Exhaust questions in a hot climate

You'll need the AC...I could give you some tips and tricks based on using physics to help, but they won't be sufficient, alone. You still want to use negative pressure and SUCK air across the light and out of the tent, instead of blowing, but you'll need the AC.

RH will climb as temp goes down. If it's 90% humidity at 100 degrees outside, and you reduce tent heat to 80 degrees, your RH is going to be significantly higher...possibly enough to cause condensation issues, or even (I've seen this happen, it's cool as hell) cause a mild "drizzle" rain inside the tent.

So you're going to need a dehumidifier for summer. Or chill the air before it gets into the tent so it loses humidity...which isn't really feasible, reasonably.

You can help your tent in multiple ways....I can give you a number of "redneck engineering" solutions that would let you run your tent in summer, no problem...but it'll look like Jethro Bodine and a mad scientist got together in your living room to build your grow area...and did it while stoned as hell.


But it sounds like you're looking for a shopping list....here's what I'd go with, personally, with the limitations you've named:

5 X 5 tent...since it's a first grow, and either you'll repeat until this tent's trash or you go bigger, get a cheaper, but not CHEAP tent. You get what you pay for, don't buy a $100 tent, but don't buy a gorilla for $400 unless you know you're going to grow enough crops in it to be worth the investment.
I swear by the Gorillas, BTW...great zippers and seams, thickest fabric in the industry...they survive abuse.

A dehumidifier and an air conditioner or air cooler (again, can show you how to ghetto rig a chiller...or you can get a video on "building a redneck air conditioner" off YouTube. Only real savings in it is in initial investment, though...you'll end up spending enough on ice or dry ice to make up for that by your third crop). Get the AC unit if you're serious, not just trying it out.

Lighting...heat's an issue for you, you say. 5 by 5 tent. Go LED based hybrid. For a 5 by 5 tent, I'd go with a MARSII 1200 or 1600. They're overkill, but they have the most channels, use focusing lenses to intensify light at footprint, and have a decent reputation for reliability (and good quality components...been researching them)....but you can choose brand, yourself. What you NEED to keep an eye on in choosing LEDs is wattage of each diode/emitter (3 or 5 better than 1, even though less efficient on a lumen to watt comparison), number of "channels" (each channel covers a specific "little" band of wavelengths inside the broader deep-orange-to-near-IR and blue-to-near-UV useful spectrums. Any gaps left reduce the effectiveness of the LED compared to an HID (MH/HPS) system....but the LED system is cooler, uses less electricity, and provides light ONLY in the primary useful bands.

When I say "hybrid", I mean "don't just use one lighting system"...with LEDs I suggest a single 23/100 CFL in each corner of the tent, hung about a foot from the walls on both sides, hung high...you're just trying to add a little "tickle" to bandwidth gaps. Add a couple desert reptile UVA/UVB bulbs from the pet store...it helps.

Use a 250CFM fan or higher...with your anticipated temp issues, I'd say higher, but on a rheostat (dimmer)...better control of air flow while maintaining the ability to control heat better. DON'T be dumb and put a pair of 8 inch Windkings on full blast on the poor thing. Fine to sue them, but use a dimmer...lol.

Noise rules. Shaking is noise. Speed of vibration is pitch. Air motion is noise, the tighter the volume of the area it's being forced through, the noisier it will be. A larger fan at lower RPM is going to be quieter in "air noise"...but may result in louder overall noise at more noticible frequencies (lower RPM is more pronounced vibration, which means louder. Slower means lower frequency. Just like a woofer speaker, lots of movement in low frequency makes it boom instead of tweet). BOLT YOUR DUCT DOWN. Use weatherstripping for doors between any components so vibration isn't transferred as well (as in, if you use horseshoe bands to bolt your duct to a chunk of wood, and strap the wood tight to your upper frame, use foam weatherstripping between bands and duct, and between wood/hardware and tent frame. Put weatherstripping between the band clamp and the duct and the fan intake, before cinching it down). The more you absorb and negate vibration, baffle the air so it doesn't create consistent waves, and so on, the quieter your system will be.

Nutes...first timer, I would suggest Fox Farms' Big Bloom, Tiger Bloom and Grow Big trio...follow instructions. They're so easy an idiot can manage them while wasted. I STILL use them, for the most part, since I can't do "mix your own".

Research your soil. Nothing with pre-fertilized dry fertilizer in it. Some folks get results with miracle grow or fox farms soil, most complain about damage. Easier to buy non-impregnated topsoil that's already mixed with normal "organic" materials, no added nutrients, buy peat moss, pearlite, and such o mix in, yourself.

If you're not up to the research, ask some DIYers here on soil mixing, or at least buy organic soil without dry fertilizer in it. If you want, I'll explain the hatred of dry fertilizers. If not, we'll leave it at "They WILL burn some roots and starve others. Your plant will usually survive, and do OK, but why buy trouble?"

Test equipment...you'll need a soil pH test kit...and use it regularly until you know if your pH is consistent or not. If not, plenty of guys around here who can tell you what to add to make a lasting change, instead of fighting it back and forth. You NEVER want to make large changes quickly, or make notable changes too often (unless you establish a rhythm to them the plant is OK with...plants like consistency--you can have a 20 degree temp range on a regular basis, and they'll be OK...as long as that's either a consistent pattern or a one-time, short-term incident...but one day going from 80 to 60 over night, next three days maintaining 75-80, then two days of 75/55...plants won't be happy.

