Humidity observation

Indoor Growing
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Ok, so I am obsessed with metrics at times. I have made sensors with ESP32 modules that measure and log temp, humidity, pressure (comes with the temp / humidity sensor), co2 and even soil moisture. There are a few cheapo hygrometer / thermometer combos that came with tents / lights that I have in various places as well, in addition to a dozen of those tiny hygrometers you put in your mason jars during a cure.

So, let me setup the scene. Current grow area is like 7x10, and beside it is another 10x18 room that has my cold water tank / well entrance, some storage with lots of shit, and a sump pit / sump pump (there’s one on each side of my basement due to high water table). Right next to the sump pit is a dehumidifier which drains directly to the pit to be pumped out regularly.

Dehumidifier keeps this room at almost 80F and about 55-58% RH. Running all the time right now. Basement is usually in the 60’s / 70’s and way high humidity (sweat in the floors, etc, adding the second sump pit has kept the basement dry for the past 10 years, whereas before it we had the potential to get up to 2" of water down there in a really wet storm). This room acts as a pseudo-lung room (no AC in it, but it dries the air before it gets to the grow room).

As such, I decided it would be a good place to hang my buds to dry as well. Its dark in there usually, temps are a little high for drying but not terribly so, and the humidity is just right. Its also the room where my 2x2 love shack is placed (right next to the dehumidifier). So, on top of the 2x2 I place a cheapo hygrometer, temp reads 77, RH is 58%. Perfect.

Well, I wanted to take some pics of a design I did for ebay, basically I made my own mason jar caps to replace the round metal disc, with a 3D printed disc that the cheap jar hygrometers can be mounted in so they are visible at the top of your jar without having to open the jar. I have a little place to take pics, so I snap some pics and leave 4 of these cheap hygrometers on a roughneck bin, the hygrometers are maybe 2ft off the floor. The hygrometer on top of the tent is 5ft off the floor, and I notice the lower ones are all reading 70-72%, while the one on top of the tent still reads 58%.

Well Shit I’m thinking, either the one on the tent is off, and I move that around alot and its been in the grow room for my quick visual for a while, or all the cheapo ones are off. I did put 12 of the cheapo ones side by side, and they varied by 2-3 % at most, so I figured the other one was off. Well, that prompted me to put the Jar tops on top of the tent to compare, and wouldn’t ya know it, they settle out at 56-58% RH as well…

So… My observation… And its been a few days, same observation every day now. At 2ft off the floor, my RH is 70%-72%. at 5ft off the floor it drops to 56% - 58%. I DO have a dual fan for a window (not in a window, no windows in that room) that I have in there to provide some air circulation, so its really interesting I have this seperation, almost like a thermocline of humidity, despite the air circulation.

Curious if the sump pit is constantly buffering from below, or the warmer air is just drier (there’s a couple degrees difference between 5ft and 2ft). The plants I chopped saturday are drying nicely, so I’m not so concerned, but its pretty crazy to me its almost a 20% difference in humidity just going up 3ft higher from the floor…

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That is a really interesting observation @nagel420 :thinking: is there a temp difference at those heights at all?

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Surprisingly, not much. 74F at 2ft, 77F at 5ft. its 82F at 8ft between the floor joists above. I feel the difference between 5 and 8ft easily with my hand, and its harder to notice between 2 and 5ft But the thermometer says about 3 degrees.

Another observation is maybe that fan is shit because I would expect it to blend the air more, but maybe not… I mean, it does blow like it should, kinda forceful and all…

Humid air is heavier? The top of the dehumidifier is about 28" tall, so thats in the high humidity zone, so to speak.

Its been really interesting to chart temp / humidity in the grow room as well, and see the correllation between them (lights off, RH rises slowly, lights on, it spikes down).

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I run fans at 2 different levels in my room a low and canapy height at cross ventilation. If that makes sense

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I don’t know how much moisture air can hold at those temps, or if a small variation in temp at that range can have that great of an effect that you’re having. I wouldn’t think so, but I really don’t know.

Lmaoo, that could be it. Maybe an oscillating fan would better circulate the air in that room, stabilizing the rh.

Thank you for posting this thread. Really got me thinking, which is pretty rare to be honest :laughing:

For the most part I’m a really smart guy, just trapped in a dumb guys head :joy:

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Great. Now you forced me to do an experiment tomorrow. Since I have plenty of the hygrometers I am gonna place em all over the grow room at various heights. I do have several fans in there, both above and below canopy level, all oscillating. Its only in the adjacent room that I am drying in that doesnt have an oscillating fan. (I might have to buy one, I think all I own are IN the grow room lol)

Its the only room without oscillation lol. Think I may have to run to wallyworld tomorrow for some cheap oscillating fans for that room.

As far as I know, and from what I see on my graphs, lower air temps hold more moisture, higher air temps lose it. As soon as lights go out, temp drops 5-6 degrees in the next hour, while humidity climbs at least 10% in that same time span. I’ll post a pic of my graphs tomorrow after lights on…

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Amateur psychrometry! Willis Carrier probably hashed out the math for this 100 years ago in Rational Psychrometric Formulae.

It’s always reassuring to see others with similar obsessions. I log data and record timelapses I don’t even bother to look at, but the data collection runs 24/7.

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My cheapo ones vary only 1%. It’s good piece of mind. Unless they’re all equally off and then you’re screwed :joy:

I also have two fans. One blasts below the canopy and the other blasts above canopy. They are very powerful fans.

