Which to Sacrifice: Airflow or Being 100% Light-Proof?

[GreenArmadillo]

Something that Nebula made me seriously consider these past few days.

My grow room looks something like the picture attached. My exhaust fan is in the very back. It's a built in part of the room.
Up until now i've been okay with slightly covering it using a towel to control whatever minimal light leak might come in from outside. The blue lines cutting across the exhaust fan in the picture represent this towel. I've set it up so that it's about 2 inches in front of the exhaust fan. This is so that the exhaust fan can keep working, and so that it isn't blocked. There is a 2 inch distance between the fan and the towel.

Now the reason this has worked up until now to prevent most light leaks is because our night here has been longer than the day. But now the day is slooowly getting longer, so this method isn't gonna cut it to completely block light leaks. I'm in the flowering stage, so doing 12/12, and I've synchronized the lights on and lights off of my grow room with the sun up and sun down up to this point. The day is now about 12 hours and 30 minutes long. So that minimal light when the sun is coming up, and when it's setting is still making some effects into the grow room. Now these minimal light leaks are enough for me to be able to see the outline of my hand when I hold it up in front of my face. So it doesn't count as 100% complete darkness for 12 hours. It's more like 11.5 hours of complete darkness, with 15 minutes minimal leak when the sun comes up and when the sun sets.

My flowering progress has been really slow up until now. It took 3 weeks of 12/12 for me to see the first signs of sex. I flipped the switch on the 3rd of February, so now i'm entering week 5 of flower, and there are still no clear bud formations. This is where Nebula suggested to me that light leaks might be slowing the flowering down. This made me stop and think.

So my question is...

1) Do I sacrifice airflow and completely cover the exhaust fan so as to ensure complete darkness until lights on?
2) Do I sacrifice being 100% lightproof so as to allow the air to be pulled out of the grow room constantly?

What are your thoughts on the matter, you lovely guys and gals?

[Weed Pharma]

Can you get a black mesh to cover both sides of the fan? This would prevent direct light leaks and allow airflow.
The internet wisdom is no light leaks or your world falls apart- that said: I use a nylon stocking over inlets and nothing on the outside vent.

I also, routinely keep at least one of the lower tent windows tented (open) to allow airflow- but also lets light in.
So far 12 grows with no issues and only 3 seeds in a year!
So while it's easy to blame light leaks/genetics etc..it hasn't panned out for me that way.
Keep a good environment that does not stress the plant for any length of time and all is well.

The plants will not adjust until after the first 2 hours of darkness - and there is dust/dawn etc.. in the wild.

In fact, they are developing a bio-stimulant which reduces the 2 hour time frame, so more hours of light per day could be used for greater yield.

[Flockshot]

You must have both, light tight and airflow. If you eliminate light tight your plant will not flower, or flower poorly. If you cut off air movement, you will risk mold and rot.

[9fingerleafs]

Without airflow you could run into some trouble. Having light In the dark circle can keep them from flowering so better focus on the light proof no doubt

[GreenArmadillo]

Wow, thank you guys for such speedy responses. I appreciate the energy. \(^._ ^)

Can you get a black mesh to cover both sides of the fan? This would prevent direct light leaks and allow airflow.
The internet wisdom is no light leaks or your world falls apart- that said: I use a nylon stocking over inlets and nothing on the outside vent.

I also, routinely keep at least one of the lower tent windows tented (open) to allow airflow- but also lets light in.
So far 12 grows with no issues and only 3 seeds in a year!
So while it's easy to blame light leaks/genetics etc..it hasn't panned out for me that way.
Keep a good environment that does not stress the plant for any length of time and all is well.

That sounds very promising bro. It's nice to hear that minimal light leaks don't necessarily cause problems for some growers. Let's pray that my girls are strong that way. =)
As for the fan, i've already taped all around it using gorilla tape and black bin bags, so no light leaks in from around the fan. It's literally only leaking through the part that the fan blades rotate.
As for covering the fan from outside, i'd love to, but there is no access to outside that window (it's not even a window, I can't open it). And i'm on the second floor, so can't get to it from outside either.

You must have both, light tight and airflow. If you eliminate light tight your plant will not flower, or flower poorly. If you cut off air movement, you will risk mold and rot.

I have two little dampness-absorbing boxes in my grow room for now, and they seem to be okay. I ordered a dehumdifier a few days ago, so should be arriving within a month. Hopefully i'll be able to control moisture to stop both mold or rot from even thinking of messing with my girls.
The one trick I have up my sleeve is that the room neighboring my grow room has a central AC opening built in from the roof. So throughout the day I open the door between the two rooms so that the temperature of the grow room can go down. Will that be any good to help air exchange as an alternative to the exhaust fan?
The main thing that worries me here is the possibility that the girls won't be getting enough fresh air and CO2.

Without airflow you could run into some trouble. Having light In the dark circle can keep them from flowering so better focus on the light proof no doubt

That's what I was thinking.
I thought I could perhaps uncover the exhaust fan and switch it on at 7AM before I leave for work, and cover it up and switch off when I get back from work, anytime between 4-6PM.
(My lights on/lights off schedule is currently 6AM/6PM)

But that would still leave the girls with no new air for 12 hours minimal every day. =/

[9fingerleafs]

If I were you I'd get some fans from the Home Depot. The ones with no light. Just a metal framed little fan. And let them run 24/7 inside your grow space. This will keep the moisture from gathering around the leaves and dispersing it to the air. Avoiding dew wich is the real threat.

about the light. Definetly try to get as light proof as you can. Even if it means covering/uncovering every day. Try what you said giving them as much time with air during the day. Get some cheap 1$ term/h meter and put them around your area and check how it behaves. This way you make sure what works and what's doesn't

[DW2]

GreenArmadillo, You need both. You do not want to restrict the air flow from Your fan by hanging something heavy enough to block the stray light. You could make an exhaust duct out of any thing like corrugated cardboard or foam board. Make it where it makes a gradual 90 deg. turn and spray paint the interior of it with flat black paint to reduce any reflected light. Here's a rough sketch to show what I mean. Make the duct slightly larger than the fan. Good luck on your grow.

[bobsakamoto]

i wonder if since your light leaks are concurrent only with the natural rising and setting of the sun if it even matters all that much....

seems to me that that particular kind of light leak would be just a tiny (question is is it insignificant?) variation of the way nature works...

that is, i wonder if not all light leaks are created equal if that makes sense? perhaps light leaks that occur constantly (even if small) or (big or little) light leaks smack in the middle of the 12 even if intermittent are the kinds of light leaks that cause herming.

just spitballin'

[yamiacaveman]

I always wondered how the full moon effects outdoor grows or is that reflective light different cause it sure is bright at times.

[GreenArmadillo]

It's like you say bro. From what i've read, most people share the opinion that because it's reflective light its frequencies are negligible to growing weed plants.
However, an interesting point someone once made was that lightning in some cases is enough to make some outdoor plants hermie.
Now ain't that nuts.

But as I said, these are opinions. Dunno how solid they are.

[GreenArmadillo]

If I were you I'd get some fans from the Home Depot. The ones with no light. Just a metal framed little fan. And let them run 24/7 inside your grow space. This will keep the moisture from gathering around the leaves and dispersing it to the air. Avoiding dew wich is the real threat.

about the light. Definetly try to get as light proof as you can. Even if it means covering/uncovering every day. Try what you said giving them as much time with air during the day. Get some cheap 1$ term/h meter and put them around your area and check how it behaves. This way you make sure what works and what's doesn't

I already have one 12" oscillating fan in the grow room. It's on most of the time, but i've attached it to a timer so as to switch off for a few hours every 2 days or so.
You suggested keeping the fans on 24/7. Is that safe, electricity-wise? Will the fans be able to take it? Anything to consider if i'ma leave em on constantly?
I was actually considering buying a 16" fan next week and adding it to the grow room. My current fan only blows mid level on my girls.

GreenArmadillo, You need both. You do not want to restrict the air flow from Your fan by hanging something heavy enough to block the stray light. You could make an exhaust duct out of any thing like corrugated cardboard or foam board. Make it where it makes a gradual 90 deg. turn and spray paint the interior of it with flat black paint to reduce any reflected light. Here's a rough sketch to show what I mean. Make the duct slightly larger than the fan. Good luck on your grow.

