How would you cool this room? I need to step up my HVAC

Glaucksbacon · May 26, 2020

Hey all, I'm looking for some advice regarding my shed setup: I have one flower 4x4 tent and a veg 2x4, the veg is lit by 3 vero cobs with a max of 265w or so, and the flower tent is lit by two of the same light setups. So less than 1000w total, which is why this is so frustrating, it should be pretty easy!

My issue is that it gets hot as hell, despite my two 420cfm fans exhausting each tent. The flower exhausts straight outside via some ducting, while the veg exhausts into the shed. I have a shit 5k btu I think AC floor unit that basically pulls in more hot air than it can cool. One hose so it sucks through all the cracks.

The issue I have is that I only have the one window to exhaust out of, which is pretty full once the intake and exhaust are installed. So I can't really install an AC window unit unless I supplement c02. Cutting a new dedicated AC hole isn't an option either. Outdoor temps are only set to go up and I'd love if someone had a solution for me.

Do I reroute ducting so that the veg is pushed outside/turn down lighting/hope and pray over the summer? That would require some more ducting and a T/Y junction, right? I'm worried about backflow in that scenario.

and/or

Bite the bullet and get a window AC unit, ditch the intake and exhaust, and run sealed co2 during the summer, knowing temps will get into the low 100s outdoors? Or can I get away without co2 despite no passive intake? (doubt it)

Decisions decisions...

Thanks in advance for taking the time and getting back to me with any advice you can offer.

Glaucksbacon · May 29, 2020

Well, I bought a wye and installed it, so I got that going for me now. It seems to have helped temps a bit but we shall see in July.

Fixer · May 29, 2020

I'd install the biggest air conditioner that fits in that window.

St. Phatty · May 29, 2020

i'd reduce wattage in the summer.

just had to do that myself for the veg room. re-set the 250 watt Metal Halide so it runs from about midnight to 6 AM, then the 10 watt LED comes on, from 6 AM to midnight.

one option is to accept a slight reduction in output and to turn off the veg light for the summer, part of the time. So it's more of a batch system.

or if you have the discipline to move the plants every day, you can give veg plants a small amount of space in the flowering room, and move them somewhere to the floor below a window, when flowering has lights off. somewhere that doesn't compromise stealth but keeps the light schedule for the veg plants.

if there is any concern about LEO i would try to see how the room shows up on infrared. the exhaust from the fan & AC is hot air that can make an IR scan go "Ding Ding Ding". it stands out unless 1/2 your neighbors have AC.

Gry · May 29, 2020

I would be inclined to frame a new opening and installing a small window banger.
As to security people AC dog houses anymore.
Doing day for night helps me quite a bit.

Glaucksbacon · May 29, 2020

@ Fixer - What would you propose I do with the exhausts, thought? The window is super small, it's a 9x9 shed if I didn't mention that. Now I'm thinking completely removing the glass for more area to work with...hmmm...

@St. Phatty - Yeah I've reduced the wattage maybe 25% or so. I don't have the discipline to juggle plants back and forth unfortunately. No LEO concerns thankfully.

@ Gry - believe me I wish I could put another hole in the wall! But it's not an option, unfortunately.

Peacefrog · May 29, 2020

Definitely run lights at night if you can keep things lightproof during the day. Your grow room temperature will be determined by ambient temperature outside if you aren't cooling it. It doesn't matter how much intake/exhaust you run because you won't get cooler than ambient without AC plus you will have radiant heat from your fixtures that will increase temps. You are better off running a sealed environment with window AC and no intake/exhaust from the shed. If you keep bringing in hot air the AC will get overloaded so you have to recycle and cool air inside the shed. Use your fans to pull hot air out of the tents into the shed and let the AC cool the recycled air that will get sucked back into the tents. It's doable with LEDs but you may have to add some insulation or at least make sure you keep the AC intake filter clean. Exhaust as far away from the tents as you can and point the AC vents at the tents.

If you are getting over 100 in July you have to run AC or your plants will wilt even in the dark. No way around it.

Edit: A good window AC will suck up a lot of amps so be aware of your load if you are running the AC on the same circuit as your lights. Humidity will also increase in a sealed environment so you may have to combat that as well depending on where you live.

Glaucksbacon · May 30, 2020

@ peacefrog I would guess/hope that the AC would suck out a lot of humidity, not sure if I want to pay for both a dehu and AC running at the same time, yikes. It seems like my AC is keeping it at 60% unless its actively raining. The shed is pretty well insulated thankfully.

I know I'm asking for essentially a genie in a bottle solution so I want to thank everyone for chiming in and letting me bounce idea off of them.

Gone Camping · May 30, 2020

I'm a growage dude also.. about 6 years now. 9x18, 3x3 and 4x4 with options for HID and LED, mostly insulated and also one window.

