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Hammo44

Ventilation advice

I'm planning a tent grow with a pretty small tent in an attic (tent size is restricted by space).

 

Setup for context: Tent size is 40cmX40cmX140cm and I'm running a rhino pro 100mm carbon filter connected to a 4" exhaust fan. Fan is connected to a temperature controlled fan controller.

 

I've got 2 air vents in the tent so my plan is to use passive air intake but I'm concerned about the air quality in the attic so was thinking of connecting ducting from the tent to a ceiling fan intake hole running out the bathroom below to pull in fresh air from within the house.

 

For reference, I'm venting extraction fan into the attic. I do have a roof vent which was connected to said bathroom fan but as its a first grow, I'm being cautious on venting outside and the smell - the attic space is pretty big so I'm hoping I should be fine venting into the same room as I'm venting a few feet away and 1.4m above the ground.

 

As I have a spare 4" fan, my question is:

 

1. Should I bother with active intake with the tent being quite small or just open the flaps and go passive? The air does get replaced - you can feel a breeze at floor level where the vents are but not sure if the plants will agree and reading up, fresh air from another room or outside is recommended.

 

2. If I go active, I'm not sure what speeds to set the fans at. Or is this something I'll figure out through temp and RH readings as I go along?  Both fans are the same model and both will be controlled but with a different controller. Cant find much online about setting fan speeds, just lots of info on calculating volume and cfm etc.

 

I'm only growing 1 maybe 2 plants but they won't be big because I can't fit big pots in the space I have. I'm using a mars hydro eco 300w LED.

 

Thanks in advance.

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Posted (edited)

It's going to pull in very wet air if someone's in the shower/bath, eh? Potential for the grey mush there (mold).

 

Decent carbon filter should leave no smell (never used rhino so can't comment) - but my mind circles back to the intake in the bathroom there, as really high humidity knackers the carbon's ability to mop up the stank.

 

You're aiming for a slight negative pressure...and, thinking it through, if it's two fans of the same type, but one has the extra burden of pulling through the carbon, you'll be at risk of pushing more air in than is being pulled out - although perhaps the longish intake may effect that. But, again, risk of stank. (eta - just read the two controllers thing. NM)

 

Sorry to be negative!

 

I found 'stepping down' my kit worked for me. In my case that was a 6" carbon filter, 5" fan and ducting, and a 4" fan doing intake, with a little passive so there's not too much suck. Ands a stepped controller thing. Worked well.Quiet, no smell. Perhaps a 5" out and 4" in, in your case? Passive, even.

 

 

Having said this, why not set up and have a play before planting up? Aim for the slight suck, and keep an eye on the humidity when someone in the shower? Get a feel for it,y'know. Post imagining stuff is not as effective as play.

 

eta? If the attic is undeveloped, you'll struggle with extreme swings, too. Insulate your box, mebbe, is that's the case?

Edited by j.o.i.n.t
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This is great, thanks. I never thought about the humidity coming out the bathroom. We don't have a shower in that room just a bath and it's not used often, maybe once or twice a week. I mean we do wash haha but we have an en-suite with a shower which we use instead. The window is open in the bathroom 24/7 hence why I thought it would be decent to pull in nice clean air. One thing to mention is the ducting length from the tent to fan hole is about 5ft because of socket locations and space. Do you think the length will negate the benefit of pulling in clean air? The ducting is pretty straight.

 

Until recently I only thought of using the vents for passive intake but got a deal on the fan which made sense to get 2 as I planned to run a 2nd tent for drying (I have a spare smaller tent but I was struggling for height with light distance so got a slightly taller tent) with just extraction and a 2nd carbon filter.

 

With the fans being the same size I'd planned to run the extraction at a higher rate than the intake to create the negative pressure by using the controllers. Hoping that would work and avoid floating the tent in the air.

 

I did build everything up and ran for an hour with one vent open and could see the tent walls sucking in so think I'm covered for negative pressure with passive only, it was mainly air quality that got me thinking of intake aswell. The other option I have is leaving the attic hatch open slightly to bring in fresh air. There's a window directly below the hatch.

 

I think with a first grow its easy to over think all the options!

 

I'm tempted to just go passive and see how I go with temps and RH. I've got the equipment available to go to active intake if needed.

 

Yeah the temp swings scare me a bit so I pushed the start date till late summer / early autumn but might need a heater for lights off. I'm doing autos so the 6 hours off will be during the day and lights on during the night.

