Humidity and venting help

[Fuzzy1981]

hi i have a yield labs 2'x4'x5' grow tent with a 400 watt m.h. light. 2 six inch ducting fans and a holmes wick humidifier. when the lights are not on i do not need to run my ducting fan for cooling purposes. but when the lights are on the heat gets to about 83 degrees or so, and i have read optimal temps are around 77 degrees. the problem is that for a seedling it says the humidity is best around 70 percent. when the lights are out and the ventilation is off the humidity stays where i want it but, as soon as i turn the vent fan back on the humidity drops to 30 percent which is the humidity of my basement (where i keep my tent) in the winter. i have tried wetting a towel and putting it in front of the fan, but it is not helping at all. with the lights on and no air circulation, the humidity stays at about 45 percent. i was wondering if any one had any ideas of what to do, is there a better humidifier? my thoughts are maybe an air wick filter is unable to quickly put humidity in the air to keep up with the dry air coming in. also i was thinking of ducting the light on both ends to blow the heat directly outside of the tent without introducing dry air into the tent. any thoughts or suggestions would be greatly appreciated. also i have vent fan controllers that let me adjust the fans to where they are just barely running and still it drops the humidity to 30 percent.

 

[Gadfly]

Low humidity isn’t a problem like high humidity. I wouldn’t worry about it one bit. Air flow is more important to me than dry air.

 

[Fuzzy1981]

thanks for the tip, this is my first time growing in a grow tent and im trying to dial everything in as best as possible. and to be honest it's kind of frustrating, trying to get things as optimal as possible. how much air do i need to be replacing the air in the tent? i feel like thats kind of a vague question, but im not sure how to word it better.

 

[Gadfly]

It depends who you ask. Everyone that wants to do it right goes through that anxiety to get it right I feel. Best advice I got, KISS. The books are nice, but they're not scripture. Just keep asking, and reading when you’re not sure. I learn something new every time I have a go.

You want to change all the air once or twice a minute. For example, I have a 3x3x6 space. So I have 54 cubic feet. Depending on lighting, heat temps, I could get away using a fan that operates between 100-200cfm. Keep in mind, that a filter, and every bend in ducting reduces the fans ability. I use a fan that operates at 200cfm. I say more air is almost always a good thing.

 

[dakotamoon]

I have (had - I hope exactly the same problem)! I have a 3 x 3 tent, and when the humidity was around 50% (summer) - my fan ran constantly - but it was pulling in moist air. Now that the RH in our house is 30%, major problems, with the fan on for more than 5 minutes, (keep in mind I have a humidifier in the tent) - it sucks the moist air into my attic, and brings in more dry air.. which is a problem. I tried jumping though hoops to find some way to slow the fan down, but with centrifugal motors.. that is a lost cause, when the voltage to the fan drops below 25% or so, the fan stalls .. so most solid state contollers don't turn it near slow enough. The "solution" is a climate controller. Who knew? I thought they cost a fortune, but they don't. I have a temperature controller coming from Amazon, $47 US. Now when my tent heats up past 75F .. the controller will turn the fan on momentarily - till the temp drops - and with my humidifier which is controllable - (will keep the tent moist as long as the fan isn't on constantly) this should get me through the winter. The same company Inkbird sells a humidity controller as well, if I need to I will order that next. I had exactly the same problem as you, very worried about my ladies, thank god for this forum. A great guy named Wally imparted that knowledge to me, and I gladly pass it on to you.

 

[dakotamoon]

As for how much air? That depends on your plants, mine are just at week 3 and need humidity and light more than a typhoon of oxygen at this point, it's my hope and opinion that once my 4 plants get older, they will start to create their own bio sphere with more humidity - then they will need the fan on for much longer when they "really" need oxygen. At this point it's only my 2nd grow - I haven't grown in this atmosphere before, (Canadian Winter xtremely dry) - so take my advice with that in mind.

 

[SamSmith]

I agree with Gadfly. High humidity and heat are way more of an issue than low humidity is. My tents usually run in 40% range. I have zero issues with it for seedlings, veg or flower. High humidity is hell on your electronics and death to a carbon filter. I run a 6" extraction fan with a carbon scrubber and a 4" inline CanFan pushing air into my 4X4 tent. Both are running full speed. I ran a humidifier my first couple of times and haven't since.

