Lumens Per Squarefeet

Discussion in 'Basic Growing' started by Mr. Ganja, May 3, 2006.

  1. Mr. Ganja

    Mr. Ganja Registered

    What's a good rule of thumb for lumens per square feet?
  2. Swizzy89304

    Swizzy89304 Registered+

    You want at LEAST 5,000 lumens per square foot for a decent plant, although with mylar, you may get away with 3,000 - but dont expect brilliant yields, plus the buds will be fluffy and not that potent. Also it will take longer to veg and flower, and youll want to harvest the top of the plant first, then the bottom, unless you use some CFL's to light the bottom buds.

    7,000 will give you some damn potent bud, but youll still want to harvest the top first then the bottom, unless you dont mind having some fluffy bud thats not as potent as the main colas. It will also be quite dense.

    10,000 lumens is what you want ideally, IF you can control the heat, humidity etc. With 10,000 lumens per square foot, you can harvest the whole plant at once, with no noticeable difference in the potency of bottom buds - although they will be a little bit fluffier unless you get some extra lighting in for the bottom. Youre looking at rock hard buds, and it will be as potent as the packet describes. Also, you may be able to harvest a little bit earlier than normal, but only by a week at most.
    Dont bother with anything more than 15,000 lumens per square foot, as the extra light is unusable by the plant. It can only absorb a certain amount, plus youll have to take care of the extra heat and electricity costs. For closet/stealth growers, either a 250w or a 400w MH/HPS will do the trick. Anything more than that and youll be wasting your money.
    Last edited: May 3, 2006
  3. LIP

    LIP Banned

    As many as poss
  4. Kush Over

    Kush Over Registered+

    LoL. You just made me have an idea..

    "As many as possible. All right!"

    I could imagine someone trying to place a kilowatt of HPS on a square foot of space almost right up to the bulb; then try to put a fan between it and the light to solve the 'heat' problem only to come to realize it's actually the intensity of light turning the once green plant into a tanned pile.

    As many as possible is right, but there is a limit. Although I doubt this scenario is remotely possible [ no one's that stupid ], it's still in the realm of possibility.

    LIP and Swizzy are both right. Simulating the same environment the plant receives outside, light wise, is a good start with any grow.

    The Earth-Sun distance tells us, on a cloudless day, that there will be roughly ten thousand lumens per square foot at ground level. Let's try to get as close to that number as possible, but don't exceed it by much -- that is, don't put more than maybe 12k lumens per square foot or there's a chance you're going to bleach the plant, and 12k may still very well be too high.

    I've got a 150 watt HPS that can and will bleach parts of the plant that are immediately under the 16,000 lumen bulb [ well, 13,500 mean lumens ]. The damage isn't a result of the heat so much as it's a result of just being, well, bleached.
  5. LIP

    LIP Banned

    Well, your very right. Dont want too mant intensities. I supose if you had a 1k HPS you'd just have to have it about 5 metres above the plant lol!
  6. bongerstonerd00d

    bongerstonerd00d Registered+

    Just wonderin

    I have done a great deal of reading, and I have yet to see where it was suggested that you have 10,000 lumens per sq. ft. That would mean to have optimal growing conditions you would need 1000 watt HPS in a grow cabinet that measures 4 x 3.5 feet, roughly. Damn, how the hell would you keep that cool? If 10K per sq. ft. is the number, then all the hydroponic sites are dead wrong on their suggested coverage area per light, and advertising falsely. I wish some of the other experienced growers would shed some further "ight" on this (no pun intended).

    I am just a noob idiot, but I love to read.

    peace all,
  7. Kush Over

    Kush Over Registered+

    Well, if you're looking to produce optimum growing conditions, you'll follow Mother Nature's example with the Earth-Sun distance. I myself use several thousand lumens per square foot, and I can still see room for improvement.

    Cannabis requires a lot of light -- as much as we can provide. This means that we'd need to replicate the environmental conditions seen outdoors -- 10,000 footcandles/lumens per square foot on a sunny day. Three thousand, like what is suggested on some cannabis cultivation sites, is minimal and typically produces lower yielding plants of sometimes questionable quality [ i.e.: less dense buds ].

    And a 4' x 4' SCRoG/SoG space under a 1000w HPS/MH isn't unheard of, even in cabinet grows. The key is ventilation, which includes good intake and definitely good exhaust, especially around the light.

