its box built in middle of room in basement intakes are by the floor exhaust is into the room but out top of box.. all walls are plywood except the one that i open to do stuff inside is just a sheet of panda poly with a tarp zipper to open/close it duct taped all around except the bottom is velcro.

heat has never been an issue its just that the negative pressure/suction sometimes loosens the duct tape holding the "door" up that leads into the box. box is 60inx48inx72 in and is raised about 10 in off ground so inside space is only about 60x48x62 (lxwxh).. i havent been able to find any 12 in circular duct or elbows at home depot so that is why i ask about light proofing a squared cut of 10x10 in or any other dimension equaling 100 sq in

hope this clears up my problem, if not let me know what you need to know
bloodbrother Reviewed by bloodbrother on . Ventilation question Ok so I was reading rhizomes (i think) beginnerguide pertaining to ventilation just now and read that a rule of thumb for intake area was CFM of fan*.05 sq inches. Right now for a 450 CFM only 2 6 inch openings are present which is roughly 60 sq inches which is WAY less than 225 and there is negative pressure/suction inside the box.. so obviously adding more intake area is required but how can I do this and make it light proof at the same time? I mean for the current situation there are just Rating: 5