Cheap DIY humidity control options?

I live in the Pacific North West where it rains. A lot. I literally live in a rain forest.

You would think that would mean high humidity all the time, but it really doesnt when it comes to growing. The outside air might be at 80-90% humidity in the summer after a rain, but when you warm that air up to 80F in a tent, the humidity drops like a rock. Right now, its raining and cold, and the humidity outside is only 37%. In the room where my tent is, its 70F and 46%. In my tent, its 81F and 38%.

Thats typical for me during veg or early in an auto run. Once the tent fills up, the humidity will get up to a better range. If its really full, the humidity can get too hi. Thats easily handled by running exhaust fans and inside fans, but its mostly too low.

Im trying to come up with better ways to increase the humidity early in a grow. Ive tried filling containers with water, and using paper towels to wick it up, but that does almost nothing.

So Im thinking of trying one of those cheap foggers.

Im just going to run it manually at first to see if it even does anything. I also want to be sure I dont end up soaking my lights, fans etc. 110 volts + water isnt a great idea.

If it looks like it might work, I thinking of using one of the Inkbird humidity controllers. It seems ot be the cheapest option that actually works half way decently.

Im still looking for one that isnt pre-wired in the hope that it will be cheaper. Im always on a tight budget! :slight_smile:

So, have any of you guys come up with a good way to increase humidity on a budget?


Pretty much the setup I was using. :+1::seedling:


Excellent! Do you have any issues?

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No, I use RO water, but have to clean the bucket pretty frequently, it gets slimy. I use this single disc humidifier here.


I use one of those, its great. Actually a couple. One runs my dry/cure box, the other the flower room. Using them for years with no problems.


Building a humidor/drying chamber.
Got some of these on the way. Might be useful and cheap in your application.
Relay will work in any size grow but you are likely to need a bigger ultrasonic mist head than mine.


Get a mylar blanket and create a survivalist atmospheric dew condenser in the space. You need to create a temperature variance between the underside of the blanket and the top to catch ambient moisture, mostly from soil evaporation.

If you’d like more info or how to automate utilizing ambient h2o this way please DM me


Thanks, I had forgotten you posted that in another thread. I should probably break out my RO filter again for this. My water has a fair amount of minerals in it - well water.


Yeah, I think that mister would be too small for my space. I like the price on the other items, but they all ship from china with long waits.

I found this one on E-bay. It can be here by next week. I think I will give it a try.

Thanks for the suggestion! I am familiar with that trick, but it wont work for me - there is no soil anywhere in my tent. I grow aeroponically. My seedlings start out in a 3" net pot that sits in a hole cut into the bottom of my tent - which is a sheet of 1" thick foam. I use no medium in the net pots either, so there is no source of moisture in the form of evaporation. Late in the grow there is enough transpiration to raise the humidity all on its own, but not when the babies are young.

This is how the babies typically look when first put in the aero system.

The roots hang down below, and grow in a 58 gallon fabric root chamber that is kept at 69-70F and air atomizing nozzles fill the space with 50 micron sized droplets.

Later on they get big and can fill the entire chamber on a long grow.

No soil anywhere :slight_smile:


Now that is some root porn there.

Cheers Johnny


Mambru, aeroponics is THE optimum way to collect dew. Add an extra spray nozzle but run it into the tent instead of in the root containment unit, then cut the power of the nozzle to 10-25% power of the others, maybe even timer the sucker so it sprays into the microclimate intermittently.
AH! Rig this hose to a humidity sensor and tie a reading of less than (your humidity goal) to the power switch for just that nozzle; if humidity < x then power on mister.
How bout it?

Hell, even I wanna build it now. I love programming algorithms into simple af electronics


I considered that, but the nozzles Im using make droplets that are way to large to safely, or eficiently spray into the tent.

Those ultrasonic misters generate droplets smaller than 5 microns. My nozzles make droplets between about 20 micros to probably around 100 microns. Most of the water volume will be in the larger droplets. Its the difference between fog and light rain. My nozzles wont increase the humidity as much as they will just get everything wet.

Just to compare, a 20 micron droplet holds about 4^3 times as much water or 64 times as much water as a 5 micron droplet. A 100 micron droplet holds 20^3 or 8000 times as much water. In other words, a single 100 micron droplet holds the same amount of water as 8000 5 micron droplets. The volume of a sphere varies as the cube of the diameter. Double the diameter and you get 2x2x2= 8 times the volume.

