less space = easier venting?

ok well i can either sperate my 2 rooms at 2 points, one making the flower room bigger or one just closing off the flower room to 2x4, i have 2 places to hang a black sheet pretty much, right now the room is open and the sheet covers between the 2 rooms so flower is about 4x4 u think taking away that 2 feet and putting the sheet up closing the room off more will vent it better keeping the heat in a smaller area easier to vent?

i'm not sure how well a black sheet is going to work, the light will probably get thought it, get double sided mylar rolls - once side is black, and the other side is a very very reflective white, so it will seperate the light and reflect it properly