Cool Tube vs Bare Bulb

Prawn Connery said:

^ We don't use hoods in vertical growing - that's why we don't need cool tubes.



I run 1200w in a 4'x4' closet and, as I said, I don't use cool tubes. Don't need to. And I grow in some pretty hot Aussie summers. Good ventilation is the key.

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For the sake of knowledge let me ask this...

Why are there such thing as cool tubes if bare bulb works so easily? Whats the main point behind it? What was the reason such a design was created?


Imo I would say watt for watt you could produce more with cool tubes in a 5x5 then normal reflectors.

Try and stick 3k's worth of hid lighting in a closet without a cool tube setup and you will see its a heat battle from hell. Cool tubes design is built on the principle to be all about heat control.

someone please correct me if im wrong but if I remember correctly u have to have a closed system to run co2 Effectively so your lose that option.

Again thats just my opinion Not arguing...


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Cool tubes serve one purpose: to duct heat directly away from the lamp. You can do that without a cool tube. Cool tubes were originally designed for horizontal growers battling heat under their hoods - that's why the first cool tubes had reflective material on one side.

You can try running CO2 in a closed system, but plants respirate during the lights-off period - when they need oxygen - so you'll find most CO2 growers only use gas during times of photosynthesis.

As for heat build-up in a closed system, all a cool tube does is duct heat away from the lamps and recirculate it - the hot air simply gets drawn back into the cool tube to be heated even further. That's why closed-system grows usually have aircons, dehumidifiers and other environmental controls.

Now, if you'd care to share the details of your 5'x5' 3000w grow, I'd love to see it! I'd also love to know how many watts per gram you are yielding.

Then we can compare it to my system

Prawn Connery said:

Cool tubes serve one purpose: to duct heat directly away from the lamp. You can do that without a cool tube. Cool tubes were originally designed for horizontal growers battling heat under their hoods - that's why the first cool tubes had reflective material on one side.

You can try running CO2 in a closed system, but plants respirate during the lights-off period - when they need oxygen - so you'll find most CO2 growers only use gas during times of photosynthesis.

As for heat build-up in a closed system, all a cool tube does is duct heat away from the lamps and recirculate it - the hot air simply gets drawn back into the cool tube to be heated even further. That's why closed-system grows usually have aircons, dehumidifiers and other environmental controls.

Now, if you'd care to share the details of your 5'x5' 3000w grow, I'd love to see it! I'd also love to know how many watts per gram you are yielding.

Then we can compare it to my system

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For the sake of knowledge I said...
Dont turn this into a pissing contest

What are u talking a cool tube recirculates hot air? Its intake is supposeb to be conntected to an area where it can draw in cold air...that would be pretty damn stupid to have a "recirculating" cool tube...

I use a air cooled hood now before I didnt but I probably dont need it considering 20-40F temps now

I have one vent hanging out the window sucking in that super cold air and a 240CFM fan pulling the air out of another vent and the air comes out super cold not warm in the slightest sense

banks dank said:

What are u talking a cool tube recirculates hot air? Its intake is supposeb to be conntected to an area where it can draw in cold air...that would be pretty damn stupid to have a "recirculating" cool tube...

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Then why did you mention closed systems?

banks dank said:

someone please correct me if im wrong but if I remember correctly u have to have a closed system to run co2 Effectively so your lose that option.

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You wanted someone to correct you if you were wrong, but now you don't like the answer

banks dank said:

Imo I would say watt for watt you could produce more with cool tubes in a 5x5 then normal reflectors.

Dont turn this into a pissing contest

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You claim "watt for watt" your system is better, but you don't want to compare it to someone else's system. Do you think anyone is going to believe your claims if you're not prepared to have them tested?

Same goes for your 5'x5' 3000w system: if you prove to us all how well it yields, then you might be in a position to tell us all what does and doesn't work.

In the mean time, I already know what does and doesn't work in my system - because I've been doing it a long time and have the results to prove it.

MedicatedGrow said:

I use a air cooled hood now before I didnt but I probably dont need it considering 20-40F temps now

I have one vent hanging out the window sucking in that super cold air and a 240CFM fan pulling the air out of another vent and the air comes out super cold not warm in the slightest sense

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A friend of mine runs a 3000w commercial grow and he runs air-cooled hoods, as he doesn't have the layout (or patience!) to grow vertically. I convinced him to take all the glass covers off his hoods and now he's yielding about 25oz per 600w bulb (about 125oz per grow).

His room temps are the same, his yields are higher (you'd be surprised how much light gets absorbed through a layer of not-so-clean glass) and all he has to worry about now is not letting his buds grow into the lights - a little extra tying down, that's all.

Now, some people may be forgetting this is the "Vertical Growing" forum, so I'll just remind everyone the question is: "Cool Tube vs Bare Bulb" - not "Cool Tube vs Horizontal Hood".

Prawn Connery said:

Then why did you mention closed systems?


You wanted someone to correct you if you were wrong, but now you don't like the answer


You claim "watt for watt" your system is better, but you don't want to compare it to someone else's system. Do you think anyone is going to believe your claims if you're not prepared to have them tested?

Same goes for your 5'x5' 3000w system: if you prove to us all how well it yields, then you might be in a position to tell us all what does and doesn't work.

In the mean time, I already know what does and doesn't work in my system - because I've been doing it a long time and have the results to prove it.

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Let me reiterated that the post are my opinion. Its my opinion.
And you get all hurt when someone is asking questions and u answer like your the final authority.

So cool tubes are completely useless in growing then?

Hmm thats weird...i wonder why they are sold since they have no benefit at all to bare bulb.


