I think the guys here though have got the measurements wrong. I believe that the 68" is the height and the 38 x 24 are the sq ft dimensions. Dimensions are usually stated as length x width x height, so it can be confusing when the height is listed first. So, I believe that we are looking at 6.33 sq ft (38" x 24")...is this correct as this makes a huge difference in everything. And since I do not believe that you have a tent that is either 38 or 24" high, I am going to use the 6.33 sq ft for figuring lighting for you.
So, I am going with those dimensions. Unfortunately, you are going to generate heat unless you have around $500 or so to spend just on LED lighting. LEDs have come down a lot in price, but they are still expensive and there is still a lot of lying by the manufacturers and salespeople as to how much area they will cover. When I was looking at LEDs, I was told (by someone who uses and knows LEDs) that I would need about 600W for a 7 sq ft tent.
While you can grow with CFLs, when you get as many as you need, they will generate more heat than HPS lighting, produce substantially less, cost more to run, and probably be more to purchase initially. Let's look at 42W CFLs as they are common and readily available. We use actual wattage when speaking of CFLs as the equivalent wattage is a useless figure and means nothing to plants. These put out about 2600-2700 lumens. A space of 6.33 sq ft is going to require 31,650 lumens for minimal lighting. If using 42W CFL, you would need 12 42W CFLs to get to minimal lighting. Add to this the cost of cords, sockets, and reflectors and you are in more money than a 400W HPS/MH. The bulbs alone run about $10 each. Then there is the added electrical cost each and every month--over 500W for 32,400 lumens.
Next let's look at fluorescent tube lighting. While the T12 and the T8s have pretty much the same problems as the CFLs (too few lumens per watt and no penetration), T5 tube lighting is different. It puts out about 50-60% more light per watt than other tube lighting. It is about the same or a little better than MH at 92-100 lumens per watt. T5s are my preferred lighting for vegging. I recently purchased a 2' 12 tube T5 (288W) that puts out 30,000 lumens and have been very happy with it. Something like that would leave you slightly underlit, but it would probably be your best, cheapest option. And while it is far better than CFLs, it is still a long ways away from what a HPS can do for you.
HPS is my favorite for flowering and the choice of many others. I personally find that I need the heat of the light during the winter or my space can get too cold. For a space that size, a 400W with a digital ballast would be your best choice. There are packages that come with the dimmable ballast, hangers, a cool tube reflector, timer, and both HPS and MH bulbs. You can pick up a 400W HPS/MH combo for around $150-170 on Amazon.
You are going to need ventilation regardless of what light source you choose. Ventilation is for more than heat control. Plants need a continual supply of fresh air all the time the lights are on for proper photosynthesis. This is accomplished with the use of a centrifuge type exhaust fan. You also need an oscillating fan of some kind to move the air around.
I always try to let new growers know that this is not like growing veggies--there IS a reason that it is expensive. Cannabis is finicky and it has certain wants and needs that must be met. And it is not cheap to set up a proper grow. Scrimping on light is about the worst thing you can do, but there are plenty of other things to trip you up along the way. This is also a long process taking about 4 months start to finish. And you can get 3-1/2 months in and have something happen that ruins your entire crop.
So, let us know what your budget is and we will try and give you the best advise we can to get your properly lit and set up.
enjoy the ride