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Posted (edited)

Yeah, I remember that over thinking...(long time ago now). Mine was an over worrying shit show. SK1, about an 1/8th, under a mercury bulb! I was hooked! :D

 

Weed is easy to grow, it's all this crap - the hiding it - that's most of the trouble. Dry runs (play!) really are worth it when setting up new space. Just let it tick over for a few days, see what happens. Tweak as needed. Rule of thumb - if you find it comfy they will too.

 

Keeping it simple, in many things, really is the best approach if it is also effective. I had both my in and out fans on the same controller, as it was the size difference that gave the difference in suck - but you'll be able to minic the same effect with two if you want to try, it's just more faffy. At these scales, though, as you suspect, and the led light, you'll probably be fine with passive - yeah. As for air quality, erm...I'd not worry about it (said from my limited position). Just get that used air out... which is why care should be taken with the making sure the carbon can do it's job. Even a couple of plants can stink.

 

I've never done an auto in my life. If you do a grow thread I'll follow along - I'm not growing at the moment, so do it vicariously.

 

Good luck mate :)

 

PS.

4" fans are pretty weak, if you get chance perhaps get a 5" and have it on low. Bigger stuff, turned down, is both quieter and gives the air more contact time with the carbon due to the slower air speed, but also shifting air due to the greater diameter.

 

 

Edited by j.o.i.n.t
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I would just stick with the passive intake, but make sure the extract ducting is pointing out the eaves, to prevent recirculating stale air

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4 hours ago, j.o.i.n.t said:

Yeah, I remember that over thinking...(long time ago now). Mine was an over worrying shit show. SK1, about an 1/8th, under a mercury bulb! I was hooked! :D

 

Weed is easy to grow, it's all this crap - the hiding it - that's most of the trouble. Dry runs (play!) really are worth it when setting up new space. Just let it tick over for a few days, see what happens. Tweak as needed. Rule of thumb - if you find it comfy they will too.

 

Keeping it simple, in many things, really is the best approach if it is also effective. I had both my in and out fans on the same controller, as it was the size difference that gave the difference in suck - but you'll be able to minic the same effect with two if you want to try, it's just more faffy. At these scales, though, as you suspect, and the led light, you'll probably be fine with passive - yeah. As for air quality, erm...I'd not worry about it (said from my limited position). Just get that used air out... which is why care should be taken with the making sure the carbon can do it's job. Even a couple of plants can stink.

 

I've never done an auto in my life. If you do a grow thread I'll follow along - I'm not growing at the moment, so do it vicariously.

 

Good luck mate :)

 

PS.

4" fans are pretty weak, if you get chance perhaps get a 5" and have it on low. Bigger stuff, turned down, is both quieter and gives the air more contact time with the carbon due to the slower air speed, but also shifting air due to the greater diameter.

 

 

Thanks for the insight. I'll try passive and see how I go. Interesting point on the fans aswell. I'm kinda committed with the stuff I've bought so far and the costs are racking up. Also, pretty right on space with it being 40x40. Had to pack it in tight. Managed to pick up a rubber coupler from a DIY place to connect the filter and the fan as ducting felt a bit flimsy even with rope ratchets. Took up what little space I had. Will maybe experiment if this goes well. Prices aren't much more for the bigger fans from what I see.

 

Need to convince the missus to let me use the spare room so I can get a bigger tent.

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Posted (edited)

14 hours ago, Hammo44 said:

One thing to mention is the ducting length from the tent to fan hole is about 5ft because of socket locations and space. Do you think the length will negate the benefit of pulling in clean air? The ducting is pretty straight.

 

Not sure if this is relevant now as you seem set on passive intake. I read all manor of calculations before buying my active intake (mine is 4" fan/duct) about this/that percentage loss for every twist/turn/additional length ducting. My intake connects to 10 meters of ducting (currently concertinaed - idea was could move active intake into another room - room tent situated always been warmest in house). As an experiment I stretched the full length of ducting out, made multiple 90 degree turns in it only to find almost no discernible difference in airflow at the other end)

 

large.Intake.jpg 

 

Another consideration is if decide to use passive intakes make sure the mesh over the intakes is up to the job. Silver box end of ducting is filtration box, this is a fairly clean back bedroom but after several months you'd be amazed at the dirt/crap it's trapped, couple small moths also.

 

12 hours ago, j.o.i.n.t said:

Weed is easy to grow, it's all this crap - the hiding it - that's most of the trouble. Dry runs (play!) really are worth it when setting up new space. Just let it tick over for a few days, see what happens. Tweak as needed. Rule of thumb - if you find it comfy they will too.

 

 

Never a truer statement was made, wasn't for hiding it all crammed into back bedroom, squeezing round tent to water plants avoiding the electrics, not daring to open window/curtains it'd be easy.

