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Cold Air Coming in Through the Bathroom Fan [FIXED]

It can be quite annoying to head to the bathroom on a frigid night only to have cold air greeting you through your bathroom fan. On a hot summer day, that cold air might be a welcome guest, but this can be an issue for those whose bathrooms feel like a freezer.

Cold air entering your home through a bathroom fan can leave you frustrated, uncomfortable, or can even cause illnesses. What is the root cause of this issue, and how can we get rid of it?

This article was created to help answer these questions by detailing all the reasons why cold air would be coming through your bathroom exhaust or extractor fan and includes all the information you’ll need to solve this problem.

bathroom fan

Why Is Cold Air Coming Through Your Bathroom Exhaust Fan

Issues with the Backdraft Damper

The most widespread cause of the cold air issue is problems with the backdraft damper. When installed in HVAC systems, backdraft dampers ensure that air flows only in one direction and prevent unwanted airflows.

Backdraft dampers may get damaged or rust with age, but usually, they have been installed poorly and leave gaps that allow cold air to pass through them and enter your home.

A malfunctioning damper can also contribute to a bathroom fan starting slowly.

Issues with Exhaust Hood or Sealed Door

On the opposite end of the backdraft damper, you have your exhaust, where the air from your bathroom leaves the house. Unfortunately, this is also where the cold air first enters your home.

There are many different exhaust hoods, but you will find yours outside on your roof or on an exterior wall. Your exhaust vent is meant to let your bathroom air out but may be experiencing issues that are letting more air inside.

Some exhaust vents have sealed doors that you can close during heavy wind conditions. But if your door does not seal properly, you will be left with the same issues.

Cold Pipes

Depending on how your home was built, you will likely have pipes running right alongside your exhaust vent. If the pipes get cold enough from the weather or excessive cold water use they can actually cause your exhaust vent to get cold as well.

If your exhaust vent gets extremely cold, it can turn air traveling through the vent from warm to frigid. Cold air is denser than warm air which makes it easier to seep through your exhaust fan cover and into your bathroom.

How to Stop Draft From the Bathroom Extractor Fan

Repairing or Replacing a Backdraft Damper

It’s pretty easy to check a backdraft damper. After removing the exhaust fans cover, you can inspect the damper with a flashlight. If the damper is loose with significant gaps, it will need to be replaced or reinstalled.

To get full access to your damper, you will need to remove both the exhaust fans cover and the fan itself, which usually only requires a screwdriver.

Your best option is likely to purchase a new double backdraft damper which is much more effective at keeping the cold air out of your bathroom.

Resolving Issues with an Exhaust Hood or Sealed Door

Inspecting your outdoor exhaust vent is as simple as walking outside if your vent is on a wall. However, if your vent is on the ceiling, you will need roof access to get to your vent.

Outdoor vents take more abuse than those protected inside your walls. As a result, you may notice visible damage that needs to be repaired, and you should inspect outdoor vents periodically. Depending on the damage, you may need to replace the vent entirely, but you can repair these vents in most cases.

If your vent has a sealed door, you should open and close it to make sure it’s working correctly and check the door itself for any damage.

Getting Rid of Cold Pipes

If your vent is not the issue, cold pipes are likely to blame. If you were to follow your exhaust vent and find no pipes running alongside it, then the vent itself is the cause of your problem. But it’s very common to run piping alongside vents.

Pipe insulation sleeves are an easy and effective way to get rid of cold pipes. You cut the sleeves to the size of your pipes and slide them over your piping. You can attach plastic ties or plumbers tape for extra stability.

Insulation sleeves not only help to keep cold air out of your bathroom but can also keep flowing water at the proper temperature and even prevent pipes from bursting.

Adam McCoy

Adam is an HVAC expert and the owner of Mackydo's HVAC Services with decades of experience in fixing and installing air conditioning units, furnaces, and every type of cooling and heating equipment you can think of.

Adam believes that your home is your sanctuary. He loves sharing advice based on his lifelong experience and treats every HVAC problem as if it was his own.

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At Loo Academy, our mission is to offer trusted advice for everything related to bathrooms (design ideas, plumbing advice, showering & bathing tips, remodeling guides, and more) — a place where we all spend a great deal of time.

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