So I have 2 seeds planted at the moment. One is doing beautifully and the other not so much. If it doesn't sprout here in the next couple days I am gonna trash it and plant a new one. So this was my first attempt at a grow box, but as you can see it needed to be much more inconspicuous and not let as much light through. And here she is now after some home depot runs, and this is with the lights on! (oh and as for intake and exhaust, i havent fab'ed that up yet, but i will soon - i have a fan running in the room though: pulley thing to lift lights up and down smoothly: Lighting set up for germination and the first few weeks of veg.
Nice looks good. When you setup the fans exhaust through or near the top and intake near the bottom of the box.
Looks nice. You should get some silicon and seal all of the seams in the back and then use weather stripping to seal the door. In the inside you should either line it with some reflective material or paint it with some flat white paint. I like your light setup. I'm about to make one really similar today for my dresser box.