A few years back we did our primary bath. Well, to be more accurate – we put a quote, unquote primary bath into what was once an 8×8 closet. After a lot of consideration, we decided not to reconfigure the room, I mean – move walls or change the door’s location. We just put it in.

Closet turned Master Bath

We decided to hire this job out to my wife’s Other Man, you know – the “Other Man” … Mr. Pete, we’ll call him. He works with my wife as her partner on her flip projects. (Note: Number 3 is under way, but is moving slowly – thanks in part to an extremely uncooperative Winter.) Here’s a look at their last >> Mrs. Moxie Flips Out 2.

Not going too much more into it, I knew at the time of one area where we (*cough* the Other Man) skimped. For the connection on, the venting for, the new bath fan, he used flex duct, and dropped it into a corner of our attic. There it funneled into a strange apparatus that he … engineered.

Now, I knew, you should almost under no circumstance ever vent into an attic (not even into a vented soffit – like some builders are prone to do). I knew this … yet I did defer (for a couple reasons) to my wife’s partner; I let him have his way.

So … What happened?

Well, within a matter of months, we began to notice the formation of small spots on the bathroom ceiling. Yep, Mold!

While this was quickly wiped clean, I also made a quick visit to the attic, where I noticed that the … apparatus had come disconnected from the bath fan housing. (Essentially the bath fan blew it right off.)  At the time, I remember thinking – “I have got to address that bath fan venting, and get it vented properly, to the outside.”

That was probably somewhere around, January 2012. Ha!

mold spots on bath ceiling

And well, another year … and a half passed and in that time the mold spots returned and left, and then returned, this time – a little more pronounced. Areas of the ceiling too showed signs of puckering and the paint even began to flake and peel in some spots. Whoa! I can remember at the time saying, “Yes, I know Dear. I’m getting to it.”

Installing Bath Fan Venting in a Finished Attic Space

Rigid 4 Inch Duct for Bath Fan

I hope through my story I impress upon you the importance of proper bath ventilation. And yes, sure, your bath venting set-up can break down at many places. Mine – sure, insufficient venting, which was dumping moist air into an under-insulated attic above a ceiling constructed of plaster and lath.

Now, I know those may not have been the only factors coming into play here. The bath door, for example – did the installer (me) ensure that a minimum ¾ inch clearance was left to allow for the proper amount of make-up air? Yeah, you know – an old house and the floor at the door is slightly slanted, so just to be sure – I took another 3/8” off of it before I even started the work.

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space at bottom of bath door

Ensure a 3/4″ space for bath fan make up air

And anyway … I took a Sunday afternoon, and as our attic is a finish…able space, I hard-piped using 4” rigid duct, going out the attic’s side wall. It wasn’t a super-amazing or difficult project, considering of course that the bath fan had already been installed. But imagine it – a one man show up into the 3rd-floor attic, down to the ground and then up a 32’ ladder. Down the 32’ foot ladder and repeat until it is hooked up. A five-foot run of duct took roughly four hours (ugh!) and I see why now that the Other Man wanted to avoid it.

32 foot ladder bath fan venting

Other measures taken: Prior to touch up the service with some drywall compound, I used an over-the-counter moldicide (maybe I can call it that) to more permanently treat the ceiling, I primed with KILZ 2 and I painted using a Behr Kitchen and Bath paint. This Sateen finish – hopefully offering a more moisture-resistant sheen. (Like the Other Man who painted with a Flat … I simply grabbed what I had lying around.)  I added a Mildewcide Paint Additive before rolling it on.

mildewcide paint additive

And one final note: When choosing our bath fan, I selected a NuToneModel 684NT. It’s very much a budget model, sold exclusively at the Home Depot. Rated at 80cfm and up to 75sf, I figured it was enough to service this just smaller than 8×8, less than 64sf, space. (I chose the same model for our 5 x 12 hall bath, and installed it independent of this renovation (with proper venting) several years earlier.)

finished bath ceiling

If the mold and paint flaking in the end does not subside, I plan to upgrade this fan – a process which will unfortunately require an entirely new housing i.e. I can’t just slip in a new, beefier fan motor. Also, as I seem to constantly remind everyone in my household, there is one very important thing when it comes to bath ventilation – you have to, regardless of the sizing of your bath fan, actually run it when you shower. Thank you.


Disclaimer: This post was sponsored by no one, other than myself. While I am again humbled by a house, I share it to show what could happen if you don’t do things right the first time. I know too that I need work on not only my attic insulation (possibly insulating my new duct also), the paint in my gables, as well as also, Yes I know – I still need to stain my bathroom door. I swear I’m getting to it.

For more on Installing a Rigid Bath Fan Duct in 9 Steps (posted by me on the social media site – HomeTalk.com). For more Mold Prevention Tips, please see the article – Building for the Fungus Among Us.  :~)

Rigid Bath Fan Vent Installation Steps

For more on selecting a Bath Fan and how to vent it, here’s an article from HGTV – Choosing a Bath Ventilation Fan. ~ jb

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