Covering a 3 x4 meter space

A question from a fellow grower:

I have some question and would be grateful if you could answer me.
What is the best choice to cover a space of 3 x 4 meters with LED lights. How many and what kind of light (what watt)?
Of course, Please consider that room is in house and should be amount of empty space between each row of plants that i go between them to do their work.
In general I would be grateful if you guide me to design a room with dimensions of 3 x 4m with full details including: carbon filter, exhaust fan, inline fan, what kind of Smscom or GSE controller and etc.

For LED, you want 25 TRUE (not “equivalent” but actual wattage consumption) watts for every square foot. So 3’ x 4’ = 12 square feet, times 25W, so you’re doing to want a 300 watt LED. I use the MarsHydro line, they are good quality lights, and cheap, so you can get one of their “300W” lights (that’s “equivalent” wattage, actual wattage draw is about 140W) for $70 on eBay. Two of those should cover 12 square feet just fine. They also sell a “600W” light (about 280W true) for $140. Other good choices for more $$$ are Platinum LED and California Lightworks.

For ventilation on that size of space, I’d go with at least 6" duct fans, 8" if you don’t mind spending a little extra. I’ve got 4" fans for an 8 square foot space, and that’s pushing it. One fitted with an inline carbon filter at the TOP of the tent/room, blowing OUT, and the other at the BOTTOM blowing IN. Also, another small fan or two to sit inside and circulate the air.

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Hi dear friend,

Thank you so much for your reply.

Is 25 W really enough? And other question:

Are full spectrum LED lights enough for all stages or is it better that I use growing special LED for growing stage and flowering special LED for flowering stage?

How much is yield difference between them?

Best regards

Obviously, I’m a dumb American! I just now noticed you said METERS, not FEET! So 3 meters is about 10 feet, and 4 meters is about 13 feet. That gives you 130 square feet, meaning you’d need about 3000 Watts to cover that entire space! That would be a HUGE grow!

However, just because you have that much space doesn’t mean you need that much light! You can buy some cheap reflective material like panda film, or I even just use a couple of those mylar reflective, fold-up shade thingies you put in your front car windshield to keep it cool. Just hang that around your plants, and you can make your actual grow space within the room however large you like.

For future reference, however, 1 square meter equals about 11 square feet. So technically, you need about 275W of true LED per square meter.

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As far as lighting for veg and bloom, yes, technically, blue spectrum light is better for veg and red spectrum is better for bloom. However, as long as its within the spectrum between 2700 degrees Kelvin color temperature (red) and 6500 degrees Kelvin (blue), you should be okay. The wattage is much more important, you can grow start to finish on red OR blue light, but only if you have enough Watts! If you’ve got the money, I’d actually recommend the California Lightworks LEDs, in addition to red and blue spectrum, they provide UVB as well, which is supposed to increase THC production.

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Thank you again of your full explanation.

Is it better that I divide the my room into small spaces, for example 2x2
or 2x3 foot and use a lot of less power LEDs in side by side or large space
for example 3x4 or 4x4 or even 5x5 foot and use a few of powerful LEDs?


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Hey, if you’ve got the cash to spare, this is probably the best light out there for 1 or 2 plants. Just remember the MarsHydro will do just about the same quality job for about $70, as opposed to $400+! :wink:

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Just to make the most of your lighting, I’d use one space for however many plants you choose to grow at one time. However, if you can install some lightproof dividers or walls within the space, I’d divide it into 3 sections, each with their own lighting. A small space for a mother clone plant, kept on an 18/6 light cycle, another small area for developing and rooting clones, kept on a low level light cycle, and the large flowering area, kept on 12/12. That way you could have a continuous grow, and harvest new buds just as fast as the new clone cuttings can grow on the mother plant! :slight_smile:

One final note, think of lighting and space in terms of output, not number of plants. In other words, in a 2’x2’ space, 1 plant will give you just about as much bud as 2. Does that make sense? So if you’re just growing 1 plant, you could grow it straight and tall, and it’d just take up 1 square foot of space (and produce about an ounce of bud). However, with the same plant, you could top it, crop it, and train it into a SCROG that occupies an entire 4’x4’ area before you switch it over to flower (and produce SEVERAL ounces of bud).

I have a separate space for mother plant and clone.

What I mean is that, In which case, can i have the best performance for growing and flowering. a lot small spaces and a lot of less power LEDs in side by side or large spaces
for example 4x4 or 5x5 foot and use a few of powerful LEDs?

For example, a room with dimensions of 3.6 x 3.6m can be divided into 9 parts 1.2 square meters , which in this case is enough 9 powerful LEDs. Or can be divided into 36 parts 0.6 square meters, which in this case is enough 36 less power LEDs. Which is the better?

Look at “Latewood’s Favorite Video” they go thru a complete grow room build about the size you are talking about.

I can’t find it now but it was the Green Man video if anyone has the link.

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Also reflective Mylar works great, it refelects about 90-95% of the light in the room, and $25 on eBay for a descent roll you can probably wrap the entire room with 1 roll

I’d pick your light and build your space from there. I can’t give a side by side comparison, but I think it would be more efficient to consolidate into 1 space. For instance, if you have two 25W LEDs and 2 plants, I think it would allow both plants to enjoy 50W total if you made it all one space, as opposed to two, seperate chambers with 25W each.

Hi dear friend,

Please accept my apology for many questions.
I want to grow 60 of super silver haze. Can you help me in this project, please. In beginning, How much space (grow tent) and how many watts (T5) is required to 60 plants at seedling stage?


@latewood I would love for you to answer this for him, since you have experience with large grows (I think lol).

Holy cow, 60?!! That’s WAY beyond my level, I’m a beginner. For starters, to grow 60 plants to harvest at once would take a minimum room size of 8 feet by 8 feet (prefer 16’x16’) and 1500W of LED. If you’re a beginner, Is recommend starting with maybe 2-4 on the first grow!

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Thank you for your reply. I have fruit gardens in different kinds and i think that i can do it. Do I need this space and light for seedling stage?

Sorry, I’ve never started more than 6 at a time, so I’m no help on big grows. But for that many seedlings, I’d use T5 LED tubes. Just line up your seedlings (I’m assuming you’re using Solo cups or Jiffy pots?) and run lighting the length of your grow space. Something like these:



Ok, Thank you so much dear kushpa.

That is a cool video. It should be in GrowFAQs…not sure. I know you can find it on youtube. :slight_smile: