Is passive ventilation in tent enough?

Hey Guys
I'd like some info and input on how much fresh air plants need;
to grow up healthy, strong, and beautiful.
And whats the results cutting them short??

I'm using a large open basement that stays 59 degrees, @ 40-50% humidity consistently in the winter.
The 4'x4' x7' grow tent needs some heat, and I use a small bathroom style heater, controlled with a inkbird temperature contoller and some oscillating fans.
Humidity is raised during veg with a few strategically placed pans of water.

During early veg, I had no concerns on just leaving a few flaps open for fresh air ventilation.
But now that there coming of age, I wonder if that is enough.

For the past week I have been using my exhaust fan that I used last summer. I have it set to cycle for 10 minutes every 3 hours. Let the girls breathe a little. lol.

I should also mention, there is nothing wrong with my girls. They look good. Healthy from day one. Only thing I can botch about, is I wish they were bigger. Don't we all. hehe But there only a month old.

So what do you guys think.
The more I smoke, the more I think about this shit. hehe.

Will passive air only, be enough for veg through flower, or will it hinder growth?
Or... the big question... If more air intake is beneficial, is it enough to make up for the extra cost of your heater running more to maintain?
Ok, enough rambling.

Passive is all ive used for 2 runs so far in my 4x4x7 on my 3rd in there with zero problems.
I too use a cold basement or at least i did until i realized it was stunting growth big time.

What are your temps inside the tent.
Im guessing your running led lights?

Aby55 said:

Passive is all ive used for 2 runs so far in my 4x4x7 on my 3rd in there with zero problems.
I too use a cold basement or at least i did until i realized it was stunting growth big time.

What are your temps inside the tent.
Im guessing your running led lights?

Click to expand...

Hey Aby, Yea, I thought I mentioned it but I guess not. I use Vero29 COB lights and they fail to put off much heat. In fact I don't think they raise the temp any. That's why I use a small heater and maintain between 79 and 82 degrees. The small heater runs I'd say 80% of time to maintain. Also keep plants off the floor.
In the summer I can barely get by without supplemental heat.
Glad to hear passive ventilation working for you.

Highsince76 said:

Hey Aby, Yea, I thought I mentioned it but I guess not. I use Vero29 COB lights and they fail to put off much heat. In fact I don't think they raise the temp any. That's why I use a small heater and maintain between 79 and 82 degrees. The small heater runs I'd say 80% of time to maintain. Also keep plants off the floor.
In the summer I can barely get by without supplemental heat.
Glad to hear passive ventilation working for you.

Click to expand...

So how is it smarter to run leds plus heat vs a hps? A 4x4 likes a 1000 watt hps an will give a lb (in a 4x4) plus or minus depending how you grow it an what your growing. One of the big problems with leds is that they fail to keep the soil warm and thats something the led guys always fail to mention. I see a lot of noobies get suckered into expensive leds then run into problems.

If things are small an growing slow, maybe use those leds as supplimental an through a hps in there. I had a 600 true watt led panel i though was the shit in a 4x4 then i used a 1000 watt hps. An i shelved the led or used it as suplimental lighting. Leds just dont have the light penetration and power... a hps will also make the plant transpire more solving your humidity problems.

Well i have seen a lot of people using poly houses to grow marijuana as its helps in green house effect and keeping the atmosphere warm.
As this is winters in America and i generaly used to grow in tents or poly housed and with a certain amount of ventilation. ventilation is necessary as it helps in maintaing the proper temp and letting the oxygen come.

Growingforfun
You make some good points; but I would never claim it was "smarter" one way or the other. lol. Not enough proof or experience.
But I have thought about HPS or the likes, for killing 2 birds with one stone. But it's what I have now to work with.
Not sure where HPS would put my temps, but I bet it would be close.

Still fairly new to the game, you know. Nobody to coach or guide me when I started. Just going by info I mainly gathered here. Third run with this light, not overly impressed, but never used other types. I may change though.



Thanks for the advice.

I run a 1000w and in an 10x12x8 open room and had some heat issues with a wing reflector. You will absolutely want an enclosed hood, or a cool tube at the very least! With the intake air being the temps you described, about same as mine, I am able to keep room temps ~76.

Considering you can match the ppfd of a 1000w HPS with ~600 watts of high quality cobs, (which leaves you with ~400 watts to use for a heater) and you end up with light that eats up less headroom in your tent and doesn't require regular bulb replacement, I wouldn't exactly call it a case of 'noobs getting suckered'.... I've been growing since the early 90s and I love led lighting.

And the heater can be turned off during the summer. It can also be plugged into a nice digital temperature controller.

I know many people question and struggle with balancing ventilation and temperature or humidity.

