Tent airflow

[flylowgethigh]

I have my tent and lung room working great as far as humidity and temperature are concerned. Plants are vigorous and seem happy, but I want them making tric heads. The CO2 meter reads 575 at daybreak when the light comes on, and gets higher up in the 700 range during the day as the dawg and I migrate toward that part of the house. There are plenty of clip-on fans moving the sit internally.

So my question is, what about the airflow through the tent? Can I use the CO2 reading in any way to determine if the flow is adequate? Does more airflow help build the flowers?

 

[Ca++]

That's a nice co2 level for free.
I don't think the level is an indication of airflow adequacy or deficiency. Though if your circulation is poor, then you might be able to improve on that, and thus reduce the level through the plants usage of it. Just the data you have isn't saying much though

 

[dogzter]

Cubic sqf of tent and cfm need to match somewhat and intake should be low on one side and outflow should be high on the other so the air is forced through the plants.

 

[flylowgethigh]

I have one fan pumping in filtered air to the floor, two fans sucking air out the top, two fans at the top of the soil pot blowing the floor air vertically up, three fans blowing down at angles from the corners at the tops.

The lung room has a space heater that keeps the tent VPD and temp at 78*F, 40% at the tops, a little cooler at the soil level.

Top area runs 73-74* at night. If I shut off the space heater at night, I can get the temps down to 65*. I am wondering if that is a good idea . Starting the 5th week of flower soon… 8 week strains. Does the night time make frost, or daytime?

 

[Ca++]

Bruce Bugbee is onboard with lowering temperatures throughout bloom. His goals may be chemical products, not plant weight though. Obviously terps will not leave so fast, but many of the products are stress related. I have seen no studies regarding this, but there are other aspects like colouration, and the electric bill. The important precursors though.. I dunno

Your fan arrangement doesn't sound lacking. It's a bit cold and dry though. I would perhaps start with insulating the tent. Even a simple sheet adds an air layer you don't have at all. A single duvet on the roof, dangling down the sides a bit, can be worth a lot. Tents alone offer next to no insulation, and instead are usually black body radiators, with increased surface area due to texture. It's not what many of us want. Your extract speed might also be excessive. You speak of two extract fans. As an example, my fan is turned down a fair bit, and it's a 4" set. In places more, in places it's less. This is doing a couple of meters. I would go lower, if I didn't have negative pressure concerns. I have negligible co2 drop through the tent, because plants take hours rather than minutes to make an impact.

 

[flylowgethigh]

I used to have 2 each 4x4 tents next to each other, with a 8” manifold of two 6” entrances in the tent nearest to wall opening, which also has an 8” fan. The other tent fed its 6” exhaust into the 6x6 x8 wye as did the tent with the manifold. When I took down the second tent I kept both 6” fans in the remaining tent, and run them slower.

I couldn’t care less about weight, but firm frosty stick terpy nugs would be nice.

 

[Mate Dave]

I think unless you are running a sealed environment, as best as can be that isn't hermetically sealed there will always be a depletion of Co2 greater than the plant will use otherwise.

Temperature humidity and all things effect airflow..

The space with the plants and any other connected areas must pressurise and build in concentration, at this time it's wise to use only circulation.. I would have the PPM's start rising 15 mins before lights come on. You can saturate them at this stage because your AC and or ventilation will kick in once a limit is hit and then you will have to keep up with any environmental controls and it will reduce the Saturation PPM.

The rooms 'Sitting temperature' is the Limiting Factor to consider here. It's diel fluctuations at on and off effect how you maintain optimal gaseous exchange.

This can be maintained for long periods with cleaver lighting control.

Ideally PPM of Co2 varies so the peer reviewed journal and articles I've studied show. There are key factors that lights play that mean various things for ideal level.. Anything is better then nothing tho right..

Measuring the optimal periods for gassing and when to ventilate seems like headache.. I'll look for a paper or 2 on it from studies I'm sure there's a bell curve to hit for outdoor assisted protected grows as per peak UV and when it's best supplemented. All day or at periods or high exposure..