 

[dakotamoon]

Many here in this forum, and much of the research I've read calls for 70% humidity for the Veg state, and 40% for the Flowering stage. I'm just trying to give my plants what they need. I can only say that my ladies look so much healthier at 70% than they do at 40%! If you system works for You, awesome. RH requirements! The point is there is no set RH for all stages of growth.

 

[SamSmith]

This was taken in week 6. They were in the 40-50% range from seed. If you can get to 50-60% range without too much effort than by all means do it but if you can't I wouldn't lose sleep over it.

Tent-12-19-2018.jpg

• SamSmith
• Dec 20, 2018

 

[Fuzzy1981]

This was taken in week 6. They were in the 40-50% range from seed. If you can get to 50-60% range without too much effort than by all means do it but if you can't I wouldn't lose sleep over it.

Tent-12-19-2018.jpg

• SamSmith
• Dec 20, 2018

dang.. i hope mine look like that in six weeks. mine is three days old, and still on the first set of leaves, how long did yours take to get the second set of leaves? im just trying to get some idea if mine is growing at a normal pace or not.

 

[SamSmith]

When i said 6 weeks I meant in the flowering stage. Lol

This is one from that grow about 10 days old.

20180915_185746.jpg

• SamSmith
• Sep 15, 2018

 

[Fuzzy1981]

I have (had - I hope exactly the same problem)! I have a 3 x 3 tent, and when the humidity was around 50% (summer) - my fan ran constantly - but it was pulling in moist air. Now that the RH in our house is 30%, major problems, with the fan on for more than 5 minutes, (keep in mind I have a humidifier in the tent) - it sucks the moist air into my attic, and brings in more dry air.. which is a problem. I tried jumping though hoops to find some way to slow the fan down, but with centrifugal motors.. that is a lost cause, when the voltage to the fan drops below 25% or so, the fan stalls .. so most solid state contollers don't turn it near slow enough. The "solution" is a climate controller. Who knew? I thought they cost a fortune, but they don't. I have a temperature controller coming from Amazon, $47 US. Now when my tent heats up past 75F .. the controller will turn the fan on momentarily - till the temp drops - and with my humidifier which is controllable - (will keep the tent moist as long as the fan isn't on constantly) this should get me through the winter. The same company Inkbird sells a humidity controller as well, if I need to I will order that next. I had exactly the same problem as you, very worried about my ladies, thank god for this forum. A great guy named Wally imparted that knowledge to me, and I gladly pass it on to you.

that is a brilliant idea, when you bought your inkbird did it have two outlets for cooling, or just one? i have an inkbird for keeping the tent warm at night with two outlets but it's for heating only. i have noticed when the lights go out, and i turn of the fans for a bit the humidity goes right back up. so this idea seems like a winner to me. I live in the u.p. right under you guys and lake superior, it can get down to -35 to -40 at times (and for extended periods if we have a polar vortex go through) and with cold like that the furnace is running all the time. add in a wood furnace to the mix for heat and you have extremely dry air, and get a shock off of everything you touch. lot's of fun when you give your wife a kiss or pet the cat. the cat gets especially pissed if you accidentaly shock him. it's great to find a grower from up north to talk to, most of these forums deal with to much heat and humidity, the exact opposite of what were dealing with. when i was looking for a good way to heat my tent there was very little info that i found on that. i use a 500 watt heater hooked to an inkbird thermostat for when the lights go out. next thing im going to try and find, is ways to keep the heat in the tent with some form of insulation on the outside so it stays warmer longer and the heater will run less.

 

[Fuzzy1981]

When i said 6 weeks I meant in the flowering stage. Lol

This is one from that grow about 10 days old.

20180915_185746.jpg

• SamSmith
• Sep 15, 2018

i will have to take a picture and post it of mine in the next couple days. im not sure mine is going to be that big in a week. im growing northern lights.

 

[Fuzzy1981]

When i said 6 weeks I meant in the flowering stage. Lol

This is one from that grow about 10 days old.

20180915_185746.jpg

• SamSmith
• Sep 15, 2018

that is a really good looking plant what strain is that?

 

[SamSmith]

That is a Sour Diesel. This is her (a portion of her anyway) at that same 6 week mark. She is tucked in the back of the tent now so the first picture doesn't show much.

Sour Diesel 12-19-2018.jpg

• SamSmith
• Dec 20, 2018

 

[Fuzzy1981]

That is a Sour Diesel. This is her (a portion of her anyway) at that same 6 week mark. She is tucked in the back of the tent now so the first picture doesn't show much.

