why is the grow room so hot? any suggestions on how to effectively lower the temp?

I have roughly about a 4'x4' grow space where the temp reaches around 90 degrees with the door closed. The door has been left open, where the room stays around 82. I recently bought a 165 cfm inline fan to try to lower the room temp. Since I didnt want to drill a 4" hole in the wall i have run the duct underneath the bottom of the door (which still has over 1" of clearance from the bottom of the floor). The problem is that they are about to be put into bloom and with the temperature being so hot with the door closed, I'm left wondering what i should do

my best bet is you light is too strong in such a small area acting like a convection oven. add more vents or another fan possibly?

also the fact that heat rises could have something to do because the duct is under, not allowing the heat to escape but build up in the ceiling area of the grow room instead

Are you renting? Go to home depot, buy a cheap 30-40 dollar door, and cut holes in that door for ducting and the like, then hang it and just stash the other door...when it's time to move, or you have an inspecion or company or houseguests or something like that, just hang the old door back up and it'll look like you didn't do anything at all.

What wattage is the light?

it is a 400w HID, the ballast is in the top of the room, the fan is to the left of it about 4 inches lower with duct attached to the top and the bottom;the top sucking air from the area next to the lamp, and the bottom duct releasing underneath the door

Where is your fresh air vent? Maybe the exhausted air is being sucked back in.

so i need two fans?..i have a oscillating fan thats stands vertically and then the 165 cfm 4" inline, the inline is pulling air from beside the lamp, pushing it underneath the door; however, currently the door is open to keep it as cool as possible, its at 82, which isnt exactly ideal but i can handle it around 80, although id prefer it at 75

Is the crack under the door the only place for air to enter the closet when the door is closed?

yes, when the door is closed, there is only a gap between the floor and bottom of the door, which the duct also sucks air thru the top, down thru the bottom and outside the bottom of the door

So is it possible the hot air exiting the closet is re-introduced back into the closet? I ask this because since your evacuating air out, there must be a corresponding inward flow of air, and that air could be the original hot air.

the problem seems to be your set up. you need to focus on the path of your air. first find a nice cool place to bring fresh air into the room, maybe from outside (filter the air first) or maybe from another room, this is where you want your ventilation to start, run a duct from here to your growroom, you want your growroom intake at the base of the plants. your grow should be good with a passive intake, meaning you let air flow in your intake without a fan. an exhaust fan creates enough pressure to force air in through your intake hole. your exhaust intake should start as close to the light as possible as this is where most of the heat radiates from. run your exhaust to a separate area than your intake. this way you always get fresh air and exspell hot stale air. as previously suggested you can buy a cheap door that you can cut holes in. also it is not too hard to repair exhaust holes in ceilings and walls by saving the circle from the hole you cut and spackeling it back into place then painting over it once its dry.

Yes good things said here listen to them. Don't be scared to do some small upgrades to move air properly. Watch some youtube videos and you will learn how to fix minor cosmetic house stuff. Like one poster said go get a cheap door to do whatever you need to and save original door. Dry wall to that's easy work for patching holes. Unless you have wall paper but doubt that if you rent.

also try to keep your ballast outside of your grow area, ballast can get really hot and cause your growroom to heat up. in turn the lamp can cause the ballast to get hotter than the temperature it is made to run at causing it to run inefficiently

i moved the ballast to outside of the room, yet it hasnt seemed to lower the temp, it seems to have remained the same

move the ballast outside the room...

when i was growing in my 3x3x9 closet and using a 400watt hps it was also very hot ...
if i left the door closed it would get up to about 100 degrees ...
not good ...

it just didnt work out to good for me in there ...