How much air exchange?

G

Green007

New Member
I have a grow cabinet that is 26" deep x 44" wide x 74" tall.
It is in a small long room (144" deep x 44" wide x 74" tall) where temperatures average 55°-60°.
I will use CFL lighting so I hope that will raise the temps to 65°-80° (night/day), if not I'll stick a heater in there. (don't have the lights yet)
I do not have ANY vents in the cabinet, yet.

If heat is not an issue, how often should the cabinet air be exchanged?
How do you calculate that?

Then what is the easiest method to achieve it?
(be specific about vent and fan sizes if you can)

If heat did become an issue, would I then only need to increase the amount of air exchange?
 
Green007 said:
I have a grow cabinet that is 26" deep x 44" wide x 74" tall.
It is in a small long room (144" deep x 44" wide x 74" tall) where temperatures average 55°-60°.
I will use CFL lighting so I hope that will raise the temps to 65°-80° (night/day), if not I'll stick a heater in there. (don't have the lights yet)
I do not have ANY vents in the cabinet, yet.

If heat is not an issue, how often should the cabinet air be exchanged?
How do you calculate that?

Then what is the easiest method to achieve it?
(be specific about vent and fan sizes if you can)

If heat did become an issue, would I then only need to increase the amount of air exchange?
Click to expand...

Ventilation should be enough to maintain a temp of about 28C or 82F and a humidity of about 50% in the middle of the canopy but it's better to have too much than too little IMO. As a general rule I say about 120litres per second of air going in and same going out per square metre of floor area in summer. Thats about 3gal/second per square ft. You'll probably need a heater. Reptile ceramic heaters are best because they dont emit light and are pretty safe.
You'll need a fishtank heater for your nutes too if your doing hydro. Hope this info helps.:thumb::peace:
 
So I think I will need to run a heater both for air temp and for res temp in my Deep Water Culture. I'm gonna want to keep the heat in and only want to exchange the O2 for CO2 I am thinking. If heat is not an issue, do I need to vent?
 
Green007 said:
So I think I will need to run a heater both for air temp and for res temp in my Deep Water Culture. I'm gonna want to keep the heat in and only want to exchange the O2 for CO2 I am thinking. If heat is not an issue, do I need to vent?
Click to expand...

I'm not too sure but I think you need less fresh air if you use Co2. You still need to exchange the stale air. I always ask myself. Could I sit in there all day? If the answer is no then I don't expect my plants to. This method has always served me well through years of growing all sorts of plants. It's a bit hippy trippy but it works:hippy::thumb::peace:
 
You will need some form of ventilation in your room. Stale air won't help your plants. You need some sort vent, possibly a grate in the door, down low and a small exhaust fan up high. In addition you will need some sort of small oscellating fan aimed between the lights and the top of the plant to "exercise" the stems and make the stems bigger to hold more bud. If you can't drill holes then cracking the door open a couple of inches with a fan down low just inside the door to "pull freah air in and one up high blowing out the top of the door may do.
 
I thinke veryone offered you good advice.

There's going to be a big difference in Temps if you use like 6 42 watt bulbs or 4 105 watt bulbs..or some 200 watters can get much warmer.

And you have to consider in VEG, the lights will be heating it 24/7 and in Flowering, the lights will be off 12 horus a day, allowing the cabinet to cool.

I think I could advise you better if I knew what wattage bulbs you will be using. You need to determine which bulbs you will use, what size, and let us know, or set it up and see what the temps are. "What if" and "might be" is not as good as knowing and finding out. It might be that the bulbs get it to the correct temps in VEG.

You have a lot of varibles to deal with and consider. It will not be warm enough with LIGHTS OFF in Flowering, so some heat is going to be needed.
 
I plan on having 3 banks of lights and just turning them on as the plants grow. Start with 1 bank, then 2 then all 3. The light banks will be 12" x 24" with 10 -26W CFL's in each. I calculated that if the lights run the 26" direction in the cabinet and have them each take up 13" in width, the grow SqFt is 26" x 39" = 7.04sqft
7000L per sqft = 49291L
26W @ 1600L = 49291/1600 = 30.8 Bulbs


I do not want to have to use CO2 generator, so I want to accomplish that with air exchange.

MostlyCrazy - Based on the room size the cabinet is in, I think your right about having a low vent in the Door into the Room too.
 
The purpose of the air exchange is to get some natural CO2 into the grow area. Using "banks" of 26watts should not increase your heat too much but since hot air rises it will get hotter and hotter from the top down hence the need to vent it out up high. Something as simple as a vent booster should suffice. Think they are around $30-40 at HD or Lowe's. Can you vent it out on top? If not a cracked door and approriately placed fans can do the job with the small cfl's. You do lose the stealth that way though.
 
if heat isn't an issue, and you just want to exchange air and need to know what size fan you will need. I just estimate the size of the room in cubic feet so 2' x 4' x 6' is pretty close give or take a few inches so multiply those numbers and you get 48 cubic feet, you only need to exchange that air every minute or two, so a computer fan would work (they are usually between 30 and 60 CFM) as an exhaust. Intake can be passive.
 
Thankyou everyone for that input. I'll figure out where I can place the venting and still have it "steathy".

Maybe I'll modify and make it a free standing cabinet with vents out the top and bottom. But I hate to give up those precious inches.
 
Joe100 said:
if heat isn't an issue, and you just want to exchange air and need to know what size fan you will need. I just estimate the size of the room in cubic feet so 2' x 4' x 6' is pretty close give or take a few inches so multiply those numbers and you get 48 cubic feet, you only need to exchange that air every minute or two, so a computer fan would work (they are usually between 30 and 60 CFM) as an exhaust. Intake can be passive.
Click to expand...

Joe knows : )
 
Joe100 said:
if heat isn't an issue, and you just want to exchange air and need to know what size fan you will need. I just estimate the size of the room in cubic feet so 2' x 4' x 6' is pretty close give or take a few inches so multiply those numbers and you get 48 cubic feet, you only need to exchange that air every minute or two, so a computer fan would work (they are usually between 30 and 60 CFM) as an exhaust. Intake can be passive.
Click to expand...

+reps for you Joe!
 

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