Since you know everything tell me why there is such thing as a cool tubes if they dont work any better than bare bulb? school me bro.

Side by side I still think u could run more watts than a bare bulb w a cool tube and honestly bro if I had the cash and time I would just to show you that I could.

Cool tubes can be utilized for a closed system. Im unsure why u think thats wrong. Sure u can have a closed system bare bulb but obviously heat will become an issue. That when cool tubes come in...
In Grow room design anything can be done...question is how practical is it.

Imo any light that was taken away due to a "dirty cool tube glass" would be compensated in the close distance that u could have the bulb growing to the plants...








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You're asking the same questions I and others have already answered. And it's not that I'm hurt (I really couldn't give a shit), it's that I don't really have a lot of patience for people like you who ask questions "for the sake of knowledge", then quickly dismiss the answers and insist you know better - even though you have nothing to back it up.

You're entitled to your opinion - and I'm hardly the final authority - but I'm not wasting my time answering the same shit over and over again for the sake of your ego.

banks dank said:

Cool tubes can be utilized for a closed system. Im unsure why u think thats wrong. Sure u can have a closed system bare bulb but obviously heat will become an issue. That when cool tubes come in...

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^ There you go again with your "closed system" - do you even know what a "closed system" is? Where do you think the heat goes in a closed system? Do you know anything about physics and heat conductivity? Do you even know the difference between horizontal and vertical growing and why we do it; why cool tubes don't have the same place in vertical growing as they do in horizontal growing? No, I didn't think so. Good luck with your grows.

there is a huge difference in cool tubes and open hood . in veg you will notice the mh bulb will kill your eyes in a open hood spreads very wide can do a shit load of plants off 1 bulb and in a cool tube its more direct to the plants. but does not look as bright. hps there also a difference. slight difference. I like to use flat hoods for bulbs work a lot better then cool tubes the flat glass ones not round. spreads the light more even to the plants. the cool tubes seams to be a few dead spots. I used to do nothing but cool tubes then I changed to cool hoods. with flat glass. . now who can handle all that heat from more the 1 open hoods ???? not me pump a 50 thousand btu ac unit @ 3 dollars an hour

In my experience during cool whether and with good fans air cooled bulb sealed room systems save big on the ac bill. Once it warms up a bit bare bulbs are much better and with the added benefit of a neater room with less cluster fuck..

kinddiesel said:

there is a huge difference in cool tubes and open hood . in veg you will notice the mh bulb will kill your eyes in a open hood spreads very wide can do a shit load of plants off 1 bulb and in a cool tube its more direct to the plants. but does not look as bright. hps there also a difference. slight difference. I like to use flat hoods for bulbs work a lot better then cool tubes the flat glass ones not round. spreads the light more even to the plants. the cool tubes seams to be a few dead spots. I used to do nothing but cool tubes then I changed to cool hoods. with flat glass. . now who can handle all that heat from more the 1 open hoods ???? not me pump a 50 thousand btu ac unit @ 3 dollars an hour

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Again, you're talking about horizontal hoods. Most vertical growers don't use hoods.

The theories applied to horizontal and vertical growing are different for one main reason: because heat rises. In a horizontal system, you generally have a hood (or cool tube) above your plants and the rising heat gets trapped under the hood unless you duct it away. Open hoods can also be ducted at each end, and do not need to be sealed to achieve this.

In a vertical system, heat simply rises and gets ducted away by the exhaust fan - it never gets trapped under a hood. Plus, you generally have a floor fan blowing directly on the bulbs which ducts heat away from them and cools them with a column of moving air - just like an air-cooled motorcycle engine uses wind ducting to conduct heat away.

It comes down to basic physics: you need to understand the physics before you can start to understand why some things work and others don't.

Same goes for "sealed rooms". There are two types of "sealed room" - one that is completely enclosed and recirculates the same air that is used for cooling the bulbs, and one that has the grow section sealed but draws cool air from outside through ducting and cool tubes, and then expels the hot air outside - the lighting system is not sealed inside the room, but runs a second ducting circuit. In such cases, yes, cool tubes do their job. But in an atmospheric system, as long as you have good ventilation and don't have heat-trapping hoods (which you won't in a vertical system), you really don't need cool tubes.

And as some vertical growers are already discovering, there is an optimal distance for plants to be away from the lights that is a trade-off between maximum PAR and light spread: giving max PAR to a few plants packed closely around a bulb may not give better yields than spreading the light over a larger area with slightly less PAR. It's all about finding the correct balance - and that usually comes with trial and error (otherwise known as "growing experience").

See the exhaust fan above this bulb? It is sucking heat directly off the bulb. The lower bulb is being directly fan-cooled. Do you see how close the buds are to this lamp? Do you see any burn marks or bleaching of the buds? This system works and has worked for almost 10 years, yielding well over 1g/w each and every grow.

Any tips on taking the glass off? It is glued on......i wanna go bare

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Is there not some way to remove the lamp plug and chord by undoing a few screws? That's how my cool tube is designed. It's hard to see from your pic.

That said, this is a great example of the amount of light lost through cool tubes. Just have a look at how clear the plants on the left are, where there is no glass, and then have a look at the plants behind the glass - see how dirty and opaque that glass tube is? This is exactly what I and others have been talking about. You can't argue with your eyes - have a look:

Fully nude!

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Thanks bud.

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Just ma 2 cents...I'm gonna agree with bare bulbing being the way to go unless space is tight.

nickelz419 said:

Fully nude!

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Way to go, dude! You won't regret it - just wait and see.