r/TinyHouses • u/Choice-Adagio-8376 • 12d ago
Anyone leave a dehumidifier running in an empty tiny house for weeks?
Hello all, so I built this 200-square-foot place in the mountains about a year ago and mostly use it on weekends. The first real rainy stretch exposed a humidity problem we hadn’t planned for. After a few wet days, the windows are covered in condensation in the morning, the baseboards feel damp, and the hygrometer stays somewhere in the high 60s or low 70s. We run the vent fan and wipe everything down while we’re there, but then the house might sit closed for another two or three weeks. Cracking a window hasn’t helped much when the air outside is just as wet. Leaving the place completely sealed obviously isn’t working either. Before buying anything, I always check these window seals, roof penetrations, and the areas around the baseboards. I don’t want to mistake a small leak for normal mountain humidity. Assuming the house itself is sound, I’m looking at compressor dehumidifiers with a drain hose. And this Aeocky Rhea-001 was on my shortlist because it can cycle around a set humidity instead of running constantly, and the hose can drain downhill without relying on the tank. The listing also says it remembers the previous setting after an outage, which sounds useful for a place that sits empty, although I’d like to know how reliably that works in real life. The other concern is temperature. The house can get pretty cool overnight when nobody is there, so consistent operation in cooler conditions matters more to me than the maximum amount of water it can pull on a warm day. I’m not trying to hold the place at exactly 50%. I just don’t want to come back after two rainy weeks and find it sealed up in the 70s again. Does anyone here leave a dehumidifier connected for weeks at a time? Where do you run the hose, and have you found a good way to prevent a clog or backup? I’m also curious whether you leave cabinets and interior doors open or use a separate humidity alarm while you’re away.
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u/No7an 12d ago
I own a home in Northern Minnesota that is unoccupied for much of the year. We run a dehumidifier continuously and monitor temperature and humidity via sensors in the house. The dehumidifier is attached to our WiFi and can be remote controlled.
Completely necessary outside of the deep winter months.
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u/Wizard-of-Odds 11d ago
so what i don't get is why everyone in this thread is only talking about saturation... like the % you can meter with a hygrometer is only your relative humidity and 50%=/=50% - for example 50% rH at 30°C is equivalent to 13g H2O/Kg air, 50% at 10°C would be 4g/kg. also really important are the dewpoints...
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u/MrScotchyScotch 10d ago edited 10d ago
If your coils are freezing up the temperature in the room may be too low (<65F), or you have the humidity level set too low (55% humidity is fine), or it's not stopping at the set level, or the filters aren't clean, or there isn't enough intake or exhaust space.
Another possibility is the space is too big and the unit is too small. Always size up to the biggest one you can afford; even if it's way bigger than you need, it will dehumidify much faster, leaving it off for longer. My Frigidaire 50pt works well for a 440sqft space.
You could try using an AC wall timer to cycle the unit on/off on a schedule (either analog or digital version).
The simplest thing to do for cabinets/doors is put in a passive dehumidifier, next simplest is to install small soffit vents, optionally with dust filters/covers inside.
For drainage, get an external condensate pump, connect it to the output of your dehumidifier, and run the condensate pump's hose wherever you want (a bathtub, sink, or outside). Size of pump is determined by vertical lift of water.
Ultimately the thing that's going to determine dehumidifying needs most is how well the home is sealed against moisture. Do you have properly installed moisture barriers? Is water getting trapped in/under the home? If moisture or water vapor gets in easily you're gonna need a beefy unit, and possibly a vent fan running occasionally (negative pressure, not open window).
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u/mopbuvket 8d ago
I have had the same 50qt ge dehumidifier running for 12 years solid. It cost me 110$ when Obama was president and it still runs strong. Its always had a hose to drain never used the tank unless the Teflon wears out on the threads and theres a drip. It runs in a building in the south.
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u/allquckedup 8d ago
I have had a dehumidifier running in my basement for the last 5 years. Yes I have a hose running to basement drain. I clean the filter on average about every year.
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u/crackup 12d ago
Damn, around my place it's never been under 70% humidity. Being in the house is causing the moisture right? If you get it down before you leave, it shouldn't get more humid if there's no one in the house? If you elevate it like place it on the kitchen bench then the hose can drain into the sink.
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u/AlmightyFruitcake 12d ago
Houses get humid and will go moldy with no one in it with no ac running, you must live in an incredibly dry climate.
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u/crackup 12d ago
The climate here is never under 70% humidity. Average is 82%. So for us, running dehumidifier to get it to 50% will only last until you open the doors and windows!
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u/eninety2 12d ago
I guarantee you your indoor humidity is not 82%, if it were then you’d have a big problem on your hands. Your AC is a dehumidifier, it just cools the air along the way. More than likely your indoor humidity is <45%. Most modern thermostats will have a reading for humidity. If it doesn’t, then you should really get one. Anything above 50% indoors and you’ll start growing mold in the walls.
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u/disneyworldwannabe 11d ago
Our house gets into the 70s during the summer if we don’t have the dehumidifier running. Can confirm mold will grow. It’s not fun.
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u/Infidel707 11d ago
I dunno, I've had my tiny in storage for 8 months and I worried about that, but it's been fine with just running the AC once a month to dehumidify it. Feels less muggy inside than out before turning the AC on. This is with dew points of 75-77F.
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u/AlmightyFruitcake 12d ago
Any unoccupied house without ac running needs a dehumidifier yes. Many millions of people leave dehumidifiers running in their basements and crawl spaces for the same reason. Vent fans are basically useless in wet weather as you already surmised so it’s probably best to leave the cabin sealed with the dehumidifier running 24/7. Temperature doesn’t affect it running only humidity and alot of people in tiny houses don’t need heat for mild cold temperatures because in a closed area dehumidifiers actually produce quite a bit of heat once the rooms humidity is 50.