The most common reason for the bathroom exhaust fan to make a weird noise is when the fan system has – built dirt over time, fault in components, loose parts, alignment issues, etc. These are normal to hear if your fan is under running condition.
However, it becomes surprising when you hear your exhaust fan making noises when it is off. Imagine going to your bathroom and suddenly hearing squeaking or banging noises. What would be your reaction to such a situation?
At first, I was scared to hear those weird noises as we generally do not expect our exhaust fan to make noise when it’s off. But after taking a closer look, I finally figured out why a bathroom exhaust fan can make noise even when it’s off? Here’s why:
Most probably, the wind blowing outside must be hitting the vent’s flapper, causing the flapper to strike on a metal-to-metal surface. Besides, bathroom fans in condos are connected with a single exhaust fan duct, so when your neighbor turns on their exhaust fan, you hear a low buzzing noise coming out even if your exhaust fan is off.
That was in a nutshell. Let’s break it down for more clarity.
Why Exhaust Fan Make Noise Even When Off? (Explained)
Condos Use Single Exhaust Duct
If you’re a condominium dweller (living in an apartment), the most probable reason for hearing low buzzing noise from your exhaust fan when it is off is the connection of bathroom fans to a single exhaust duct. What exactly this means?
In this type of vent system, a single exhaust fan is located centrally, running on the same duct. Ducts are generally the tubes in HVAC to deliver and extract exhaust air. Therefore, whenever your neighbor turns on their exhaust fan, the noise travels through the single connected duct. As a result, you hear a low buzzing noise.
Flapper Noise Due to Wind
If it’s windy outside, you might hear some banging noises coming from your exhaust fan when it’s off. What mainly causes this is the ‘vent flappers,’ also known as backdraft dampers.
It is common for a vent system to use a flapper, preventing outside air from entering. Spring-loaded or weighted flappers are usually used in the vent system, which gets easily picked up by the wind and drops down, causing your exhaust fan to make a banging noise when off.
As you’ve got an idea about causes, let’s look at some of the possible fixes for a bathroom exhaust fan making noise even when off.
3 Effective Fixes On Bathroom Exhaust Fan Making Noise When Off
Add Soft Foam Around Exhaust Hood
Placing a sound-absorbing material between the flapper and exhaust fan’s hood can eliminate the noise coming. The best solution for this is to add soft foam to the exhaust fan’s hood so that whenever the wind lifts and hits the metal, it won’t make any noise.
These foams allow air to travel through the openings, absorbing the noise produced by the strike. I recommend getting this weather-stripping foam tape as it won’t come off so easily due to its strong adhesive backing and waterproofing property to survive any season.
Note: After applying the foam, verify whether the flap disk closes without leaving any gap. Otherwise, air, birds, and rodents can enter through the gap.
Add Some Weight On Flapper
Another commonly recommended method is adding weights on the flapper. Weighted flappers get difficult for the wind to lift the flap disk up and down, preventing it from making banging noises.
You can achieve this by simply sticking adhesive-backed wheel weights to the flapper’s disk. However, keep in mind that getting the flapper overweight will stop the flapper from opening when your exhaust fan turns on. What you should do then?
I recommend placing a 1/4-oz wheel weight first to check how well it works. If the weight is stopping the wind from lifting the flapper disk at the same time allowing the fan to lift an extent, then go with that setup.
Otherwise, place on another weight and verify the same again.
Replace the Existing Flapper/Damper
The old school bathroom damper (known as gravity flapper) is popular among people, but it lacks in stopping the wind from lifting the flap disk. Therefore, you need a better solution.
If you ever plan to remodel your bathroom or just want to change the existing flapper, one of the best solutions is to replace it with a spring-loaded butterfly backdraft damper.
What’s special about it?
A backdraft damper prevents noise problems because it has a rubber gasket inside that seals the air when the flapper closes, maintaining an airtight seal. Most manufacturers use rubber seals that stop air from entering your home and prevent noise leaks. Not only known for eliminating noise but also allows the air to flow in a single direction.
- Recommended: AC Infinity Backdraft Damper
Get Idea On Back Draft Damper Installation
Note: Get A appropriately sized backdraft damper that fits your air ducts. Take the help of experts if you have no idea about sizing or installation.
See Also: Ultimate Backdraft Damper Guide
Summing everything up, the reason behind noise coming from the exhaust fan even when off could be either gravity flappers getting lifted by the wind, causing it to hit the surface. Or it’s due to a single exhaust fan duct shared by your neighbors.
If you’re living in a condo (apartment), It is strictly recommended not to make any changes with proper permissions. You need to contact your condo management company (if any) to provide an effective solution. Other than that single-family homeowners can try those effective methods discussed above.