reverberating through the walls of the home. This can be reduced by using vibration dampening materials. Fantech makes LDVI couplers which stand for “low durometer, vibration isolating”. Basically, they’re squishier than normal couplers and less vibration makes it to the studs of the home.
If your neighbors are complaining about the noise, or your radon fan is interfering with your outdoor activities then typically it’s an airflow noise. This falls into three categories: oversized radon fan (see above), radon fan bearings have failed, or just bad luck. Radon fan bearings are self lubricating but can dry out after a number of years (usually around the eight year mark). Reminder: always run your fan 24/7/365. Fans that turn on and off frequently fail much sooner than those that run and stay lubricated. When your bearings fail, you hear a high-pitched whine. This is a dead giveaway that your fan needs replacement. Please perform these maintenance steps anytime you change a fan. Lastly, bad luck. Sometimes you just need a big fan, or you can’t change your system design and your fan is just plain loud. For loud outside noise, try a radon muffler. Radon mufflers work a lot like car mufflers. They reduce the noise energy that makes it out the exhaust and hopefully keep some peace and quiet for you in your yard.
Noise factor: fan placement
Is your fan right next to your bedroom? Right next to your neighbor’s bedroom? A good radon mitigation contractor will avoid this by designing a system where the radon fan is on a southern exposure (for moisture reasons: see below) and away from windows and bedrooms. Better yet, a good builder will build the home radon ready so a small fan can be used and installed in a pre-plumbed attic stack.
Noise factor: water and ice
Does your radon fan sound like a blender on sunny winter days? Soil air is warm air and in the northern hemisphere this means that condensation will form inside your radon pipe. I call it the “reverse pop can effect” (or soda can if you will). In the winter months, this condensation can freeze. When the sun hits your PVC or gutter the ice will loosen and crash down on your fan impeller. This is why ice breaks and condensate bypasses are so helpful in extending your fan life. Water running through the fan constantly can dry out your bearings. See above for why that can lead to a noisy fan that needs replacing.
Noise factor: muffler or not?
It will usually pay to have a radon professional certified and trained in proper fan sizing and design inspect your system. Yes, it will cost money but anything worthwhile does. As noted above, being able to use a medium fan size versus the most powerful on the market can save four figures over the life of your system: often less than the cost of using the best pro versus the cheap, untrained one.
If you’ve truly done all you can to design around noise, then it may be time for a radon muffler. For 3” PVC systems try the Diamond Muffler. It can go inline lower on the exhaust or at the termination. HushVent is another good choice for the termination side. For 4” PVC we make our own in house. It’s over 6” wide. You do not want to inhibit airflow when using a muffler. If you reduce the airflow you can increase your radon level and sometimes increase your noise as well. Click the muffler image to the left to see all our muffler options, or type “muffler” in the search bar above.
Thank you for reading!
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