Last question. I have decided on a 400w hps to lig...

A lot will depend upon the surrounding temperature, but I think that 400W will do bad things the few times that you can't open the tent every 2 hours. I recently switched from a 400W (old) HPS to 300W LED because of heat. I'm growing on my 2nd floor which doesn't get as good of AC as the main floor. The room will normally hit hit 27.5-29.5 C on warm days, and before when I was exhausting from the tent into the room, the room got to 32+C and the tent was 34C. Now I'm exhausting out the tent to the window (I cut a piece of solid foam insulation board (cheap) to fit my partially open window and cut a hole for the duct to go into), and the room's back to 27.5 and the tent is 28.5C. Back when I used to grow in a basement, I ran my 400w HPS in a 4'x4'x4' rigid box I made (and wow was that 4' height a challenge!). Even in the basement in such a small space I needed to exhaust heat from the box. Exhausting heat into the rest of the basement was fine even during the summer. I was able to get a cheap (but loud) used bathroom fan to exhaust the box - maybe check your local classifieds. If nothing else, there are cheaper "duct fan"'s that will help, even if the amount of air flow won't be much, and they'll wear out faster than an inline will.

hi dude ! hard to be plenty affirmative without having seen your installation.... extraction in a closed room has 2 important roles : firstly dissipate the heat that can accumulate in your room (especially with Hps) 2ndly bring fresh air loaded with new co² : absolutely essential for photosynthesis so for the good growth of your plant. I recommend you find a solution.... at minimum....cause open the door could be not enough....depends of how many times you can do it 😵 Hope this help 💪

hps with no wentilators burn ur plants and drying everything. better buy LED

I just installed bitcoin miners in the window to bring in fresh air but there not cheap. You probably won't have a temp issue, but blowing on light will raise the temp. Blowing on plants lowers. Just have to find sweet spot for fan. Open the doors if gets too much

It depends on what Is outside of your gardening room. If you can keep the temperature outside the room lower it might work. I strongly recommend fresh air in and out for for ladies. My first grow I attached dryer duct tip my fan to get air flow. Best of luck

When I was in the same situation, I left the door open 7/24 and put a good ventilation fan right outside the tent,blowing air from outside to inside.This way I didn't need an extraction fan.Temps were ideal.If your conditions are suitable,you can leave the door always open.You won't lose yield no worries.that doesn't make a noticeable difference.

fans only blow the air that’s in the grow room around the room so without a extractor I don’t think you’d be able to keep the temperature down enough. Unless it’s very cold where you live. My 400w hits 27c occasionally more with a 4” extractor and a fan blowing 24/7.