Need advice on grow room

I pretty much know what I need to do to help with my high temps and low humidity, but I just can't figure out why I'm having these problems when I never had them before in the past.

Back story....I was using a 6x6x6 tent with two 600w mh/hps lights, one small table top fan (diameter was about 5 inches across), a 450cfm inline fan with carbon filter attached, and just one vent hole open about 2 ft away from the fan to bring in some fresher cooler air from the room. The highest the temps would get during the day would be around 88, but it wasn't all the time. The lows at night would drop down to lower 60's. Humidity....in the morning before I opened the tent doors it would be basically 100%, well maybe more like 90 to 95. It was so humid that the ceiling in the tent would drip water, the walls would have water rolling down it on the inside. If felt like a sauna. Running a homemade NFT system, so that probably helped raise the humidity levels from all the evaporation going on from the res. Once the doors were opened for about 30 minutes the humidity would drop down to the normal 40 to 50%. I had to keep the doors open cause it would build humidity back up real fast.

Now, I built two separate rooms. One is a smaller 3x7x7 for vegging and cloning, and the other one is 7x8x7. Running two 600w hps lights, same inline fan and filter, upgraded to two fans, one is a bigger table top fan with a 12in diameter and the other is a stand fan with a 20in diameter, both set on high. NFT system still running, so no difference in the system. I have two vents in the small veg room that measure 10x5 and 10x8. The flower room has two vents the same size as well set on the opposite side of the inline fan and filter. Daytime temps average 92, humidity around 20%, night time temps drop down to the lowest of 85 and humidity stays the same.

Any ideas on how to lower the temps without using an a/c unit. I already have a cool mist humidifier, which I'm a little afraid to use cause it sprays a mist out and I don't want it blowing my lights if the water droplets happen to make their way that high.

Thoughts?

You need to run your exhaust 24/7 in your flower room and however long your lights stay on in veg.
Unfortunately upgrading to a bigger space also means upgrading your cooling power. More space = more heat buildup. Running your exhaust constantly while lights are on will help, but only to an extent.
Also, you may need a dehumidifier for your bloom room, as NFT puts a lot of moisture into the air, which you do not want in late flower.

JayJammer said:

You need to run your exhaust 24/7 in your flower room and however long your lights stay on in veg.
Unfortunately upgrading to a bigger space also means upgrading your cooling power. More space = more heat buildup. Running your exhaust constantly while lights are on will help, but only to an extent.
Also, you may need a dehumidifier for your bloom room, as NFT puts a lot of moisture into the air, which you do not want in late flower.

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Even in AK, where our outdoor highs have been 70 at the highest and just for a few days at that, I could not cool my room by just exhausting air. If possible it helps to draw cold air in from dank crawl spaces. Not attic crawl spaces but basements or crawl spaces. If I can use a 6" line to draw feed air into an airtight woodburner and heat most of a house, one can do likewise cooling a room or helping cool it. Not the solution but part of one. I open a window here and place a box fan in it. A luxury most don't have I'm sure.

Thanks Jay and Hotrod. I wouldn't have thought that a bigger space would build more heat, I figured it would be cooler. Just like when you are trying to heat a room if you have tall ceilings, it takes more energy/heat to get the temps up. I have a vent that's around 10x5 one the back side of the room at the bottom. On the other side of that wall I built is the far end/corner of the basement where it stays cool, around 68. I sat the table top fan in front of that vent in hopes that it would pull the cool air into the room. On the opposite side of the room I have another vent but at the top of the wall so hot air, (which rises) could flow out, it's the same sized vent. I also have the inline fan running 24/7, I disconnected the duct that goes from the furnace to the attic and attached the inline fan duct to that so it blows all that air into the attic. I went down earlier today, temps outside are currently 70, but the temps in the bloom room are sitting at 92 already and the humidity is 45%.

Yea, those NFT systems do put out alot of humidity, that's one reason I like them when vegging, but I switched back to a homemade aero tote to veg/clone in. Trying a perpetual grow this time. Eventually I'm going to get a small window a/c unit and cut a hole in the wall and put it in there to help cool the room. I'll set up some kind of apparatus to catch the dripping water from the a/c unit, even though the basement floors are concrete so it wouldn't hurt to drip. I was just confused that a larger room would stay hotter than a smaller one when using the same lights, inline fan, and added two fans. I guess in the mean time I'll play around with the setup to see if there are any changes.

