HELP! raise humidity in grow tent

[TheGoodFarmer]

I can't seem to get the humidity level in my grow tent to stay above 50% I am using an ultrasonic humidifier and can only get it to 41%. I am running two 150w hps, with an exhaust fan under 200cmf. Also my tent is only 2-4ft. How do you all handle this?

[Qwertywill]

A wet towel could be a potential solution, or a bucket of water

[Weed Pharma]

TheGoodFarmer, add an airstone to the bucket option

[TheGoodFarmer]

ok, ill try that. Thanks

[Toker1]

Swamp cooler located outside of the tent (so fans pull moist air in).

[Weed Pharma]

I wouldn't concern myself with 41% humidity at all- rooted plants will make up for it in water consumption-
Adjusting the nutrients (lower) to account for the increased transpiration, is the only thing you may want to do.
Most of my grows are done @ 30% rh.

[Colombo]

Considering I also run a 41% it is due to my forced hot air heating system! The humidifier unit lasts about a year and its not worth changing. Raising temp sometimes raises humidity based on your watering. If you can put a humidifier in the room your tent/ grow structure is. This will raise the room Humidity (long term solution) which in turn will raise the humidity in the air intake. An open pale of hot water also does the trick (short term solution)

[Greenpassion]

Heads up to all of you guys about humidity. House of Hydro. Google it. I don't have a tent, I have two rooms - but they have units small enough for tents. They are Foggers. I repeat Foggers. Foggers put humidified air into the grow area and they come, if you order it with a humidistat that can actually judge whatever you said it at. So I set mine at 56 humidity in my veg room, and 45 percent in my 12:12 room. And it keeps it there consistently without a worry. You can get one head, 2 head,3, 6 or 12 head or whatever number of heads you need for whatever size space you need humidified. I was actually able to speak with the person who work there and they want to know exactly the size space I had and what was going on, to determine what I would need. It is perfect. I had the worst problem in my house upstairs with my 2 grow rooms here in Vermont. And I bought two $10 plastic bins, some PCV pipe, and I went to House of hydro online, and for each room I got an eight head fogger and a humidistats , and now all is well in Oz.! I can't stress it enough. Never mind these silly humidifiers , towels hanging and all of that other stuff. I had tried it all before this and I am so happy I made this change. Believe it.

[Qwertywill]

While yes foggers do work, so do humidifiers, wet towels etc. They all put humidity into the air.

The reason why I suggested mine were cost. Not everyone has money they can drop short term.

A humidifier is the best way to go however.

[Greenpassion]

True. Humidifiers would do the job in a tent. In large rooms it's a different story.

[Toker1]

Three words: portable swamp coolers....hooks up to a hose for continuous flow (Or just refill a reservoir if desired).
Small pump with low flow/vol. for affordable operation costs. Hooked up to a humidity switch for perfect control. Imo. This is the way to go to raise humidity in a larger room.

[Qwertywill]

Is you exhaust fan adjustable?

I think you are pumping out far too much air at any given point, That's why the RH% issue.

A 2x4x7 (Assuming height of 7') Tent should only have a CFM of 56 cu/ft + For air-cooled lights add 5%, for non air-cooled light add 10%-15%.

Assuming worst case you have 2x 150w hps lights that are not air-cooled add 17 CFM.

You should have a total of 73-75 CFM for your tent. (Try setting to 100 CFM in case heat issues)

Try this, and keep a close eye on the temp, if it gets too high adjust cfm slightly higher.... to allow cooler air in. (High temp = High Humidity)

What is your tent currently at for temp?

[Qwertywill]

Withdrawn.

[Toker1]

Weed Pharma is correct. Hot air has the ability to hold much more water than cooler air does. So if the volume of water in the air is held constant and you raise the temps... the ratio of RH % actually goes down.
In the example above, the moisture on the lawn comes and evaporates because of the difference in dew point temperatures.

https://sciencing.com/happens-relative-humidity-air-temperature-rises-22563.html

[Qwertywill]

"If you raise the temperature while keeping moisture content constant" .

Watering a plant is not keeping moisture constant. (As this goes up and down) It will never hit equilibrium.

Adding a humidifier would be a better chance to do so.

I do stand corrected Toker1 and @weed pharma
It will fall on higher temps.

I do feel however his airflow has a part to play with this matter based on the outside of the tent vs inside temps.

[Greenpassion]

All I can say is that these foggers are a godsend. They're so simple to set up, and they keep the humidity right where I want them to as they are on a humidistat, and the fans are waterproof. It is the most perfect setup for both my rooms. I initially tried humidifiers, even large room humidifiers that were evaporative and it did not do a thing. The Foggers have saved my grows!