a sealed room .......bad u need air flow to keep the temps down for the plant and to add co2/cooler air
and yes i line both the floor for the fact of reflection to bottom of leaves (little as it is might as well get it ) and u can use a small transparnet dish add little water on there it will increase the humity some 5-7%
and the roof just becuase i am paranoid and kept me out of trouble for 11 years now .....never know who is flying and what they are using
your going to need a intake and a exhust system if u own the place go tho the ceiling to the attic.....if in a area where u can have the smell u are golden if not then u can place the carbon filter and fan up there keeping the noise to lowest lvl u can using this method with out needing a muffler
as for a intake can i say look into a cat door (for doors) take the flap out and fit a fan .......if u use a black carbon mat it will reduce most of the light coming out and it filter the air going in to keep mold and bugs out ............if u ever move i take the door with me