There’s going to come a time when you have to replace a bathroom fan. They say nothing is certain but death and taxes, but I’d like to add a third: repairs! Repairs are inevitable. Just last week alone, three things broke down on us. When you’re a do-it-your-selfer and a blogger, you have to look on the bright side of things. It’s a good week when repairs alone give you a ton of things to write about!
I wasn’t sorry to see the old fan go. It was so loud and clunky; I could hear barely hear Hubs singing rubber ducky outside the bathroom door 🙂
Hot Air Rises!
As (bad) luck would have it, Hubs had to replace the bathroom fan during the hottest and most humid blast of weather. The attic was so hot, even his sweat was sweating. Not only did the bathroom fan stop working. Ironically, the same morning our air conditioner broke down too. So even though I didn’t break a sweat working on the fan, it sure felt like I did! Oh well, I guess our pain is your gain.
Personally, I would never want to attempt such a dirty, grimy job myself. But Hubs is a perfectionist and likes things done right. For instance, he’s going to seal and insulate all the duct work. When you hire a contractor, they’re in and out so fast. It leaves you wondering if they sealed things as thoroughly – if at all! You hear stories of contractors taking shortcuts. Like not bothering to connect the bathroom fan to the roof vent. This is a HUGE problem as mold will grow unless the fan is properly venting through the roof.
How to Replace a Bathroom Fan
So, is it hard to replace a bathroom fan? Not if you replace what’s already existing!
To start, hubs removed the old fan so he could find a replacement that would fit without having to cut a bigger hole into our drywall. He taped a plastic bag to the ceiling so he could cover up the hole after removing it (wouldn’t want any critters – or insulation – to fall into the bathroom, would we?).
He also protected all the surfaces in the bathroom by taping plastic to the walls and on the floor to catch any insulation/mess that might drop down when he was working in the attic later.
Inspect Before You Replace a Bathroom Fan
Then Hub inspected the condition of the old ducting in the attic and discovered two things. 1. Poor installation of the original 4″ pipe leaving plenty of gaps. And 2. the builder’s contractor cut too big a hole in the roof – leaving an even bigger gap.
Here’s what the old duct (and fan) looked like:
Because of the gaping hole in the roof, Hubs was going to have to use a 5″ gasket in order to bridge the gaps at the roof vent and then replace our 4″ ductwork with 5″ fittings instead.
Hubs found a specialty fan store that sells to the building industry, but is open to the public. He took the old fan with him. It cost him $75 for a new whisper quiet fan (only 1 sone). Consider any fan under 1.5 sones to be quiet, so keep that in mind when shopping.
Another thing to keep in mind is the diameter of the duct connector on the new housing. To maximize performance, try to match your duct diameter to the new fan. As I mentioned, our duct was originally 4″ wide but we needed 5″ to span the gap at the roof. So Hubs decided to buy a duct reducer (installing the 4″ end onto the fan and the 5″ end onto the new ductwork). There’s nothing wrong with increasing the size of the ductwork. But don’t ever do the opposite, or you will restrict the exhaust from the fan!
Replace a Bathroom Fan – Calculate CFM
With respect to performance, a fan’s ability to move air is measured in cubic feet per minute (CFM), so look for a CFM rating that will meet your needs by moving enough air for the size of your bathroom. To determine your CFM rating, use the following formula:
Length x width x height x .13 = the minimum CFM rating
In addition to the fan, Hubs purchased a variety of new fittings too. Get more than you think you need and return what you don’t use; there’s nothing worse than being stuck in the attic and then realizing that you have to run out to buy something you didn’t get!. All-in, it cost about $125 for the fan and supplies. It would cost you up to a couple hundred dollars more than that to have someone install it for you.
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Hubs cut the power to the bathroom so he could connect the wiring safely without risk of electrocution! He suited up in a white Tyvek suit, like the one pictured below, so he could protect himself and his clothes from the scratchy insulation. He also wore a mask just in case of mice, which almost always reside in the attic. You need to take the precaution of wearing a mask so you don’t breathe in any toxins.
Hubs placed a ladder beneath our attic access (ours is in the bedroom closet) and took all his equipment up with him in a box to keep it all together. This included a drill, screws, screw driver, tin snips, duct fittings, fan, electrical bushing, silver tuck tape, cord etc. He also took a bright light on an extension cord up with him so he could see (the light was run to another electrical power supply that was still working).
Hubs has previously done work in the attic so he had already placed some runner strips of plywood across the joists. You’ll need that so you can walk without accidentally falling through the drywall. Rip down a piece of plywood for this purpose if you don’t already have some in the attic. Once in the attic, push aside all the insulation to locate the electrical wiring and hole leading to the old bathroom fan
Install the New Fan
Position the new fan body over the hole in the ceiling. Attach into the joists with screws. A metal strip (shown below) attaches to the back to help secure it to the joist. Depending on where your hole is positioned between the joists, you may have to install anywhere from one to 4 of these strips. These can greatly reduce side to side vibration.
Our fan was positioned beside the joist so we only needed one new strip at the back:
Install the electrical bushing onto the fan (it protects the wire). Then feed the wire through and connect it.
Start dry fitting metal ducting. Hubs starts with the reducer first and continues until it all lines up with the roof vent.
As you can see below, one of the pieces of ducting articulates so it can be twisted into just about any position to line the ductwork up with the roof vent.
How to Seal the Gaps
Hubs used a 5″ gasket with a seal around it for the connection to the roof vent. This is a much better solution than the straight run with release cuts the builder previously installed because it seals any gaps. He had to use tin snips to fit the gasket flush against the joist in order to line it up with the roof vent. Once it fit, he peeled the tape off the gasket and pressed it up onto the underside of the roof. He pre-drilled and inserted screws all around the gasket as shown.
When all the ductwork was connected he pre-drilled holes into each duct joint and installed two 8 x 1/2″screws to hold the sections into position.
The Final Wrap Up!
The next step is to use silver tuck tape to seal along the edges of the fan. Wrap each joint all the way around with the tuck tape to seal it tight.
Before finishing, Hubs turned the power back on to make sure everything was running smoothly. Then he turned the power back off (as a precaution) and went back into the attic to wrap the pipe with insulation and tie it on with cord (reusing the original insulation). The last step is to return the blown-in insulation to its original position between the joists.
Bring all the tools back down and then put the ceiling cover over the fan to finish it off. Now the fan purrs like a kitten; bring on the rubber ducky!
I hope this guide gives you the confidence to replace a bathroom fan! The average fan only lasts about 10 years so that’s a lot of fans if you’re living in your ‘forever home’.
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