Do you think I should upgrade to a larger inline fan? Right now I'm running a 450cfm 6in inline fan to pull through the carbon filter. Maybe a larger one would help pull more hot air out of the room. I remember reading somewhere on here that you should have a negative effect(?) or something like that when it comes to ventilation. How can you tell if you have that?

yeah you need something larger to exhuast both those rooms personall i would buy another fan/filter combo just for the veg room and dedicate the one you have for the flower room (or vice versa should you buy the same size fan and filter)

only other option as far to keep it all one filer is to use an 8" or 10" fan, not the same filter you have because if you upgrade the fan your gonna need to upgrade the filter.

JayJammer said:

You need to run your exhaust 24/7 in your flower room and however long your lights stay on in veg.
Unfortunately upgrading to a bigger space also means upgrading your cooling power. More space = more heat buildup. Running your exhaust constantly while lights are on will help, but only to an extent.
Also, you may need a dehumidifier for your bloom room, as NFT puts a lot of moisture into the air, which you do not want in late flower.

Click to expand...

More space equals more heat only if you do not exhaust the stale air being generated by your grow. Ever notice that in a small confined space takes less time to heat up than would a significantly larger area.

polyarcturus said:

yeah you need something larger to exhuast both those rooms personall i would buy another fan/filter combo just for the veg room and dedicate the one you have for the flower room (or vice versa should you buy the same size fan and filter)

only other option as far to keep it all one filer is to use an 8" or 10" fan, not the same filter you have because if you upgrade the fan your gonna need to upgrade the filter.

Click to expand...

Yea, I was thinking of upgrading the fan/filter combo to an 8 or 10 but not sure yet. I think it would be cheaper to buy a 5000btu or a 6000btu window a/c unit to install down there in the room. I figured if I cut a hole in the wall just barely big enough for the a/c unit, anchor it to the wall and then put a big tote under it to catch the water drips it should be fine. I've found some 5000 btu window a/c units at the store for $100, which would be cheaper than a whole new fan/filter combo and would be able to keep the room in the 70's, hopefully. I was thinking of stealing the one from my front room and putting down there but my girl would probably get pissed, lol.

Also, I wonder if I do upgrade to the 8 or 10 inch fan/filter combo, how much would it drop the temps down. With the temps being in the low 90's would it have enough power to keep the room at 70 or even 75? Time to hit the internet to look for a cheap a/c unit.

Well, I broke down and got an a/c unit for the room. Within an hour the temps dropped from 96 down to 78. I'll check again tomorrow during mid day to make sure it stays low. I'm sure it will keep dropping over night, my guess is it will hit low 60's.

yeah the AC will do it, it cost more elec tho, honestly if you could have just got the temps down to 85 you would have been fine. thats why the fan route is better its not too necessary(just more ideal) to go down to 70s its just important not to hitting 95-100 every day.

calicat said:

More space equals more heat only if you do not exhaust the stale air being generated by your grow. Ever notice that in a small confined space takes less time to heat up than would a significantly larger area.

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I'm not arguing the amount of time it takes to heat a room. A smaller space may get hot quicker, but a larger space will eventually get just as hot if not properly cooled.

"Stale" air is not generated. Your plants simply rob the air of CO2, which needs to be replaced w/ a generator or a tank. As long as you're pumping in CO2 and using an A/C, you never have to vent out any air.

JayJammer said:

I'm not arguing the amount of time it takes to heat a room. A smaller space may get hot quicker, but a larger space will eventually get just as hot if not properly cooled.

"Stale" air is not generated. Your plants simply rob the air of CO2, which needs to be replaced w/ a generator or a tank. As long as you're pumping in CO2 and using an A/C, you never have to vent out any air.

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Unfortunately I don't have the luxury of Co2. I've looked into some of the DIY Co2 but I don't know which route to take. I would love to have a few tanks full of Co2, but who wouldn't. I've read a little about using the yeast and 2 liter method with tubing, but seems like too much work for how little Co2 it puts off. Has anyone tried it before, or does anyone else have any cheap ways of producing C02 to pump in the room.

noxiously said:

Unfortunately I don't have the luxury of Co2. I've looked into some of the DIY Co2 but I don't know which route to take. I would love to have a few tanks full of Co2, but who wouldn't. I've read a little about using the yeast and 2 liter method with tubing, but seems like too much work for how little Co2 it puts off. Has anyone tried it before, or does anyone else have any cheap ways of producing C02 to pump in the room.