Maybe a better mixing of the air would level it out for you🤷‍♂️

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As I think about it, in that room I probably should leave be. No plants, just cut ones drying. At 5ft the humidity IS good for drying at 55-58%. If I really get the air mixing, an avg of 77% and 57% is 67% which would be no bueno…

I am still gonna toss hygrometers all over that room and the grow room next door to it to get a visual. Curious if the layering is still present since the grow room has 5 oscillating fans, doubtful but we’ll see later on today!

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Hmm.

I’ve never used a sensor to check for layered humidity in the drying room. Maybe I should.

A good volume of fresh cut plants will throw off a lot of humidity. As they dry the humidity should drop a bit.

But it depends on a lot of things. Time of year, outdoor humidity, stage of drying.

If my convenient drying space were 70ish I’d probably be looking for a different space.

I’m lucky. I’m drying right now and it’s been raining all week and my humidity inside has been perfect at 60%. I don’t always get that lucky.

All the best.

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Aside from the attic, its probably my best option (and my attic is an oven, not really liking the idea). Main floor of the house no way, GF already complains of the skunky smell, and we aren’t big A/C users, with our windows always open and fans on, humidity on the main floor is easily 70’s or higher all the time

Air by me has been very humid most of the summer. Wet weather has kept humidity pretty high. Back in June when my tents were just getting started my in tent humidifiers were actually pumping out humidity because it was so low. I haven’t filled them since early July (in June I filled em every other day)

Volume of plants I would consider low for drying, its 2 smallish autos really. When I cut and trim the 8 other autos then its a volume to watch I think. But there’s literally a dozen branches of larfy bud drying right now… and its 58% RH at the height they are at :smiley:

I do know that the soil buffers a lot of moisture, and there’s probably 200 gallons of soil down there at least, all at floor level…

Not so worried about correcting / evening out the humidity in that room just yet, we’ll see after chop and trim of the inside autos though. For now its just an interesting observation, and something to learn about :smiley:

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Soil reads -3% because I took the probe out while watering and its still on top of the tent.

But look at the bar graph for temp and humidity.
Daytime temps avg 82-84, night is 75-76
Daytime RH is avg 59-60% and night it climbs to 67-68%

Really neat to see the graph and correlation. I could also see a rise in co2 when I was in the room (before I got the co2 bag), but now with the bag I see the co2 drops with lights off, and rises again with lights on… In all 4 graphs in the pic thats the prior 24 hours, so overlay them on each other in your mind to see the correlations. Neat stuff for sure, maybe a bit overkill for some, but I had fun assembling the system so far. Kinda like an erector set, but with cheap electronics :smiley:

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ps. I scattered all sorts of hygrometers at various levels in both rooms this morning. When I go down there later I am curious to see what each reads

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Slick looking dashboard. Did you whip up that design?

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Remember, this is relative humidity. As the temperature drops, it can hold less water and the relative humidity raises.

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Yup! Its basically Home Assistant, mostly stock stuff… Raspberry pi, some ESP32 modules with sensors, and TP link switches :slight_smile: Cameras are even ESP32 cams… Very affordable for the geek in me to assemble :smiley:

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This is awesome! Do you have anything running on ESP32 relays? What actions do you automate if any? I’ve been looking around for different grow automation systems but leaning towards Home Assistant since it seems more open-ended and much easier to use.

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In the grow room not yet, but I also have a model RR that I block sections of track using them. I do have some ideas for operating a 120v valve that I recycled from my washer though, and the relays will work with 120v, just haven’t jumped into that yet. I setup an 8 channel relay for shits and giggles, just looking for ways to integrate it… I probably could have made an outlet box and controlled it with relays instead of buying the switches, but I wanted the simplicity of the Kasa / TP link enabled switches really…

Temp and / or humidity trigger the exhaust fans, humidifiers and dehumidifier. You can see in my screenshot above that I have a target and tolerances for humidity and temp. Working on a few YT tutorials I got the basics together, then found a few other snippets of code I liked. The colored graphs are an add-on (free), because the stock was boring looking. The rest of what you see is vanilla home advisor, nothing special.

I’m not a coder, so I gotta find code / reverse engineer for my needs, but if you know basic coding, it’ll probably be very easy. Perl, C and Java / JSON would be super helpful, but its not an absolute, as I know NONE of them…

Seeing as I can measure soil moisture, my next integration will likely use that washing machine valve, triggered, and feeding a drip system. Since I’ll have to add nutes separately, it will have to be dialed in to provide the absolute minimum, and thats what I am researching now… I know the relay will trigger the valve perfectly… It would also work with 24v valves / associated power supply should I chose to ditch the 120v ashig machine valve and go with sprinkler / low voltage stuff…

Definitely a powerful setup, and so far to me only limited by my imagination…

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ok, so here’s the numbers…

Room adjacent to grow:
On floor 80%
2ft off floor 71%
5ft off floor 56%

Grow room
On floor 67%
2ft off floor 65%
5ft off floor 63%

Do note: the grow room has 5 oscillating fans, so its blending more. I only have the one dual fan in the drying room.

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Thanks for the detailed breakdown. I am also a decent code copy-paster so this sounds like it could work for me.

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If you have any questions along the way I’ll be happy to answer or point you to the solutions I used…

Really easy to integrate!

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