Hot time, summer in the city... Suggestions on optimizing ventilation?

Pretty fresh to growing-- I've been tweaking a few things each week, starting with a pretty shanty setup. ~@Week 6 or so of veg, just upgraded from T5 [2', full spectrum, 2x 3500 & 2x6500 bulbs] to a 600 W HPS in a sunleaves reflector, w/glass, ready to install one of the 2 exhaust fans I've got to carry heat away from there, just not sure exactly how to make the most of my exhaust system. Other than those two little fans [5" diam., 80/105 CFM] I have been using a 12" desk fan, mostly pointed inward at the tent floor when i'm here and the door is open. I won't be able to do that during flowering when lighting is an issue.

We're working with ~ 4' x 2' x 6' tent with plenty of velcro-shut vents and full zipper doorway, situated snugly in a closet directly facing a standard doorway.

Before the tent I had installed a mylar door to allow to keep the closet door open for ventilation during the hot daytime. That's rolled up but readily available. Planning on switching to 12/12 and having the light period during the night when temps drop a little.

Just went out for a few hours and left the A/C in the room on high [pretty small bedroom], with the tent completely open with a 12" desk fan on high pointed up at the HPS hood, and closet door just open a crack. Temps got up to 95%, and it was only about 76 outside @ that time.

Short story long-- Wondering if I should vent out top to the closet floor tent side through carbon filter & in through exhaust fan via white dryer exhaust tubing into a lower vent hole, or if its worth it to attach the open ends of the in/outtake ducts to the makeshift mylar door, outtake at top and intake @ bottom. Also, since the air is being collected from the intake @ the roof of the tent, does it matter if that duct exhausts to the floor? I could hang the carbon filter horizontally in the tent easily. Does it matter if the carbon filter is exhausting to the inside of that small closet rather than into the bedroom? The window A/C unit is across the room, about 7' from closet door. I've been looking into homemade swamp coolers. Any help would be appreciated. Thanks.

Oh, also should ask:

-- Should I use two small fans ducted to mylar doorway for exhaust, one pulling air from the enclosed reflector [600W HPS running @ 75% power right now] and one pulling air from tent interior ceiling via duct hole, out the side, and through carbon filter on the closet floor, inside the mylar door, and then cut a hole at the base of the mylar door to rig the desk fan up for intake, probably making a cardboard "frame" around it to better seal the connection into the closet. For this I'd have to leave the tent open, at least partially, inside of the mylar door. I can partition the carbon filter toward the corner, or put it inside the mylar door and outside the tent, close to the air intake. That would cool the air pulled off the ceiling, right? Or is that flawgic?

Also, if tent-closed, HPS-on, evening temp is getting up to 95 with no exhaust fan on, will one fan, in line with the hood, and exhausted through the filter, be enough exhaust? The CFM is adequate for the tent size air quality, but will just one fan carry away enough heat, if my bedroom is around 80 ambient? I'm just trying to optimize things. The heat has been slowing these ladies down to much. Thanks for your help. Sorry for the extensive details--not sure what's most important to mention. I'm growing in soil, 3 x 5-gallon pots, and a couple of smaller pots. I wanted to square off decent conditions and let them veg more before starting flowering, but they're mostly showing preflowers, and i'm anxious to get this show on the road, you know? Thanks one million.

in order to successfully cool a grow you need to remove the hot Co2 depleted air as far away from your grow tent as you can then bring in new air.


Whats above the closet?

Can you cut holes in walls/ceiling?


LINK BELOW to my closet setup which may help you understand whats needed to run a 600w HPS.
https://www.rollitup.org/grow-room-design-setup/441212-my-new-closet-re-design.html




J

Been a while.. hard to tie me down to the internet in the thick of the summer...

The setup's evolved a bit. . . Small tent ~3x2x5' [30 ft^3], exhaust fan ducted from carbon filter atop tent, through 300 W HPS, out tent to room/closet when door closed, but this makes a bit of noise [connection between fan and hood must be shanty--but still too hot in there even when it's running; ventilation to the attic is ultimately necessary]. Small room fan, ~10" diameter, hung @ light level [uppermost point of fan @ glass level]. I leave half of the tent unzipped/open, for this exhaust to escape.

Really want to duct through closet ceiling to attic above, but I'm renting and need an easy repair.
However, once I noticed the 3" exhaust holes plugged in the attic, sets of 3 above two separate closets in the house but not mine, it's hard to think I couldn't pull it off.
Between the ceiling and attic is what I think to be 3-6" of insulated dead zone/plenum. Haven't investigated too much due to some seriously aged insulation in there. This opens up into a very large and empty attic with windows at either end, usually shut but I could open them for a bit of a crosswind. Holes above my closet would emerge about 8' from the eave at the edge of the attic, exposed to the outside, that's a possibility if a vent-line is necessary]. Closet ceiling is drywall, attic floor is 4" wood paneling. Any suggestions? Thank you kindly.