Sour Diesel 12-19-2018.jpg

• SamSmith
• Dec 20, 2018

That is a Sour Diesel. This is her (a portion of her anyway) at that same 6 week mark. She is tucked in the back of the tent now so the first picture doesn't show much.

Sour Diesel 12-19-2018.jpg

• SamSmith
• Dec 20, 2018

That is a Sour Diesel. This is her (a portion of her anyway) at that same 6 week mark. She is tucked in the back of the tent now so the first picture doesn't show much.

Sour Diesel 12-19-2018.jpg

• SamSmith
• Dec 20, 2018

those are really good looking plants! how long have you been growing for? i bought some sour diesel seeds but haven't tried to grow any yet. if my critical mass plant doesn't pop up in a few days, i may try germinating one of those.

 

[TorturedSoul]

2 six inch ducting fans

i was thinking of ducting the light on both ends to blow the heat directly outside of the tent without introducing dry air into the tent.

I'm a little confused by the above. You already have two exhaust fans, but you are NOT running a separate exhaust setup for your light? Then what on earth are you using the second fan for, lol, as a booster seat for your plant?

i have read optimal temps are around 77 degrees.

That's somewhat debatable. There's a relationship between the amount of light-energy, temperature, and CO₂ level. Basically, if your plant isn't receiving a great deal of light, then you'd want the temperature to be lower. But with a lot of light, the plant will be more efficient at a slightly higher temperature. (At lower temperatures, it won't be able to use/process as much light-energy.)

Speaking of light-energy, a short term solution for your problem(?) would be to use a smaller light until 400 watts are warranted - which, since you stated your plant was a three-day old seedling... does not currently appear to be the case. Turn off the metal halide and hang a 23-watt CFL an inch above the top of your seedling for now. Or, if you are using a dimmable ballast, turn it down to the 250-watt setting, that will cut your heat production by about 512 BTU/hour.

BtW, I wish I had your problem of low basement humidity. Half the time when I have to walk across my basement floor, I splash. Growing cannabis here is a little bit of a challenge - but growing mold is no challenge whatsoever. . . .

 

[HydroponicFireman]

The only time I've even considered humidity was growing in a high-humidity environment and that was with mold. I had to clean mid-crop and after harvest before starting again. I wouldn't even worry about low humidity. If you want to, just mist them once or twice a day with a hand sprayer or something. Indica strains are from environments that are high altitude and low humidity. I would personally say 70% humidity over a few months is way too much, I'd reserve that for seedlings only.

 

[dakotamoon]

There was some mention of high RH being bad for electronics. I received my inkbird temp controller today, the manual states: IT is designed to operate at up to 90% humidity. So I did some other research on electronics for the horticultural business. Like all grow tent lamps, fans, electronics are designed to operate in very high RH situations. ie a grow tent, or green house.

 

[dakotamoon]

that is a brilliant idea, when you bought your inkbird did it have two outlets for cooling, or just one? i have an inkbird for keeping the tent warm at night with two outlets but it's for heating only. i have noticed when the lights go out, and i turn of the fans for a bit the humidity goes right back up. so this idea seems like a winner to me. I live in the u.p. right under you guys and lake superior, it can get down to -35 to -40 at times (and for extended periods if we have a polar vortex go through) and with cold like that the furnace is running all the time. add in a wood furnace to the mix for heat and you have extremely dry air, and get a shock off of everything you touch. lot's of fun when you give your wife a kiss or pet the cat. the cat gets especially pissed if you accidentally shock him. it's great to find a grower from up north to talk to, most of these forums deal with to much heat and humidity, the exact opposite of what were dealing with. when i was looking for a good way to heat my tent there was very little info that i found on that. i use a 500 watt heater hooked to an inkbird thermostat for when the lights go out. next thing im going to try and find, is ways to keep the heat in the tent with some form of insulation on the outside so it stays warmer longer and the heater will run less.

Howdy, Sam just got my Inkbird today, it has one heating and one cooling 115v receptacle. If you are in the UP (beautiful country, been there many times) - then our situations are almost identical. Here is my CBDCritical at exactly 3 weeks. I don't know what your hydro rates are in Michigan, but here in Ontario they are insane. I did some research yesterday with kilowatt hours to see what my fan uses in one year of 24/7: $125 CDN and that's only 85 watts. So this Inkbird will pay for itself over a very short time.