Shower-drying portable fan?

One of the things we got right in the remodel is our nifty walk-in shower. It's luxurious and awesome.

BUT...

Despite running the bath exhaust long and consistently, we get some mildew/mold on the grout.

If I could imagine the perfect ad-hoc solution (because the crazy stuff that exists for Proper solutions are untenable) it would be a battery powered blower with a timer on it. So after a shower, you'd set the freshly charged fan in the shower and let it dry the floor and walls while the exhaust fan was whisking that airborne moisture outside

I'm not finding much in the way of fans that fit that description. I'm almost wondering whether I should get one of the Milwaukee fans that uses my M18 batteries and just let it run til it shuts down (unless someone happens to notice it's dry).

Anybody seen such a fan, or have a better solution?

It'll ruin your battery to run it until it's dead 

Something like this?

Floating Doc (Forum Supporter) said:

It'll ruin your battery to run it until it's dead

Modern stuff is too smart to do that. It's an actual Milwaukee fan, so it doesn't run to "dead" so much as "sensible battery level for shutdown."

EDIT: By "actual Milwaukee fan" I just mean it's not some random piece of junk that happens to accept the M18 battery, but something of enough quality to have sane battery protection.

Just because I hate to say stuff like that and then turn out to be too sure, I checked the manual:

Milwaukee sayeth:

To protect the life of the battery pack, the fan will
shut off when the battery’s charge becomes too
low. If this happens, remove the battery pack and
charge it according to the charger’s instructions.

Actually, given that it'll run 17 hours on the low setting, we might be able to just turn it back off later without undue hovering...

In reply to 1988RedT2 :

Pretty much, but I need an unattended version.

Slugs eat mold 

In reply to mdshaw :

What's the rest of the new shower ecosystem? Birds for the slugs? We've already got cats, so maybe that'll cap the bird population?

I have the bath fan (located in the shower) on a timer/humidity sensing switch (outside the shower), but found that the trick to getting the shower to dry was propping the door open to let air circulate with the fan set to run 30 minutes.

I just hang a hand towel on the shower door handle and tuck it into the door opening to leave a gap (1") to allow air to enter from the bottom as well as the top. 

First... assuming you have a glass door?  Or a curtain.  Either way... adjust this advice as needed.

I solved my issue by doing three things: 

- Real, honest money spent on a good, high-flowing (and quiet) exhaust fan really does make a difference.  I was also sure to install it kind of half in and half out of the shower.
- I cut off the bottom inch or so of my bathroom door, but I have also installed a vent in the lower part of a bathroom door before with good success.
- I keep a bottle of that "after shower" tilex or lysol stuff.  I'm convinced it's just a watered-down version of the same antibacterial cleaner you buy for kitchen counters and bathroom tile, but it just takes a couple squirts and everything kind of sheets off and I haven't scrubbed mold for years.  It also makes scrubbing the shower a less-frequent and less-intense ordeal.

Is there some means of leaving the shower door open a hair?  My old house had a little flip-out stop that held the door open about 1".  I think that made a huge difference.  My F-I-L swore by keeping a shower squeegee and doing a quick wipe-off of the walls and glass.  He figured the more he got down to the basin and down the drain, the faster it would dry.  That was always a bit too much work for me.

The other thing that convinces me it's an airflow issue (or at least that it helps) was that I switched my curtains away from vinyl.  The outer curtain is a waffle-weave cotton and the inner is a woven poly or something.  It isn't water proof, but it stops any spray from making it out.  I think my dry times dropped significantly when I went that route.  I used to replace vinyl liners every year because they would start to mildew at the bottoms, but this woven liner has never mildewed.  I just wash it in the laundry a few times a year.  Again, I know you might not have a curtain, just pointing out the fact that I think airflow is huge.

I have heard good things about that "after shower" stuff.  I think my Dad uses it.

I agree about airflow, but unfortunately I'm down to where I'm asking about fans to set in the shower. Let me elaborate...

I don't know the make/model of our exhaust fan, but we had a very sane contractor and we didn't tend toward skimping. It's nice and quiet but clearly running.

We do tend to leave the bathroom door ajar, so it's not that it's not drawing (drier) air from the rest of the house.

We were advised to squeegee the glass wall to keep it nice, and have expanded to squeegeeing more and more in an attempt to get things to dry out, but yeah, I'm running out of patience for squeegeeing the walls and then trying to coax the water down the drain (yes, the floor slopes to the drain, of course, but not so steeply that all the water shoots right out).

Curtis, I think you're on the money on airflow; we don't have a door or curtain; it's quite open, and while the fan isn't half in the shower, it's fairly close to the shower and the separating wall doesn't run to the ceiling. Er, a picture's worth a thousand words:

And that's sort of how I wound up here asking about fans to set in there to get more evaporative drying. It sounds like we're really covering all the other bases already, so at least trying to improve this aspect doesn't sound like we're missing a bunch of low-hanging fruit.

How often do you use the tub? My suspicion is rarely. If so, set a dehumidifier in the tub and set it so the water captured can just run down the tub drain.   You could make this the driest (air) room in the house if you want.   Or, a dehumidifier anywhere else in the bathroom. 

If the mold is primarily on the grout have you tried a grout sealer?

