Some Questions about my newest project.

[ThaRaven7]

OK, so I'm looking at working with a grow room that measures 8ft x 14ft or 112 ft. sq. Hypothetically, with 32-36 girls in it.

So, according to posts I've read, some people use a 50w per square foot ratio for HID lights, and some use a 62w per square foot ratio. By these two numbers that's 5600-6944w of HID lights. Does this sound reasonable? Accurate? Could I get away with less without greatly reducing yield?

Moving on to airflow and odor control. The plan is to buy a large air purifier, moving all exhaust through it on the way out. I've seen several types, including those that use activated carbon. I just want to be sure it's large enough. Please stop me if this is not a good idea. On the opposite side of the room would be fresh air intake. What numbers, in terms of CFMs should I be shooting for the exhaust and intake? Also, what size ducting? 12 in? Larger?

Any and all help is greatly appreciated.

ThaRaven7 Reviewed by ThaRaven7 on 09-27-2010. Some Questions about my newest project. OK, so I'm looking at working with a grow room that measures 8ft x 14ft or 112 ft. sq. Hypothetically, with 32-36 girls in it. So, according to posts I've read, some people use a 50w per square foot ratio for HID lights, and some use a 62w per square foot ratio. By these two numbers that's 5600-6944w of HID lights. Does this sound reasonable? Accurate? Could I get away with less without greatly reducing yield? Moving on to airflow and odor control. The plan is to buy a large air purifier, Rating: 5

[bigsby]

These calculations are easy but the depend on a number of variable. See the fan link in my signature.

[oldmac]

OK, so I'm looking at working with a grow room that measures 8ft x 14ft or 112 ft. sq. Hypothetically, with 32-36 girls in it.

Okie Dokie, I'll play along, Raven

So, according to posts I've read, some people use a 50w per square foot ratio for HID lights, and some use a 62w per square foot ratio. By these two numbers that's 5600-6944w of HID lights. Does this sound reasonable? Accurate? Could I get away with less without greatly reducing yield?

My rule of thumb is 1kw HPS covers abt 4'x4' or 16 sq ft. You have 112 sq ft so that would be 7kw of lights. Sooo... Yes, Yes & NO. But you do need to deduct an aisle space that you don't have to light unless you've mastered the art of human hovering.

Moving on to airflow and odor control. The plan is to buy a large air purifier, moving all exhaust through it on the way out. I've seen several types, including those that use activated carbon. I just want to be sure it's large enough. Please stop me if this is not a good idea. On the opposite side of the room would be fresh air intake. What numbers, in terms of CFMs should I be shooting for the exhaust and intake? Also, what size ducting? 12 in? Larger?

Well you did not give a ceiling hight so calculating volume of the room is difficult. Lets assume 8' high, that would give the room a volume of 896 cu ft. Looking at fans, a 12" should flow 971cfm but with a charcoal filter (which will weigh over 100 lbs) deduct 30% plus losses thru duct work another 20% or so. A 12" fan should be able to turn over room air every 2-3 minutes. That's pretty good. Air intake can be passive. You may want to check out an inline ozone air cleaner, much less restrictive then charcoal can and lighter too.

Any and all help is greatly appreciated.

No problem. One question for you, how you going to cool all those lights? And who's going to pay for it all?

[bigsby]

Air exchanged every 5 minutes is sufficient.

You are going to want to run two fans, one for the lights alone in a closed loop and one for the room to exchange the air and to deal with odor. Agree that an ozone solution is the way to go in this situation. Just be sure it vents external to the building.

Again, check my signature for a link to calculating your fan needs. It is best to account for the variables and do a proper workup.

[ThaRaven7]

Well you did not give a ceiling hight so calculating volume of the room is difficult. Lets assume 8' high, that would give the room a volume of 896 cu ft.

No problem. One question for you, how you going to cool all those lights? And who's going to pay for it all?

Yes, 8 ft high, sorry about that. Thanks for the reply! Very good info.

To answer your question... I'm not 100% sure yet. Each fixture will have a cool tube with a fan... and I've been toying with the idea of trying to converge them and exhaust them all through one duct. I think I can do it... but I'm not sure. So this means I would have two exhausts? One for circulation/odor control and another for cooling the lights/odor control?

As far as cooling, my partner and I have been discussing this. Because temps around here are going to drop soon, we're entertaining the idea of cooling the room with an active intake from outside. What do you think?

It's either that, or dedicate an AC unit to just the room. I'm open to suggestions.

[bigsby]

I suggest that you investigate hanging those lights vertically. You will gain significant efficiencies so you won't need as many lights, yields will be higher, fans will be smaller, and you have the space. If you go that route be sure to get cool tubes that allows removal of the reflector.

Yes, two exhausts. You likely can cool all of them with one duct if you use a 12" main duct (both in and out) with an appropriately sized fan. It pays to do ducting right. A small leak = big odor. Cooling the lights with an independent exhaust will greatly reduce your cooling requirements assuming you size the fan correctly. In fact, the secondary odor exhaust may provide sufficient temperature control (that may or may not be true in the summer). Again get the CFMs right. Add 15% to your final calculation and be sure to get fan speed controllers for both fans. Having the option of pulling fresh air from outside is never a bad thing except if the temps drop too much. You would need some way to control cold air intake likely via a duct damper.

[ThaRaven7]

Soooo, I've been looking at in-line ozone generators, and I think I found one I like.

Uvonair 12 Inch CD-In-Line Duct Ozonator

Now this may be overkill... but it fits a 12" duct, and it's not THAT expensive. Not to say $750 is cheap.

EDIT: With this big monster, could I go with something cheaper and less efficient for the other exhaust? Or do I need something as effecient?

[ThaRaven7]

I suggest that you investigate hanging those lights vertically. You will gain significant efficiencies so you won't need as many lights, yields will be higher, fans will be smaller, and you have the space. If you go that route be sure to get cool tubes that allows removal of the reflector.

Now when you say I won't need as many lights if I hang them vertically, if I positioned these lights absolutely perfect, how many could I get away with? Right now I'm looking at 6-7 1000w (I assume that's as high as I can go) HID's, but I don't know whether it's gonna be MH or HPS. With seven lights, the ducting is gonna be crazy.

[bigsby]

Soooo, I've been looking at in-line ozone generators, and I think I found one I like.

Uvonair 12 Inch CD-In-Line Duct Ozonator

Now this may be overkill... but it fits a 12" duct, and it's not THAT expensive. Not to say $750 is cheap.

EDIT: With this big monster, could I go with something cheaper and less efficient for the other exhaust? Or do I need something as effecient?

You only need to scrub the exhaust that is coming from the room. The lights you will duct as a closed loop. Air in from external source > through the lights > air out externally. No need to scrub this air as it never comes into contact with the room air.

[bigsby]

Now when you say I won't need as many lights if I hang them vertically, if I positioned these lights absolutely perfect, how many could I get away with? Right now I'm looking at 6-7 1000w (I assume that's as high as I can go) HID's, but I don't know whether it's gonna be MH or HPS. With seven lights, the ducting is gonna be crazy.

Run some searches. I can't answer your vertical light questions with any authority but there is plenty written about it. Use google to search these and other forums like this:

vertical HID "cool tube" or cooltube site:cannabis.com

Play with the search terms. Search other sites.

I'm going to say that hung vertically you could probably step down to 6 or 7 600w HIDs. The general rule is that you place the plants around the lights in a 2' radius so that's four feet / light. You will be growing bushes so figure 2' per plant as well.

Let us know what you learn!