Things you might want to know

The main thing that I have found in indoor gardening is to get your environment right!!!  Easier said than done, eh?  Not really.  Having or finding the right information is the key to gardening success!  

 

Knowledge is a gift to those who do not have it.  

 

Did you know that in tents and small grow areas that just by placing the ballast outside the grow area will reduce the need for 3000 - 5000 BTU's of cooling power?

 

Lumens per square foot:

Minimum amount of lighting needed is around 2000 lumens per square foot.
Mid range is around 5000 lumens per square foot.
Optimal is 7000-7500, or higher, lumens per square foot.

Watts per square foot (wattage per sq ft WILL vary by light source):

Minimum wattage per sq ft.: 30w
Mid Range wattage per sq ft.: 50w
Optimal Range wattage per sq ft.: 50-80w

To most accurately ascertain the proper amount of lighting needed for your space, there are several things that you have to know. At this point, a couple of definitions are in order.

Lumens - one lumen is equal to the amount of light emitted by one candle that falls on one square foot of surface one foot away.
Watts – A measure of the amount of electricity flowing through a wire. Watt hours measure the amount of watts used in one hour. A kilowatt/hour (KWH) is 1000 watt/hours.
Light Spectrum – In simplest terms – Blue (425nm – 460nm, think a 6500k CFL or MH) & Red (630 – 660nm 2700k CFL or HPS). Blue wavelengths are associated with vegetative growth, and reds with rooting & blooming.

 

To determine how many lumens per square foot you have:

Find out the square footage of your space.
Width x Depth = Square feet. Divide the lumens available by your square footage.
This will give you lumens per square foot.

Example: Say your space is 3 feet deep by 4 feet wide, 12 square feet. The total lumens available from your light(s) is 45000 lumens. 45000/12 = 3750 lumens per square foot.

What if you want to determine how much light you need in watts?
The general rule of thumb for providing light for an area is a minimum of 30 watts per square foot. 50+ watts per square foot is optimal. You can determine the proper lighting for your area by using this formula:

50 watts (or the total watts you are using) x (your square footage). Example: You have an area of 10 sq. ft. – 50w x 10 s.f. = 500watts/sq.ft minimum or 50 watts x 10 s.f. = 500 watts/sq. ft. (optimal). Also, remember that fluorescent's are weaker and emit less light than an HID. This means you will need 5 times the amount of wattage to equal the output of an HID. So, 30 watts of HID would equal 150 watts of fluorescent's. This is why it is advised to provide a minimum of 30 watts per square foot for HID lights and aminimum of 150 watts per square foot for fluorescent's.

In more detail - How much light do I need?

Chlorophyll & photosynthesis both peak at both ends of the visible light spectrum

Technology has advanced so much in the last 15 years that we are constantly refining the process and updating what we know works best for growing. Current theory holds that the Minimum amount of lighting needed to sustain growth is around 2000 lumens per square foot. Mid range is around 5000 lumens per square foot. Optimal is 7000-7500, or higher, lumens per square foot.

What if you want to determine how much light you need in watts? The general rule of thumb for providing light for an area is a minimum of 30 watts per square foot. 50 watts per square foot is optimal. You can determine the proper lighting for your area by using this formula: 30 watts (or 50) x ?(your) square feet. Example: You have an area of 10 sq. ft. – 30w x 10 s.f. = 300watts/sq.ft minimum or 50 watts x 10 s.f. = 500 watts/sq. ft. (optimal). Also, remember that fluorescent's are weaker and emit less light than an HID. This means you will need 5 times the amount of wattage to equal the output of an HID. So, 30 watts of HID would equal 150 watts of fluorescent's. This is why it is advised to provide a minimum of 30 watts per square foot for HID lights and a minimum of 150 watts per square foot for fluorescent's.

Theoritical Light Spectrum for indoor cannabis (Though LEDs are left out, they occupy a more efficient spectra than most HIDs)

This is all important because the light intensity will directly affect the quality and yield of your crop. If you have less than optimal lighting your yield and potency will be reduced and buds will not develop as dense. This point can not be stressed enough. You must have the right amount of light for your space to grow high quality bud. The question is often asked, “can I have too MUCH light?“. Theoretically, yes you can, but in practicality you probably won't. According to the law of diminishing returns, you could theoretically reach a point when your plants just couldn't absorb any more light but it would be impractical and inefficient to do so. Heat from the lights would become a problem long before you ever reached that point. So use as many lights as you want, just control the heat.

Experimentation is the only sure method to determine the best solution for each plant. If plants are not receiving enough light, they begin to grow tall and spindly as if stretching for the light and foliage becomes pale green. Or, if they need to be moved closer to the light, or given a longer light exposure period. Too much light may lead to bleaching of leaves and flowers, browning and shriveling. Leaves would become overly compact and curl under at the edges.

 

In a correct ventilation setup, proper air exchange is only achieved by having a supply and return to the space needing ventilated.