Need advices to perfect my growbox

hello. so, i decided ima start growing indoor too. got a good closet, empied it, made new doors, lamp in, ventilation... its workin just fine, but i need some advices to perfect it. the only thing that conceres me are the temps. they are not too high, but some degrees less would be just perfect. they are at 26°c to 28°c(78f to 82f) with lights on. i want em under 25°c(76f), and can get em with the doors 1/4 open. so i guess its the ventilation.

so, lets go with the measurements. the cabinet is 90x40x130cm (3x1,3x4,2 feet or whatever)=0.5m3 (16.5cf? cubic feet) , exhaust is 190m3/h (111CFM) inlane fan, which is more then enough for the space and pasive intake area is like 4x the exhaust area. ohh, lamp is 250w hps in a cooltube, dutched to the exhaust fan. i have 2 computer fans in there, blowing from the bottom to the top. the balast is in there too, on the very top of the closet. it gets hot to the touch, but if i put my hand just close to it, it doesnt feel hot at all. if i put my hand under the cooltube, it feels hot, but close to the ballast, its not hot at all. so guess that shouldnt matter much, its on the very top anyway. so, what do u think, bigger intake holes would help? maybe puttin the ballast out of the box? no chance im gonna buy a stronger fan, so i have to make it work with this. ull see where the temps are measured and how far is the light in the pics.

no maylar or any reflective material in there either, and that is what im gonna ask too. should i put some mylar in there? im gonna lst it hard, so i guess it shouldnt matter much either.

ill cover the holes with some light traps. the plants are growing super, cant say anything, but would still like just a bit lower temp. humidity is 50%. thx for the help

getting the ballast out of the closet will help. i see your only taking air out through the light, so above the light near the ceiling will build up the heat and the fans blowing up are pushing the upper heat around. anyway to have an exhaust setup to take away the heat up high? ventilation is your key because you should not have to open your doors to get the temp you want. something reflective on the walls is always a plus. either mylar or panda film. flat white paint will work also. i like panda film.

i see what u mean. gonna put the ballast out first. if that wont help, guess ill have to make a little computer fan exhaust on the top of the cabinet. what about making the intake bigger?

it appears that the openings in the front of the closet should be big enough. i like to have a slight negative pressure inside the room. i use a bigger fan than you do. i have a 6" exhaust with about a 7" passive intake. i may make it an 8" passive intake at some point. the passive intake hole should be slightly larger than the exhaust hole. this may not apply to computer fans but more for inline fans like the vortex. with my exhaust running i can feel it suck the door in a little as its almost closed.
a pasive intake to large and you may not get good negative pressure. an intake hole too small will be too much negative pressure putting extra work on the exhaust fan.

so, i put the ballast out some hours ago. after 2h running, the temps are still same 26-28°c(78-82f), maybe 0,5°c lower. but if i open the door, after like 3min, the temp goes down to less than 25°c(77f). so tomorrow ima try to make a bit bigger intake holes. i dont really care for negative preassure, since i ownt use a filter. and anyway i can patch em up.

ohh and the temp should go down when i rise the light, right? at least in my case, more heat will be sucked from the top since my exhaust will be higher.

Add an intake fan instead of relying on passive intake.

good news, i hooked up a computer fan to the intake, and the temp stays at 26°C(79f). kinda stupid of me that i didnt think of it before. guess ima get another fan and hook it to the other intake.

another question... how should i run the ventilation at lights off? for now i just run everything, the exhaust fan, the intake and the fans inside the box. i dont care for the sound it makes, but was wondering if i should only run the fans in the box, not the intake/exhaust fans, to keep the temp a bit higher at night. thx for all the help.