You'll need a thermometer and humidity meter inside the tent. Place as far from the dehumidifier as possible for the humidity monitor, thermometer, put as close to the plant most directly under the light as possible. You want to know what your WORST temp in there is.

You'll probably want to monitor CO2, but honestly, CO2 supplementation systems and meters are pricey, and not necessary until you know you do well in other respects. Just open the tent doors for half an hour twice a day until then.

I don't know if you intend to go with a scent filter, or not...a couple ways to do that, too...expensive carbon filters, or another example of redneck engineering that makes your house smell like you are a Febreeze addict, but works almost as well.






I miss anything, folks?

 

You could run an HID in a vented hood, intake and exhaust with outside air. That way you're not taxing your a/c as much and will get lower temps. Would require 2 inline fans though, one for your light and one for your tent.
 
a/c the room and keep it closed, if you can bring your room temps down to 75 or less I think you'd be good to go with a 1kw. Definitely get an 8" hood and fan though, I find my 6" to be a bit lacking in summertime.

 

Check out the ventilation sections on Just4Growers http://www.just4growers.com/stream/ventilation-and-environmental-control.aspx
 
Also go to the home page then look at other technical articles. I love it because they break technical terms into the "So What?" for laymen.

 

Are you able to run the exhaust ducting outside the room? Directly outside or maybe in to another room or an attic? If so I would use a 1000w HPS in an air cooled hood taking air from in the room. But outside of the tent, through the hood and straight out of the room. you would then need another exhaust fan with filter pulling air from the tent. I would then have the air conditioner in the room with the exhaust directed to the tent inlet vent. A humidifier might be needed but the air con might take care of that for you, mine does 
 

 

sorry to hijack but this is something along the lines of what I wanna ask since Im gonna be growing inside a tent with LED too.

Has anyone grown in a hot garage? I live in a desert climate, and a hot garage is the only place I may be able to grow. Im thinking I could keep a cheap window A/C and have that air blow into the lower intake ducting/intake holes(secret Jardin 2x2) and have an inline fan in there too for exhaust.

is that doable or will the temp outside the tent (in the garage) be too great to overcome?

 

I would build a stand for the a/c out of 2x4 and cut a window in the tent for better efficiency. Cut out a square a few inches smaller than the a/c and slit the corners to create flaps.

Window a/c removes heat from the air that it sucks in through the front grill, so if you're sucking in 90f garage air and expecting the blower to cool your grow to 75f it's going to work a lot harder than if you had it removing heat from the already cooled grow room air.

You will be able to bring that 2x2 down to whatever temp you want using a lot less electric.

edit: You could even get creative with velcro and some tent material, adding a window flap for the a/c that can be closed when not in use.

 

So you're saying like a giant/big intake the size of the blowing surface of the A/C? instead of the two intake ports?

 

That's how window a/c's are designed to work. If you are concerned with the garage air being too hot to overcome then this is how you overcome it, by reducing the load on the a/c. Saves money on electric too.

This is something I've researched and done on my own grow, not talking out of my ass.

 

The thermostat on your a/c goes off of the intake air. If you set it up the way you were describing, with the unit sucking in 90f air all the time, then it will run constantly even if the thermostat is turned all the way down. It's the most inefficient way to go about this.

You asked for people who have grown in those conditions with a window a/c, just offering my experience. No big deal, do it your way if you want.

 

Sorry if I came off wrong, I just didn't understand what you were saying.

Im still not really sure I understand after the pic. It looks like you're growing in a box type set up that you constructed with a wood frame and stuff like that, right? From what I've gathered you worked the A/C into the construction where it acts as your intake port? and basically all your in take is A/C'd cooler air that is sucked in from within the garage?.......or does the intake/other side of the A/C in the pic you posted suck in air from outside of your garage? Is the A/C sitting in a window you made to open to the outside?

Sorry I'm slow. If Im right, I can't do what you're talking about. Im growing in a 2x2 Secret Jarding tent, and don't think Im skilled enough to cut open the tent and make the A/C output inside/facing the inside of the tent.

 

If you have an AC in the room where you will place the tent, then just have your intake vent opening in that room. For the cf exhaust, and cool hood reflector exhaust, I wouldn't ever put my fans in my grow tent, they generate heat, so placing them in the grow area has never made sense to me. I have tested that theory repeatedly, and having (2) velocity fans inside a tent raises the temperature 8 to 10 degrees. Sure you can manage that, but why would you cool something that you shouldn't have to cool. For exhausting to the outside you can make a little exhaust box that will sit in your window sill that will allow you to just open the window 1 inch, with left and right styrafoam seals that will allow you to exhaust your cf, and cool hood reflector without anyone knowing you are exhausting anything. In all my grow rooms, all I put in there are cf, hood, and ventilation fan. I usually have 3 intakes, one for my passive intake, one for my humidity / dehumidify control, and the last one for my hood. Then I have 2 exhausts, one for my cf, and one for my hood, I pull air through my cf, and I push air through my hood. I push air through my hood so my fan doesn't die an early death from getting overheated.