i already have a 400w hps .. puts off alot of heat (due to having the ballast integrated into the unit) . the closet is 4 feet wide .. 2 feet deep and 7 feet tall. im expanding the closet as much as i can the new closet will be 4 feet wide, 4 feet deep, 7 feet tall. im looking to add some light, without heat .. so CFL's are the way to go. at the moment, the 400w HPS is being used from seed to harvest. when buying the CFLS, should i go all 2700? all 6500? or a mixture of both ?
If you are going to use the CFLs in combination with the HPS I'd say go with daylight bulbs at 6500k. That way you can have both spectrums as the HPS is mostly red. But how many plants are you growing. And are u in veg or flowering? And why do you want to add more light?
well u got ur bloom spectrum covered so why not supplement with veg spectrum. do you have a switchable ballast? damn soul you stole my thoughts!
Have to agree with the above, go with 5500-6500k daylight bulbs. You already have plenty of red/orange so get some blue on there. Also I saw on here awhile back some charts that show chlorophyl efficiency at different color temps. Blue light enables the most efficient chlorophyl reactions, but red spectrum is necessary to trigger bud production. Also saw where someone did a side-by-side comparison, growing under CFLs. They took two clones both vegged under blue CFLs then one went to flower under all reds, the other stayed under blue. The blue light plant yielded slightly more even in the absence of any red spectrum to tell it to bud. So I've deduced that plants look at light duration and light color to determine when to flower. Under the natural sun the dawn and dusk are more red/ midday is mostly blue light. As the days get shorter there is more abundant red spectrum light so the plants tend to use it more (even if the blue spectrum reaction is more efficient). Therefore, under our artificial conditions, we may can benefit from minimal red spectrum in the flowering phase, allowing mostly blue spectrum and it's super-efficient reaction processes to maximize yield. I'm trying this in my current grow, I used 1/4 blue 3/4 red for flowering in the past, but for this grow I'm gonna go 1/2 and 1/2 and the next set of clones will go 2/3 blue to 1/3 red. All clones will be from the same mother so I'll be able to tell which combination works the best.
I would recommend all red spectrum for flowering, and a mix for veg/preflower. Once the internodes have started reducing to bud size, go all red. People I have read results from get worse flower results mixing spectrums generally. I imagine the blue light's ability to shorten internodes has some negative effect on flowering. I'm also pretty sure this is why LED grows outperform in veg and underperform in flower. Also, instead of CFLs, I would recommend T5s. You can get pure blue/red T5s from philips and a few other companies, and the bulbs don't have a ballast so it's cheaper in the long run than CFLs. Get two 4'x4tube fixtures, hang one above the plants and one across the side. You will suck 432W, and outperform your 400W HPS by leaps and bounds while not needing cooling save for a standard fan. Using standard 6500k/3000k T5s will work, but I strongly recommend the red/blue bulbs.