My grow room

I am starting my first indoor grow. I have done plenty outdoor but with the weather down I decided to go indoor. I have constructed a 4x10 box and split it in two with 2x4s framed in the center to create a barrier between the box for two seperate rooms obviously one to veg an one to flower. I have Lined the frame of my room with thick black plastic on the exterior. The front of my room has two flaps(made of the same plastic, that velcro on so I can ease my way in an out of the room. My question is, Is the black plastic enough to keep my room in the right temp ranges? Should I line the interior with black plastic b4 I line it with mylar or will the exterior plastic be enough? also at the very bottom of my tent where the front velcros there is a gap about one inch between the bottom of my plastic flaps and the ground.This is a very small gap and the lights are not able to leak into the other room except for on the very bottom of the floor. The parts of the frame where i did not velcro leaves little spaces so it is not air tight as well.. is this ok? I plan on getting my plants this week so id like to perfect this room tomorrow... Thanks all!!!!