Every summer I get the same call. A rig sat in storage — sometimes only two or three months — and the owner opens the door to a wall of musty air, black specks on the ceiling fabric, and cushions that feel damp when nothing was ever spilled on them. That's Florida storage mold. It doesn't need long, and it doesn't need a leak. It needs moisture, something organic to eat, and still air. A closed-up RV in July hands it all three on a platter.
The number to beat: under 60%
The EPA's guidance on mold is blunt and useful: keep indoor humidity below 60 percent, ideally 30 to 50. Above 60, mold can start growing on any organic surface within 24 to 48 hours. Your rig's interior is basically a box of organic surfaces — wood, fabric, paper, carpet backing. And Florida outdoor air sits at 80, 90 percent humidity for months at a time. So a closed RV in storage doesn't have a small moisture problem. It has a Florida problem.
First: no gear fixes a leak
Before you buy a single absorber, find and fix the water entry. Mold is a moisture problem, and moisture almost always has a source — a tired roof seam, a wiper seal that's gone flat, a window frame that weeps. I've seen owners run dehumidifiers for months while a slow roof leak kept feeding the whole setup. You can dry the air all you want; if water is still getting in, you're just making expensive ice water.
If you have shore power: run a real dehumidifier
This is the only approach I'd call bulletproof down here. Put a 30-pint-class compressor dehumidifier in the shower or the kitchen sink, run a hose so it gravity-drains straight down the drain, and set it to hold about 50 percent. No pump needed if the drain is downhill — and if the unit ever malfunctions, the overflow goes down a drain instead of across your galley floor. Once the initial moisture load is out of the rig, the output slows to a trickle. Add a small fan on low to keep air moving, because a dehumidifier in a still rig just dehumidifies one corner.
If you don't have power: vents plus absorbers
No power means you work with airflow and chemistry. Crack the roof vents about a half inch — vent covers earn their keep here, since they let you keep the vents open through the afternoon rain. Then distribute passive absorbers instead of clustering them: front, middle, and rear of the rig, because one bucket in the middle of a 30-footer does almost nothing for the rear bath. I like the DampRid Hi-Capacity Moisture Absorber buckets — each tub keeps pulling for months — but set every one on a tray. The brine they collect is corrosive, and it doesn't dry itself back out. For closets and cabinets, little renewable silica units like the Eva-Dry E-333 hang on a hook and recharge in an outlet on your next visit.
As an Amazon Associate I earn from qualifying purchases.
Be honest with yourself about this approach: passive absorbers alone will not hold a stored rig near 50 percent through a Florida summer. This is a backup strategy that buys you time between visits — not a set-and-forget plan.
Open the cavities mold loves
Mold starts in the closed places: wardrobes, under-bed storage, overhead cabinets, the dead corners of the basement. Prop every cabinet and closet door open before you walk away — a folded piece of cardboard or a chunk of foam in the door frame is enough. An unventilated cabinet in a stored Florida rig is a petri dish with a door.
Measure it, don't guess it
Leave a cheap hygrometer inside so the humidity number means something when you come back. If you won't visit for months, get one with a remote sensor — a saturated absorber is invisible from the driveway, and the first sign of failure is usually the smell. By that point you're doing a mold cleanup instead of a storage check.
The day-one routine
What you do when you close the rig up matters as much as the gear. Open everything — vents, windows, cabinets — and let it air out before you lock it. Pull anything that holds moisture: the damp towels, the bedding from your last night in it, the paper products. And don't run a propane heater in a stored rig "for warmth." Propane combustion puts water into the air as it burns — you'd be humidifying the thing you're trying to keep dry.
Mistakes I keep seeing
- Absorber-only storage plans in real Florida humidity, with nobody checking between visits.
- Sealing the rig up airtight "to keep the humidity out" — you're trapping the moisture that's already in there.
- Ignoring a slow leak and blaming the weather for the musty smell.
- No hygrometer, no vent covers, no plan — just hope and a closed door.
- A plastic tarp over the whole rig instead of a breathable cover. You've just built a greenhouse.
Mold in a stored RV is a solved problem. Keep the water out, keep the air moving, keep the humidity under 60, and check on the thing. Nobody has ever called me in August to complain that their dry rig didn't have enough mold.
Learn it once. Fix it right.
I'm building a full RV structural repair course — slide-outs, roofs, water damage — filmed on real jobs, ugly parts included. Join the launch list and you'll hear about it first.