 

Best of luck with your grow anyway. Attic grow put me off due temperatures, freezing in winter, boiling hot in summer but equally it's not particularly well insulated. Pain in the ass going up there also. Spare room much better option if you can :) 

Edited by Poisonata
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15 hours ago, Poisonata said:

 

Not sure if this is relevant now as you seem set on passive intake. I read all manor of calculations before buying my active intake (mine is 4" fan/duct) about this/that percentage loss for every twist/turn/additional length ducting. My intake connects to 10 meters of ducting (currently concertinaed - idea was could move active intake into another room - room tent situated always been warmest in house). As an experiment I stretched the full length of ducting out, made multiple 90 degree turns in it only to find almost no discernible difference in airflow at the other end)

 

large.Intake.jpg 

 

Another consideration is if decide to use passive intakes make sure the mesh over the intakes is up to the job. Silver box end of ducting is filtration box, this is a fairly clean back bedroom but after several months you'd be amazed at the dirt/crap it's trapped, couple small moths also.

 

 

Never a truer statement was made, wasn't for hiding it all crammed into back bedroom, squeezing round tent to water plants avoiding the electrics, not daring to open window/curtains it'd be easy.

 

Best of luck with your grow anyway. Attic grow put me off due temperatures, freezing in winter, boiling hot in summer but equally it's not particularly well insulated. Pain in the ass going up there also. Spare room much better option if you can :) 

 

 

Nice insight on the ducting. Like you say, all I read was avoid creating bends and add 10% for this, add 20% for that. It's information overload to the max.

 

The mesh vents are pretty tight so hopefully I'm good on that front. Did see the bug filters which I might also use and defo if I go active intake.  I do like the idea of the filtration box aswell.

 

Agreed on the creeping about hiding it, just legalise it and tax it etc. Don't see that happening anytime soon with the clowns running the country now.

 

The attic is insulated so was more worried about the heat than the cold but hoping autumn is a bit more favourable with the extremes. Been getting plenty of practice going up and down the past few months not looking forward to lugging water and shit up there. Defo lost some weight with the crawling about sweating my nuts off!

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Posted (edited)

Hardest thing for me was convincing my wife the back bedroom was better option :rolleyes:. Ironic really, she smokes the stuff I don't, for me it was the financial saving and all the other annoyances like irregularity of supply, cost :eek: did I mention that already, general loathing for the people forced to deal with :furious:. Temperatures too high certainly the lesser of two evils, with good air flow they cope remarkably well.

 

Active intake definitely get a bug filter, even an old pair of women's tights stretched over the end are effective. Have you seen those new tights I've just bought..... :unsure:......lol Filtration box was £30 including delivery, filter is washable / re usable comes with all the clips etc never need a new one. First bug infestation and you'll rue the day you didn't bother 'nah, it'll be fine in the loft :naughty:'

 

Do a little pictorial diary of your set up / grow, holds readers interest & increases chances of responses in event you run into problems.  Each week I post pictures, looking at plants every day thinking, hmmm not grown much until you reference back to last weeks pictures :yep:

 

Good luck :) 

Edited by Poisonata

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Been busy the past few weeks so never got a chance to circle back on this.

 

Did a dry run over the past few days to measure temps and RH and checking the intake / outtake. Ran for 36 hours with no issues. Ended up buying a new 5" fan and same size filter, as recommend further up this chain. Wasn't keen on connecting the filter and fan with ducting so had a brainwave and bought a rubber coupler used for plumbing and tightened at either end to get a nice airtight seal. Also gave me a pretty sturdy connection. This worked well on the filter and fan I got with the grow kit but the new filter was too long. The kit filter was half the length. Didn't have the space so had to go with ducting and had to mount the fan outside. Seems to work fine and got good airflow out - was able to hang the ducting with only a slight bend.

 

Monitored temps and RH and temp range was 27-23 during lights on and 19-23 during lights out. RH went as low as 33 but sat around 35-50. The temp monitor says an all time high of 70 but not sure where it got that high as I was only checking every 2 hours. Waiting on delivery of a temp sensor that syncs with an app and let's you see historical values as a graph based on predetermined intervals. Can do it remotely so can check them when I'm not around. I'm thinking once there's plants in there and being watered, the RH should go up a bit. Got a temp controlled fan controller so hoping to control the temp better through that.

 

Definitely helped doing a dry run to see how the environment behaved.

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@Hammo44 You will have no worries once plants are in there, RH will rise as the pots and plants get bigger and temps drop a little too.

All the best, you're good to go. :yep:

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Thanks mate. Was thinking the RH would go up with the girls in there.

 

Itching to start now! 3 months of research and buying up equipment.

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