That's a super idea man. I'll definitely look into it. For the long term, this seems like a much better solution than covering the exhaust fan.

i wonder if since your light leaks are concurrent only with the natural rising and setting of the sun if it even matters all that much....

seems to me that that particular kind of light leak would be just a tiny (question is is it insignificant?) variation of the way nature works...

that is, i wonder if not all light leaks are created equal if that makes sense? perhaps light leaks that occur constantly (even if small) or (big or little) light leaks smack in the middle of the 12 even if intermittent are the kinds of light leaks that cause herming.

just spitballin'

tbh bro, I was thinking in similar terms to you. It makes sense. But honestly, I don't wanna risk it with my girls. They've been really slow to even start budding, so maybe this minimal light leak might have something to do with it. Or it could just be the strain. After all, i'm growing an unknown strain. Most likely something that grew in India, and was imported to my country as super dry buds.

[9fingerleafs]

It depends on your climate and how your grow room is behaving. Without some RH / temp meters you will never actually know if you need more airflow or humidity or too much heat etc. I let the little fans runing 24/7 with no problem. Just depending on how "dusty" it gets but usually need a cleaning once a week. The problem with humidity is the leaves expire it so a thin layer of moist air is surrounding them all the time. So anything that disperses this layer is good unless you have low humidity. About the heat. Leaves can take humongous amounts of heat and energy but the roots don't. So even when just below the lights in the canopy is 30 C down in the roots is 26 C so no problem there. Where I'm going with this is no one can help you rigure out how to improve your grow room but you. Cause every situation is unique. Get some 1 dollar meters and learn how your growspace behaves

[GreenArmadillo]

Will do man. Already have ordered a few cheap hygrometers. I'll defo do what you suggest. atm there's only one digital hygrometer in the room, and i'm monitoring it daily. My temps range between 20o and 29o. My humidity is between 35% and 52%. (I have two dampness-absorbing boxes in the grow room until my dehumidifier arrives, and they seem to be helping out)

Love the advice bro. ^_^

[9fingerleafs]

Those are perfect conditions to grow. Most people spend lots of money to recreate those conditions. So as long as you give your plants their 12 hr darkness you gonna have great buds

[GreenArmadillo]

Can you get a black mesh to cover both sides of the fan? This would prevent direct light leaks and allow airflow.

BRUV!! Man, funnily enough I was walking around a random shop yesterday. I turn a corner, and guess what I see STARING AT ME in the face.



So today just before blackout, I done just as you said and installed over my exhaust fan. I used a double layer. I think I can still feel some form of airflow. Does that make sense?
I'm hoping that the air can still make it in and out.


So my exhaust fan used to be set up like this (Notice how the towels are laid out in front of it):

<---


And now, after adding the mesh:

---> ---> The Result --->


Man, I know it's kinda messy, but Gaaaaaadaaaaamn I fuckin LOVE growing. This DIY $hit is so much fun. Haha, the feels you get when you overcome a problem you've been faced with.
Hopefully that's me neither sacrificing light-proofness nor airflow. Hope the girls love it.
I'ma check the morning sun-up just before lights on to make sure this does the job.

Thanks for the advice everyone.
If you have anything to add please do. I'm all ears.

[bobsakamoto]

This DIY $hit is so much fun. Haha, the feels you get when you overcome a problem you've been faced with.

so *SO* feel you on this.... and if your attitude and diligence is any indication i think your girls are gonna turn out fantastic!

oh, and just to tie up a loose end, i didn't mean to be suggesting that you "wing it"/guinea pig your girls on this particular grow w/my comments about "natural" vs "unnatural" light leaks....like i said, i was just spitballin'/offerin' food for thought.

but like yamiacaveman i have seen some insanely bright moonlight--esp the further away you get from humans/ambient light-- and wondered about it w/respect to growing...... makes sense of what you said about plants herming in nature.

oh, and in case this might help you (or anyone else) in the future...i learned from one of Nebula's tutorials that moonlight is one lux--now whether that's ALL moonlight i don't know (see above.)

[GreenArmadillo]

haha, fuck yeah! Makes me happy to see that we all feel this way about growing.

And not at all bruv, don't worry. It's all love baby.
tbh, I think these particular girls would have been okay with the minimal light leaks we were talking about. I've gotten the idea that they are quite resilient.
But after switching to complete darkness, I can totally see clear bud development now. Dunno if it's a coincidence or not, but don't really care.
I'm just so stoked to see buds growing. It's magical! <3