I typed 'clip on fan' into Amazon and got a bunch of results, both battery operated and 120vac.  Maybe one of these, clipped to the top or edge of the shower door would work.  If you want to run for a specific time period and then turn off, a 120vac fan with a simple timer plugged into the wall is probably easiest, but something like this one that is supposed to run for up to 20 hours on a battery is another possibility.  https://www.amazon.com/GagetElec-Stroller-10000mAh-Rechargeable-Circulating/dp/B093F68NM6/ref=sr_1_12?keywords=clip%2Bon%2Bfan&qid=1652100810&sr=8-12&th=1

Where is the mold forming?  on the shower floor?

Are your sure that ceiling fan is installed properly/not clogged?  I'd get up in the attic / on the outside of the house and check the airflow first.  I dealt with a fan like that before in a rental property - the circular duct running to the soffit wasn't connected properly and was restricting flow.

Interestingly I almost never use the fan at all in my house and have no issues.

Your climate shouldn't be a factor in much of this.  You get less rain and fewer days of rain than I do here in PA.  I also would expect my 1900-built house to be a nightmare with mold because of my crawlspace and partial dirt floor basement.  It's always a bit moldy down there even though I run a dehumidifier 365 days a year.

Possible you're getting a source of mold in your house you haven't found?

I just hate to see you stressing over manually controlling mold every time you shower with fans or dehumidifiers when it seems like you're doing things right.

I feel like we're leaving the hood unlatched to solve an overheating issue when the answer might just be low coolant, if you catch my metaphor.  I'm not convinced that the issue stems from a lack of something in the bathroom.

Im in Florida. Everything molds. Bleach is your friend. Clorox toilet bowl cleaner with the angled tip is good for target application. In your situation you might try the toilet bowl bleach and then see how long it takes for the mold to come back. It's possible you aren't killing it completely when you clean so it doesn't take much moisture/growth for it to be visible again.

Do you have a smart thermostat? If not do you want one? If so, are there remote sensors that sense temperature and humidity. I don't know for sure, but would make sense for you to be able to trigger your choice of AC/heat/fan fan whenever the humidity of a sensor goes above presets. A central unit certainly empties a room sooner than an exhaust fan, and emptying all the humid air out of the bathroom should help with drying time.

ProDarwin said:

Where is the mold forming?  on the shower floor?

 

Are your sure that ceiling fan is installed properly/not clogged?  I'd get up in the attic / on the outside of the house and check the airflow first.  I dealt with a fan like that before in a rental property - the circular duct running to the soffit wasn't connected properly and was restricting flow.

Interestingly I almost never use the fan at all in my house and have no issues.

I am with Pro on this.  Make sure that the existing vent is actually working properly. 

Most bathroom vents suck (or don't suck).  You really need a good one to get air changes.  Many I have seen don't have any kind of enclosure around the fan and as such, they just spin the air around in the unit and move very little.  Many of these don't generate any kind of pressure so if you have a minor obstruction or it is trying to push the air any kind of distance they will not do it.  We spec the centrifugal-type fans to clients.  With these types of fans you can do a complete air exchange in a bathroom in minutes.  They are not cheep but they work exceptionally well.  This combined with a bigger gap at the bottom of the bathroom door should take care of things.  

You can wire these fans up to wall switches that have preset timers on them.  Like this:

This works well and lets you control the fan separately from the lights.

No one has mentioned the humidity. 
 

Moving air is not enough. If the fan is pulling air in with a similar moisture content as the air you are trying to exhaust, it will not dry the area. Ever.  No matter how long you run it. 
 

The theory of a bath fan (that's working properly) is that the bathroom is extra humid from the shower, and the air that is being pulled into the room is coming under the door from conditioned space which is less humid.  The greater the delta, the quicker it dries.

Where is the make-up air coming from?  Is it significantly less humid than the bathroom air?  If not, a fan won't help, even if it's moving 10,000 CFMs. 

It's very possible you need a dehumidifier, not a fan. 

If the rest of your house is as humid as the bathroom post shower, you have mega problems.  You'd also likely have mold growing all over the place, not just in the shower.

In reply to ProDarwin :

Not necessarily. 
 

He lives in the Pacific Northwest. Very humid. If his house has no AC, it's possible the humidity level is high enough to be a problem. 
 

Plus, if the fan is short cycling, it might not be pulling air from the corners of that shower

In reply to Jesse Ransom :

That bathroom looks big. Do you know the CFMs of that fan?

If it's a builder special, it's not big enough. 

In reply to Jesse Ransom :

Nice bathroom. 

SV reX said:

In reply to ProDarwin :

Not necessarily. 
 

He lives in the Pacific Northwest. Very humid. If his house has no AC, it's possible the humidity level is high enough to be a problem. 
 

Plus, if the fan is short cycling, it might not be pulling air from the corners of that shower

My point was that problem would be present in many places.  I would hope he has conditioned air of some sort.

Totally agreed on the short cycling.  It would be very easy for that fan (and most bathroom fans really) to pull in air without really removing air from that area of the shower.  They rely entirely on convection of that movement to "mix" the air in the room.  That's what OP is trying to accelerate with the portable fan.  It would be great if there were a way to do that without the hassle.

I think Mr. Joshua's suggestion of using your central unit to cycle the air is a good one.  Its a shame those things are energy hogs and there is no button to hit after the shower to make that fan run for 5 mins.  If you can use a remote humidity sensor to trigger it that would be a pretty simple solution though.