I shut down late spring through early fall every year. I run a few smaller plants outside during this time. Been considering AC as i have a rear overhang that faces woods and is covered by roof overhang.. neighbors wouldnt see it. I'v considered c02 also but worry how much i would waste in a shed environment..

I'm in the Mid Atlantic area, having some time off away from the constant adjustments and oversight of the grow has become a welcome change while still producing a bit in summer.

St. Phatty · May 30, 2020

what is the temperature of the inlet cooling air at night ?

if you have some nice cool 60 degree air to deal with, cranking up the ventilation approach is worth exploring.

so much ventilation you don't need AC.

an air change every 10 minutes, whatever it takes.

you just need some powerful fans & blowers, which doesn't mean expensive.

you can use server fans, the kind that are obnoxiously loud, from Newegg. of course they have to be installed right.

i got a centrifugal blower from a surplus place in San Diego that was a serious air mover. Cost $15, ran on AC.

kritios · May 30, 2020

What about installing a controlled (dampered) exhaust high up in the shed? Run this exhaust during the pre-dawn hours to dump your heated air and pull in the coolest ambient air available to you. Add the window banger to get you the rest of the way.

Glaucksbacon · May 30, 2020

@ gone camping - I've considered shutting down during the hottest months, but I tried one outdoor as a test last year and I really am not great outdoor, I'm surrounded by farmers who spray noxious shit and all the bugs run to my organic free range yard, outdoors I got caterpillars and mites and the end product just wasn't that great, I ended up trashing it once we had more indoor. Not to mention if I went big outdoor I'd have to do a lot to shield my neighbors' view...and I live next to an airport the county police use...Its legal in this state but I'd rather not be noticed, I live in a red county.

St Phatty- The air can get that cool but can also get hot at night as well, I'm leaning the direction of stupid amounts of ventilation as it's so much more economical than turbo AC or co2. The problem I'm now facing is not enough air intake square inches, the intake air whips in through the cracks in the door and around the window insert, it gets hard to close the door as the wind pulls it so hard, sometimes it produces a godawful high pitched whistle, haha. I have a duct booster fan I can place on the right duct shown in the window picture I posted, that should help...

Thanks for brainstorming with me everyone, please continue to chime in.

Glaucksbacon · May 30, 2020

@ kritos I was considering something like that, a filtered main exhaust in the shed proper with the two tents exhausting naked into the shed, maybe ducted right up to the filter. I was really hoping to not have to spring for a better AC honestly.

troutman · May 30, 2020

If this is a shed, make in air inlet hole on shaded side near the bottom to allow cooler air in.
The exit should be on opposite side as high as you can put it. Inlet and outlet should never
placed side by side. Running the lights at night may help a lot.

Glaucksbacon · May 30, 2020

When people say "run the lights at night" what times does that typically mean? 8-8? 9-9? What's the sweet spot?

Mr. J · May 30, 2020

Glaucksbacon said:
When people say "run the lights at night" what times does that typically mean? 8-8? 9-9? What's the sweet spot?

Well obviously it means the half of the day that is cooler than the other half of the day. You would need to figure out exactly what that is for your specific situation.

Glaucksbacon · May 31, 2020

Yeah that makes sense Mr J, I was hoping there was a catchall rule of thumb lying around so I don't have to look at historical weather tables. I'm running 7p-7a right now but I think I can push that back for better results.

Fixer · Jun 1, 2020

Glaucksbacon said:
@ Fixer - What would you propose I do with the exhausts, thought? The window is super small, it's a 9x9 shed if I didn't mention that. Now I'm thinking completely removing the glass for more area to work with...hmmm...

I wouldn't worry about exhausting the shed if it's cool enough and you can control the RH. If you can get an AC that is big enough to handle the load in the window, I'd throw a 50-70 pint dehumidifier into the space and run the system closed. If the window is too small to accommodate the appropriate sized AC I'd frame a new opening in the wall for an AC or install a mini-split. Of course all of that cost money.

Glaucksbacon · Jun 2, 2020

Thanks fixer, unfortunately I'm able to grow in the shed, but my (relatively cool) landlord isn't cool with modifications, I have to work with the one window I have. I'll probably end up reporting back later as the summer heats up.

Fixer · Jun 3, 2020

Put at least two inches of rigid foam on the ceiling. You can hold it up with relatively few screws. Take it down when you leave and patch the holes if they'er in sheetrock. It will keep heat out in the Summer and in in the winter.

By running you lights at night you have less cooling demand when it's typically hottest and you use electricity at off peak rates. It won't make much difference with 350W but I save about 20% by running at night.

How would you cool this room? I need to step up my HVAC

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