Getting back to the ventilation question, how much is needed?

i like a good inlet that is passive, however i would always allow for the possibilty that the inlet would also need to be activated. I just think better to have all options.
so if i was buying the kit then i would buy every thing to do the job.

i did think many time about having a high output fan that only came on at the top temp in the grow area. at night, switch board has a outlet fan on trickle which is much smaller
so may ways to go when setting you stuff up.

last thing you want is super cold plants. they will not like you

growingforfun said:

So how is it smarter to run leds plus heat vs a hps? A 4x4 likes a 1000 watt hps an will give a lb (in a 4x4) plus or minus depending how you grow it an what your growing. One of the big problems with leds is that they fail to keep the soil warm and thats something the led guys always fail to mention. I see a lot of noobies get suckered into expensive leds then run into problems.

Click to expand...

yes you can run a 1000 watter in a 4x4 tent,but a 1000 watt light is better in a 5x5 tent,a 600 watt for a 4x4 tent.

NanoGadget said:

Considering you can match the ppfd of a 1000w HPS with ~600 watts of high quality cobs, (which leaves you with ~400 watts to use for a heater) and you end up with light that eats up less headroom in your tent and doesn't require regular bulb replacement, I wouldn't exactly call it a case of 'noobs getting suckered'.... I've been growing since the early 90s and I love led lighting.

Click to expand...

you can do but its rare.
most growers who try leds are usually disappointed compared to hps results.
yes there are very good led lights out there,but they are very expensive.
also you usually need to buy atleast 2 to cover the same area as 1 hps light.
yes some people build their own,but most cannot be bothered,or don't have the tools or know how.
imo a dual ended light is the better option,because a 630 de light can match a 1000 watt se light,plus you get great light coverage,penetration.

How many lights in that tent? 2 of the vero 3VL fixtures from timber grow lights heats up my 4x4 fast. I can run 4” fan/filter nonstop and still get a big temp increase

Highsince76 said:

Hey Aby, Yea, I thought I mentioned it but I guess not. I use Vero29 COB lights and they fail to put off much heat. In fact I don't think they raise the temp any. That's why I use a small heater and maintain between 79 and 82 degrees. The small heater runs I'd say 80% of time to maintain. Also keep plants off the floor.
In the summer I can barely get by without supplemental heat.
Glad to hear passive ventilation working for you.

Click to expand...

what kind of verys are you using? im running vero29 with a hlg 240- 2100mA, 3 cobs to one driver set up on a bar with remote ballast, 3 bars in total. 9 cobs, and they fucking get hot as shit to the touch, but i guess i am running them high.

I ran an air cooled 1000 in a 5x5x5 box
It works

But you just have to size your fan accordingly

Basments are great at maintainingtemps


I built a low hieght res and ran aero tubes so the system only took up about a little hieght

400 Watt Vero (4 COB's) with framework from Timber grow lights. 3000K. It uses two HLG-185H-C1400B dimmable drivers.

Running them at 300 watts at outlet.

I realize it's not near enough to supply a 4 by 4, but I'm only using approximately a 3 by 3 area of it.

Since I increased to wattage to 300 from 200, they are putting off some heat now; but not near enough to heat tent.

For ventilation I use a Soler & Palau 4" TD-100 In-line exhaust fan in upper vent tube hooked to a Electronix Express variac variable transformer.
It is presently turned down low as possible; just to keep fan running. I run it 24/7. A couple lower vent flaps are then left partially open.

And like I stated earlier, I have a small Honeywell bathroom style heater plugged into a Inkbird temperature controller set to 82 degrees.
It runs a lot; regardless if the exhaust fan is on or off.

Not the best or most efficient, but making it work.

Need to research more lighting before next run. I like what I've been reading on CMH.
Maybe a combination of LED and CMH.

Highsince76 said:

400 Watt Vero (4 COB's) with framework from Timber grow lights. 3000K. It uses two HLG-185H-C1400B dimmable drivers.

Running them at 300 watts at outlet.

I realize it's not near enough to supply a 4 by 4, but I'm only using approximately a 3 by 3 area of it.

Since I increased to wattage to 300 from 200, they are putting off some heat now; but not near enough to heat tent.

For ventilation I use a Soler & Palau 4" TD-100 In-line exhaust fan in upper vent tube hooked to a Electronix Express variac variable transformer.
It is presently turned down low as possible; just to keep fan running. I run it 24/7. A couple lower vent flaps are then left partially open.

And like I stated earlier, I have a small Honeywell bathroom style heater plugged into a Inkbird temperature controller set to 82 degrees.
It runs a lot; regardless if the exhaust fan is on or off.

Not the best or most efficient, but making it work.

Need to research more lighting before next run. I like what I've been reading on CMH.
Maybe a combination of LED and CMH.

Click to expand...

Highsin, I'm looking at that exact light set for a 3x3 tent. How hot does that set run?

This customer uses a 400W dimmable CMH light in his 4x4 tent, No AC needed, only a tower fan.
We have a Facebook group discussing grow lighting, welcome to join: https://www.facebook.com/groups/248519675519386/

Jeb, When running my Vero's @ 75% or 300 watts, I can lay my hand on a heat sink and keep it there no problem.
I still need to add heat to the tent to reach a good grow temp.

Sunplix, Them sure are some nice looking girls! You have my attention. I will be sure to check out that Facebook page. I am interested in expanding and running a CMH and that looks very interesting and guessing a high quality light.