As long as you're getting enough air exchange you don't need much Co2.

 

[flylowgethigh]

My meter averages 600. I was just wondering if letting the temps drop at night and come back up during lights on was a good idea. Going from around 73* lung room to around 65*.

 

[Mate Dave]

Look at the bell. Is it worth any more expense to flatten the curve? This is for C3 plants specifically, and not specifically cannabis but studies based on bedding plants, nursery stock and edible crops. PPM of 800-1000 all the way to saturation has shown responses in various genus from 40-100% increase in biomass.

I would keep a fluctuation in diel temperatures, it's natural isn't it letting it creep up to optimal by lights on, if you have supplemented the PPM and can heat the chamber try it.. I would up the PPM during the day more than temp considerations.. Your question about do they frost at night or day. They are C3 plants and store energy during lights on and release Co2 even take in oxygen etc for a period at lights out so no need to supplement it or keep stable ambient temps keep the PPM at a level you can reach saturation before lights on and keep it above 800+ all lights on. Stomata open when the chloroplast senses blue wavelengths.

I'm looking for a Phd study or similar on the new term 'Crop Steered' or 'Dialled', a cannabis specific study for increase in biomass and cannabinoid content with references to Co2. I have a study done at GW Pharmacuticles on my hard drive.

Ambient PPM from 800-1000 is the 'Goal' with supplementation and with the Co2 benefitting LED supplementation rather than excessive temperature humidity spikes that vaporise the good stuff.

I like to grow between 19c cold and 23c to get the aromas and the good stuff I want.

I've ran at hot and low temps and even had rooms/ attics etc at night that are in excess of 31c and been in the 40's during summer conditions, basements that flood and freeze almost, it ain't nice. Plants in Veg don't mind fluctuations so much, it's the latter stages of flower that really counts to have the environmentals sorted. Obviously any nastic motions from extreme fluctuations in environmental controls of temperature those which reduce metabolic rates and cause oedema or other pressure loss in plants will stunt growth but a good 3 week run in before differentiation and a good 6 weeks of good ambient during the building phase unto week 10 up to when they start to mature and stress into unpollinated flowers, as this is happening it's wise to reduce humidity and heat whilst you are waiting for them to 'frost out' ripening any resin.

 

[chronosync]

Edit *** see below

For any given space you want air exchange 1 - 3 times per minute. 3 times is optimal.

2x4x5ft tent = 40 cu

120cfm fan is needed

 

[flylowgethigh]

My CO2 level is unsupplemented, unless the dawg being in the room with me counts. As for air exchange in the tent, I think changing the air every 20-30 seconds would be noisy. No idea what the flow rate through the tent is, but the humidity up at the tops is only a couple points higher than the lung room.

I’m just thinking about the Mendocino mountains getting cooler at night.

 

[chronosync]

For me it’s a 4” fan with filter turned about 75 percent to full blast. It doesn’t even cave the tent.

 

[chronosync]

I must digress. 2 x per minute is max recommended and 0.2 is the minimum plant requirement (according to ventilation 101 thread)

I had 3 x per minute recorded in my mind as fact but I was mistaken. Dun hav’n even says 2 x being max.

My apologies but thanks for giving me the opportunity to relearn what I thought I knew.

 

[Ca++]

I'm not sure where those numbers come from, or who ever measures. I have an airflow meter and duct adapter, but still it's importance seems low. So I have not used it. I have looked at co2 use, in terms of inlet and exhaust, and all I can say is, I'm not sure where those numbers come from.

 

[Mate Dave]

"Overkill is underrated"
I get what you're saying about the structural reliability of tents and air movement. You can buy add on attachments such as the 'Space saver' to prevent an implosion these days.



The plant in the pic early 2000's was using 1x 8" exhaust fan and 2x 4" inlet fans. The SCROG frame helped with the rigidity of those old 1st Generation tents. Later models have much more integrated selection choices, a range of ventilation choices, pole sizes, crop bars/ support and refractive properties.

If you need more holes cut some..