So the weirdest thing happened. Earlier today the climate in my tent was great (~77 degrees and 65-70% humidity. They’re seedlings at this point.) now a few hours later the humidity has dropped to ~45% for no real reason. My humidifier is working I checked everything I could with that (changed the water, checked the filter, unplugged it plugged it back in, all the different speeds on it work so it’s not stuck in low I don’t think) I opened the tent a bit, I shut it back up, I turned my fan in the tent off, turned it back on. Cleaned the particulate filter on the intake fan too cuz that was actually clogged.
All of this has not improved my situation. The temperature is where it should be but it’s saying it’s very dry still. And it’s reading dry on the humidifiers gauge and the humidistat I have in my tent so I don’t think the humidistat is broken. I’m at a losS.
It oscillates so it blows air all around the tent. But it is pointed in the direction of the sensor. But the thing is it’s been fine for a couple weeks now and all of a sudden it’s all messed up.
lol yes I do see vapor coming out of the humidifier. It changes output when I raise or lower the speed just like it’s supposed to as well. I have it on full blast inside the tent with the plants and it’s still only going to 45% humidity
I even tried to turn that off to see if it changed. All that happened was it got colder in the tent which is weird to me. The humidity didn’t change. I just realized I had the intake fan on low so I turned it up to see if it changes anything.
Are you up north in winter and it got really really cold and outside RH dropped way down?
The rh in my house was 55-60 due to humidifier running into tent. Tent still at proper RH but house down to 45%
I just hooked up a second humidifier running into the tent the other day so my first one wouldn’t run all the time.
Outside affects inside
I am up in New England. Weirdly enough apple weather says it’s 65% humidity outside. It’s 18 degrees out too so 65% kind of seems not right. I do have a second humidifier. I’ll put that in there tomorrow to see what happens.
The plants look like they’re alright at this point. The leaves aren’t all turned up or shriveled like I’ve seen before when it gets really dry at an early stage. It’s late and I don’t feel like messing with them anymore tonight lol hopefully I wake up and they’re still alive and well
Could be the case….
It’s relative humidity and 18 degree temp can’t hold much water unlike 30 degree etc etc
I’m in Ohio and in basement and I’m glad I hooked up my second humidifier as I knew this would come as I’ve experienced in the past.
So the outside environment affects inside environment and once that 65% comes in via air exchanger the relative humidity in the house at 65 degrees drops way down so it happens
You can see how little moisture at max saturation air can hold at 14 degree F .14 versus at 68f it’s almost 10x moisture carrying capacity at 1.07
It’s all relative
When that super cold, dry air showed up, the importance of understanding vapor pressure (as measured in kPa) came to the front. Relative Humidity is is essentially meaningless for growers because it’s…Relative! It really doesn’t tell me what I need to know. kPa is the dance between temp and RH and is essentially the environment in which you are asking the plant to breathe and run all its processes. Think of it this way: your plant is porous. It takes in and expels water. Imagine putting one end of a towel in water. Eventually, the water will equalize; the whole towel will be wet. The amount of water in the tent is a absolute. The air at any particular time has a weight and a density. If the weight and density of the air around the plant is heavier (that’s low kPa), the plant will struggle to bring up nutrients from the roots. If there is less water vapor weight in the air than there is in the plant (high kPa), the plant will essentially pant. It is bringing up and losing water too quickly to efficiently photosynthesize. First instinct is to water them more. But water in the soil is only half of healthy hydration and it won’t get your plants going. The air around them really matters. Plants can survive within a temperature range. Same for RH. But it’s the combination of those two which produces proper kPa. Lots of great charts out there so you can see how they work together.
So to your question about what happened during that weather change, it was a big kPa swing in the ambient air outside your tent. If you’re running exhaust, the outside air is coming in. Your humidity probe may be correct but a single humidifier in a tent with an exhaust fan won’t keep up in that environment. What to do? If you can’t dial in a kPa around 1.0 by adjusting your fan, add a humidifier to the room. Get the ambient kPa to drop. Or you can adjust the room temp (which will adjust your tent temp). Slightly lower temp does not need quite as much water vapor to keep you in the range. Finally, you can vent your tent. In most cases, the air in the room is cooler and drier than that in the tent. I vent low if trying to raise kPa (less RH). I vent upper part of tent if trying to keep temp down a couple degrees. It’s always a challenge but if you take the time to wrap your head around vapor pressure and kPa, things get way easier.