Some of the issues is that those relatively large droplets can cause more issues with electronics and they form larger droplets on leaves - which will burn the leaves when the lights are on. But they are also slower to evaporate. The smaller droplets will turn into actual water vapor much faster then the larger ones. Which in turn means the humidity will go up much faster with less water put into the tent. It also means that the mist can evaporate before it gets everything wet - I hope.


Use a bucket of water put a rowelin it draped over er out over thevside hanging down as a wick and put a small fan blowing on it im pretty sure that will increase the humidity


You win, bud. Not like “nozzle” was a catch-all phrase for something creating a small amount of sub micron sized droplets.
You basically told me I was wrong, and then said the only thing wrong with the plan was the nozzle and droplet sizes.
Can’t let a guy have one can ya?

That does work, and I have tried it, but it is slow and doesnt raise it high enough. I used paper towels because they get covered in algae - as does the container. Thats why Im looking for a faster technique that can be regulated.

I do apologize if that came across the wrong way. It was not my intention to offend you. I have a very bad habit of nit-picking, getting lost in the details, and coming across like a pedantic, know-it-all ass. As my wife reminds me quite often, it is very irritating. Sorry!

I was simply trying to say that the nozzles I have on hand wont work. You are quite correct that there are nozzles, and delivery systems available that would put out much more suitable droplet sizes. If you are considering trying that technique, I can make some recommendations and point you to some suppliers. I have been researching nozzles intensively for a while now. Which system would work best will depend to some degree on the size of your grow space. For smaller volumes - like most grow tents - very high pressure hydrolic nozzles would be better I think, but for larger spaces - like a full size room - then air atomizing nozzles will probably work best.

Again, I apologize for coming across like an ass.


I once added a tube of chicken wire onto my intake. I then proceeded to wrap a wet towel around this tube. Bought me 10% but needs to be checked occasionally

I did this for a drying chamber that was too dry


In the case of seedlings and cuttings… domes are very helpful.

For rooms or tents there are humidifiers that work and have built in controls. I purchased a room humidifier used for about 20 bucks…new filters (2 sets for $20) bought a room thermometer (digital) with RH indicator and adjusted the humidifier for what I wanted.

Some other good suggestions here too. both the buckets and the nozzles.


Thats an interesting idea. It would also cool the intake air as it drew in the moisture. There are times when that would come in handy for me - especially growing in the summer. I dont have any fans with enough suction to make that work, but I may give that a try next summer.

Another idea just occurred to me. I have to give a nod to @Iamthecheesegodz because that would be an excellent application for one of my existing nozzles on a timer. It could be placed inside the fabric wrapped chicken wire and used to keep the fabric wet. Not sure where I could make the space for it, but Im liking the possibilities.

Yeah, domes are great for seedlings.

I originally was wanting to do exactly that. I have been checking Craig’s List periodically for humidifiers, but the only ones that showed up anywhere near me were all way too big to fit in my small tent. A friend of a friend was going to give me one, but it was huge. It would have taken up 1/4 of the floor space in my tent. I like free but I just couldnt figure a good way to make that work :slight_smile:


That ultrasonic fogger I linked above arrived today. I tried it out, and it doesnt make nearly as much fog as I was picturing.

I made up a crude float - I would recommend buying one pre-made unless you like ugly. Im not showing mine. :slight_smile: I put the float and gizmo in a 1 gallon bucket with RO water in it. I also rigged a small 2" computer fan on the side of the bucket blowing across the bucket. The mist visibly travels at least 12"-18" before it fades out. I have a fan in the top of the tent that runs 24/7, so I may not need the computer fan.

My tent is currently at 37% humidity and 80F. We will see how much it raises the humidity. I’ll check every few minutes.

Once I see if this raises the humidity, I will test water consumption. Oh - I had to rig a splash guard to keep the thing from splashing water all over the place. It shoots large drops 3" to 4" above the resonator element.

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If the tent is ina seperat room in your house put it outside the tent and blow air into the tent

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If you mean the full size humidifier, I have even less room outside my tent. I grow in my hobby room. I say “my” hobby room, but it doubles as my wifes junk room, and my computer room. I quite literally have zero floor or counter space outside the tent. I have to move stuff around to do any actual building :slight_smile:

Up-date on the fogger. It works - BUT - only if the exhaust fans are off and the internal circulating fan is off.

Takes it about 20-30 minutes to go from 37% to 56% - which seems to be the upper limit even with all fans off. Not sure this is going to work - especially during hot days when the exhaust fans have to run to keep the tent temps under control. When that fan kicks on, the level drops like a rock, then takes quite a while to build back up.

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