Keeping mold away from your shower - my favorite lazy hack

Totally agree - vent path is such an underrated detail. I’ve seen gorgeous bathrooms with fancy fans, but the vent just dumps air into the attic... not great for mold. Ever tried those humidity-sensing switches? Curious if they actually help or just another gadget to break.

I actually put in a humidity-sensing switch last year, mostly because I kept forgetting to run the fan long enough after showers. Honestly, it’s been pretty solid - kicks on when the room gets steamy and shuts itself off later. I was worried it’d be one more thing to go wrong, but so far it’s been reliable. Only downside: sometimes it’ll turn on if I’m just ironing in there or something weird, but that’s a small tradeoff for not dealing with mildew. Anyone else notice they’re super sensitive sometimes?

Humidity sensors are a wild ride, honestly. I put one in our upstairs bath (the one with the clawfoot tub and the world’s slowest window crank) because I got tired of playing “did I remember to run the fan?” roulette. It’s been a game-changer for keeping the old plaster from getting that musty smell, but I totally get what you mean about the sensitivity. Mine seems to think steam from a cup of tea is a five-alarm emergency - never mind an actual shower.

I’ve also noticed it’ll kick on if I’m just running hot water to wash my hands, which is kind of overkill. But I guess I’d rather have it err on the side of caution than let the walls start growing their own ecosystem. Still, sometimes I wonder if there’s a way to tweak the sensitivity a bit? Or maybe it’s just the price of living in a house where nothing is ever quite square and every project turns into a treasure hunt for the right screwdriver.

Curious if anyone’s tried those timers you can set for a certain number of minutes instead? I thought about it, but I’m so scatterbrained I’d probably forget to hit the button half the time. The sensor at least takes the decision out of my hands, even if it does get a little dramatic about humidity.

Funny thing - my neighbor swears by just leaving the window cracked, but in February that’s basically an invitation for frostbite. I’ll take a jumpy sensor over frozen toes any day.

You’re definitely not alone - those sensors can be a little overzealous. From a maintenance and property value standpoint, though, you’re making a smart call. A little extra fan time is way cheaper than dealing with mold remediation or repairs to old plaster.

- I’ve run into the same thing with humidity sensors in rental units. They tend to err on the side of caution, which is good for asset protection, but sometimes annoying for day-to-day living.
- Timers are great in theory, but in practice…yeah, most folks forget to use them, or they just don’t run long enough after a steamy shower.
- As for tweaking sensitivity, some models do have adjustable thresholds. If yours doesn’t, it might be worth swapping it out for one that does next time you’re elbow-deep in “why won’t this fit?” mode.
- That window trick is classic, but like you said - nobody wants to freeze just to keep the walls dry.

Honestly, a slightly dramatic sensor is probably the lesser evil. At least you know your plaster’s protected and you’re not getting surprise science experiments growing behind the paint.

Not sure I’d call a “slightly dramatic sensor” the lesser evil in every case. I get the argument - mold is a nightmare, and you don’t want to risk it, especially with old plaster or in rentals where you can’t always trust tenants to ventilate properly. Still, I’ve seen a few situations where overactive humidity sensors actually create their own set of headaches.

For one, if your fan’s running nonstop or kicking on at the slightest hint of steam, you’re pulling a lot of conditioned air out of the house. That means your HVAC is working overtime, especially in winter or summer. I’ve had clients complain about drafty bathrooms and higher energy bills, and when we traced it back, it was almost always an aggressive sensor or a fan that was oversized for the space.

“A little extra fan time is way cheaper than dealing with mold remediation or repairs to old plaster.”

That’s true up to a point, but there’s a balance. If you’re running the fan for 45 minutes after every shower because the sensor won’t shut off, you’re probably overcorrecting. In my experience, a properly sized fan (CFM matched to room volume), paired with a sensor that’s calibrated for your climate and usage habits, works best. Some of the newer models let you set both humidity threshold *and* minimum run time, which is honestly worth the extra install effort.

Timers do get ignored, but I’ve seen good results with fans wired to the light switch - fan comes on automatically when you turn on the lights, then stays on for a preset period after. Not perfect, but it takes human error out of the equation.

And yeah, nobody wants to crack a window in January just to keep tile grout happy... but sometimes old-school solutions still have their place if you can’t get the tech dialed in.

Long story short: dramatic sensors aren’t always the lesser evil. Sometimes they’re just trading one problem for another. Worth looking at all the variables before settling for “good enough.”