    Air-cooled hoods, anyone?
  8. bongerstonerd00d

    bongerstonerd00d Registered+

  9. Swizzy89304

    Swizzy89304 Registered+

    Erm... hes being a smartass by teaching you something new (telling you that you need fresh air coming in and the hot, old air going out) in order to maintain decent temps?
    To me it looks like hes teaching you something... to which you start whining and being bitchy at him. Jeez, smoke a spliff, chill out.
  10. Zandor

    Zandor Registered+

    The goal is to give the plant 10,000 lumens of the proper color light for the plants life cycle.
    That said there is nothing wrong with more lumens either.:D

    You can argue how you get it 10,000 lumens but that does not change the minimum goal.
  11. Mr. Ganja

    Mr. Ganja Registered

    I will aim for around 4,000-5,000 in my planned flower room. Thanks.
  12. Swizzy89304

    Swizzy89304 Registered+

    Will be excellent for a first grow. Ive got 7,000 lumens per square foot from a 250w HPS, and I would still use the 600w HPS but the heat that it generates just isnt funny. In the winter it would be fine, but my room would be bloody freezing because Id have to leave the window open. Get a few sheets of mylar aswell if you can, its dirt cheap if you shop around and worth every penny/cent.
  13. Mr. Ganja

    Mr. Ganja Registered

    Well, I wont be growing right now, but I'll be getting a house in about a year. Right now I'm just doing my homework and making blueprints. And I've got some money saved up solely for growing. I'm gonna devote a basement room to growing. A 10 x 10 x 8 should be good. I'll make partitions with wood, so I'll have a flower room, which I'm aiming to be around 25 square feet. The Veg room will be slightly smaller.
  14. bongerstonerd00d

    bongerstonerd00d Registered+

    Sounds nice, Ganja

    My flower closet/room will be 8'x4'x8', and my veg is going to be 4'x4'x8' high. I plan on having a clone cabinet also. Will you be using hydro or soil? I am hoping I can fit a 24 pot ( << this one in my flower room/closet. If I cant get all 24 in, I am figuring I can run at least 18. Pots are only 9 inches in diameter, so it'll be close. I guess I'll go with Super Sun 2 1000 watt HPS (2 of them in flower cabinet). That will give me around 8100 lumens per sq.ft. I figure with 18 pots I can get at least a pound per harvest. Space is not an issue with me, I live alone in a 14 room house, but I am going to use a spare bedroom I can close and LOCK the door on.

    good luck when you get started,
  15. latewood

    latewood Banned

    your question is vague...:) Even though you have been answered...Did you get the answer you were looking for?
    What are you asking? do you want to know the minimum lumens per sf necessary to grow under?
    Or, Do you want to know how many lumens to equal the sun's Output?
    what rule of thumb are you asking about?:confused:

    Glad to help, but didn't know what to tell you. lw:smokin:
  16. LIP

    LIP Banned

    My grow room is no where near my bedroom, but the lighting in there is SO hot it basically warms my whole house.. I havnt used the heating in ages.
  17. bongerstonerd00d

    bongerstonerd00d Registered+


    Got my answer bro. I figure if I use the 2 1000 watt lights I will have enuf lumens per sq. ft. (32 sq. ft.)

    Lip, I am going to be venting my heat outside bud, I have existing duct work that comes from basement I use to vent furnace with. I can easily tie into that with little problem. Will actually make furnace vent better because it will cause a draw since I am blowing the exhaust into it. Will check for outside noise, and if needed, I can add mufflers on the fans. But I am figuring (and this fucks me most of the time) but due to the length of the run, and I am going to use insulated duct, I should not have a noise problem.

  18. latewood

    latewood Banned

    the hydro lighting co's are telling you the maximum coverage area for a particular light with a reflector
    1000w...8x8, they are not telling you that you are equaling the footcandles per sf. that the SUN puts out.

    gotta go...will check back later. lw
  19. Krogith

    Krogith Registered+


    i don;t know how anyone would grow with out venting it dude =) the cooler it is the more nutrishion your babys eat :smokin: the hotter the more water they go throu:smokin: Lip my be heating his house but his babys i bet could use more Co2 than Stale air:smokin:
  20. latewood

    latewood Banned

    Hellllll yeah...2-1000's...I like Zandor's answer...

    If you want a real good lighting read. Aside from the good
    info here @CDOT...then go to Weedfarmerdot.

    I have 2 1000's in my flower room now 1mh agrosun gold
    1hps eye horilux. that is as close to the sun as you'll get I suppose. goodluck lw

Share This Page