Grow Room Design And Build

Just wanting to throw my rough design out there to see what you guys think about it. Im gonna be building it in a closet down in my basement to keep it out of wandering eyes view. My goal is to grow 4 plants at a time. Im not gonna do any cloning at this time but i may add another room next to this one and start to do cloning.

Just give me some feedback on things i should consider changing or look at modifying.

A couple questions i have....Im gonna run a timer for the lighting and should i have the oscillating fan hooked up to that to run while the lights are on? And then when they are off shut it donw? Also should i get another timer for the intake exhaust to clear it out every 30 min or so? I guess the main questions im having right now are the fan and air movement.

keep exhaust on at all times unless running co2, also keep your fan running 24/7.

You will also probably want to air cool that 400w hps

plant 8 beans, hopefully you'll get 4 girls

Would the Metal Halide be a good light to start the seedlings or would i be better of doing fluorescent id prefer to just do the MH if it will work out alright. Im gonna do 4 beans and if 2 are female im happy. Im going just for personal right now. So i dont need to do tons at a time. Plust i need to keep my space usage down.

How do you control humidity properly? Cause you want to have certain humidity at certain times of growing? I guess ive been reading that you need to have it at certain levels but it never talks about getting it into that level. Is it just the speed of the exhaust fan? Slowing it down will leave more moisture and turnign it up takes more moisture out?