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I feel ya nox, but you can produce some beautiful plants without supplementing CO2!

I have personally tried the yeast/sugar method and it made no difference. I mean I understand the science behind it but it just doesn't produce a consistent or high enough concentration of CO2 to give the plants that boost. I think the most drastic increase in growth occurs when you hit the 600-700ppm mark. Anything higher than that will still benefit the plants, but not as dramatically.

Anyway, have you got your exhaust sorted out?

JayJammer said:

I feel ya nox, but you can produce some beautiful plants without supplementing CO2!

I have personally tried the yeast/sugar method and it made no difference. I mean I understand the science behind it but it just doesn't produce a consistent or high enough concentration of CO2 to give the plants that boost. I think the most drastic increase in growth occurs when you hit the 600-700ppm mark. Anything higher than that will still benefit the plants, but not as dramatically.

Anyway, have you got your exhaust sorted out?

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Yea, I got it all fixed now, atleast I think lol. I bought a window a/c unit earlier and stuck it in there. Within the first hour the temps dropped from 96 down to 82, and after the lights were off for half an hour the temps dropped down to 76. I just wonder what they will be tomorrow when the lights are on again. I imagine it shouldn't go above the 82 mark since they did drop down that low after an hour of running. I'm going to keep a close eye on it tomorrow keeping note on the different times of day and recording the temp to see how it's doing. I'll upload some pics of the room here in a bit so you can see what I'm talking about.

Yea, I wondered that about the yeast and sugar Co2. It just didn't seem like it would produce enough, unless you are growing in a 2x2x2 room and you have 10 2 liter bottles going. I read somewhere about the 600-700ppm that you mentioned and that's what they were saying too. That' is the "butter zone" for Co2. If I remember correct, outdoors is an average of 300ppm, and at 2000ppm the plants start to burn, and 5000ppm is death. Not sure if that is death to humans or the plants, but I can imagine it would do some damage to humans since the outdoor average is 300, lol.

Ok, now the room looks a little crappy since it's not all the way finished, but it's getting there. I also moved the NFT system over so I could fit the Early Girl under the lights better. Once I finish painting, and shaving down the expandible foam in the cracks it will look much better. I filled the gaps with the foam since it's cheap, pretty well light proof, and well, it expands lol. That's what happens when you buy cheap wood that's warped a little lol.




Just a small shelf I put up to help hold the nutes and other things that I may need.

This door is to the left of the entrance and it leads you to the veg/clone room.


This is the smaller veg/clone room. It's still a work in progress, I do need to take the blueberry bush outside and plant it, yes it's a real blueberry bush and not the "blueberry" that we may like better.

Temps about a half hour after turning the a/c on.




If you can see it, but I put the a/c up to the top left corner of the room for two reasons, one is cold air sinks so I figure once the air is sinking the fans are lower and they should help distribute the cooler air, and two, I have the fan/filter combo in the opposite corner, front right, but you can't see it in the pics though. I figured with them being at opposite corners and the two fans blowing it should help pull that cooler air across the room, past the plant/s and the lights in hopes it would cool things down better. I also have two vents in the back at the bottom to help pull fresh air in and one in the middle at the top right above the door to help exhaust hot air.

Looks good! How long do you veg?

co2 would only make things worse. i have 2 tanks and they are off for the summer its even harder to control temps when your trying to preserve your co2 by no venting.

Well, as for vegging, it all depends. If I'm doing a scrog I tend to veg longer, typically around two and a half months if started from seed so I can fill up half of the screen then I flip to 12/12 and fill the rest while it's stretching. If I'm not doing a scrog I typically let them veg for 1.5 to 2 months from seed. But really it all depends on the size of the plant. I don't really follow a certain time frame, I just wait until they reach a certain size then I flip to 12/12. Most of the time I let them get to 12 in. then I flip them. I made the mistake once of letting them get to 20in before flipping and I barely had enough room and burnt the tops on a few, but I was able to salvage them without any ill effect.

I usually let them flower 7 to 8 weeks depending on the strain and how they are coming along.