Ventilation question

[bloodbrother]

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 4 6 in 90 degree ducts making it light proof. I need at least 2 10 inx10in square cut holes or something similar equalling total of 200-225 sq in. how can i do this without having to buy 12 in circular duct and keeping it light proof? any help would be grrrrrreat

bloodbrother Reviewed by bloodbrother on 11-12-2008. 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

[LuciferN]

I didn't read the guide you're taking about but I'm not sure you really need to have all that exhaust and intake for your setup.
What is the cubic feet of you're grow space ?

[bloodbrother]

5x4x6 1000W HPS air cooled with carbon filter... i had a 300 didnt do the trick

[LuciferN]

I have an 672 cubic foot area (12x8x7), an 1000W HPS and I'm using a 450 CFM with a carbon filter. So I don't understand why the 300 can't do the job, it may be an intake problem or where you exhaust...

[bloodbrother]

you can use a 1000W for that big of space? Well looking back maybe i should have got a smaller one but yeah what im saying is its an intake problem and i was wondering how i can make bigger holes while keeping them light proof so that i can reduce the suction inside the box... i mean there is no problem except that the poly door when shut is sucked into the space but still stays shut

[LuciferN]

This is the total space of the room, actually the grow area is more a 4x4x6.5 so the 1000w do the job... A picture of the setup could help, I'm not too sure how you made it...

[bloodbrother]

i mean this is a little off topic... im trying to find out how to lightproof a hole in a box that will be about 100 sq in... not question on fan size.. because i mean its said 3-5 times a minute so 120 ft^3 x 5 times per minute is 600cfm so 450 is about little less than 4 times a minute... main question is how to light proof 2 100 sq in openings regardless of my setup

[LuciferN]

Like I said I really want to help you out but I can't figure out how you're setup is done... An 90 degree angle pipe can help you get it light proof, some duct might also be a solution.

[bloodbrother]

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