Allowance for lights

Hi, I'm new to this lark, infact only been looking into growing hydroponically for a week or so, but being an avid reader I think I've got a fair understanding of what I ought to be doing (ish).

Anyway..

I have (provisionally) decided to grow using aeroponics in a closet that is just under 8' tall.

I am planning to split the height into 2 shelves 1 for veg and 1 for flower using the SOG method. I would also have a seperate area for germination.

The square footage of the closet means I will be using 400w HPS in the flowering section and 400w MH in the veg & clone room.

Now getting to the point, I am trying to figure out if I have enough vertical space.

I believe that a 400w light should be kept about 1 foot above the top of the plant but what I don't know is how much space the light will take up to complete my calcuations. Can a HID lamp go right up to the top of the cupboard and the halo touch it (even almost) or do they need to be kept down a certain amount because of the heat if so how much should I factor in from cabinet top to underside of the light?

Any help really appreciated and any comments on what I've outlined will also be appreciated. Thanks in advance

Ern

I have 400W MH light running right now. I think you would need at least 8-10 inches of clearance above the light unless it is a cool tube to avoid a fire risk from the heat on the ceiling.

Thanks for this reply. Looks like I may struggle for space a bit here to get 2 shelves in 8 foot. I'm sort of working on veggin to 1 foot then assuming that flowering could take them up to 2 feet the aeroponics systems are around 18 inches each so its a bit tight with keeping the light a foot above the plants as well.

Any thoughts/critisisms on what I plan here more than welcome!!!!

Isn't it crazy that I can't find on any of the suppliers websites any info on how far exactly the lights should be kept from the cabinet top? I mean this is kind of essential info if your gonna build a box to fit everything and not cause a fire isn't it?

Thanks for looking guys

Ernesto said:

Any thoughts/critisisms on what I plan here more than welcome!!!!

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Gosh where to start, so many issues!

The first and most important in my opinion is, light-proofing. If you're vegging and flowering in the same closet can you make both sections light proof with no light leaks? You cannot afford ANY light leaks into your flowering room as it'll confuse and stress the plants in their 12 hours of darkness and that can cause all sorts of problems.

Second is ventilation and odour control, in that space you're going to have to run a ventilation system to change the air around the plants, (in both sections) can you do that effectively by exhausting out stale hot air out of BOTH sections and vent in fresh air via balanced air pressures?

Third is heat build up control, with two 400w systems operating in such a small space you're going to be fighting a real battle to keep temperatures down to mangeable levels.

Finally, starting with aeroponics? Is that wise? Get a soil grow under your belt its far more tolerant of mistakes - hydro and aero are not!

Personally, I think you need a rethink.

babygro said:

Gosh where to start, so many issues!

The first and most important in my opinion is, light-proofing. If you're vegging and flowering in the same closet can you make both sections light proof with no light leaks? You cannot afford ANY light leaks into your flowering room as it'll confuse and stress the plants in their 12 hours of darkness and that can cause all sorts of problems.

Second is ventilation and odour control, in that space you're going to have to run a ventilation system to change the air around the plants, (in both sections) can you do that effectively by exhausting out stale hot air out of BOTH sections and vent in fresh air via balanced air pressures?

Third is heat build up control, with two 400w systems operating in such a small space you're going to be fighting a real battle to keep temperatures down to mangeable levels.

Finally, starting with aeroponics? Is that wise? Get a soil grow under your belt its far more tolerant of mistakes - hydro and aero are not!

Personally, I think you need a rethink.

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Hi,

Thanks also for your reply

I have not attempted to explain the whole system, instead, just give an idea of what I intend to do to get the answer to the question that I raised.

I fully understand the importants of the seperate light cycles and I am sure I can totally light proof one section from the other, this should not be too difficult - If I can't I realise I would need to think again.

I intend to ventilate each seperate section and allow a seperate air intake into each section at opposite ends from the exhast fans as far away as possible from each other. I understand that there should be a full air change every 1 - 5 mins (it seems different people have different ideas on this) but I intend to provide fans that are capable of 2-3 air changes every min along with an automatic temperature sensing fan adjuster which I am hoping will be able to maintain the optimum temperature (this is kind of suck and see but if it doesn't work I will incorporate a small aircon unit), the exhast will be going where there are no odour worries.

As for starting with aeroponics, well this isn't set in stone yet but after much reading it seemed to me to be the most forward thinking way of growing around and I thought it doesn't seem to look anymore difficult than anything else other than I have read some reports of the systems failing causing the spray to stop which course will quickly kill the crop. I do realise that measurements need to be taken and levels maintained and I am aware that getting it wrong can quickly kill the crop, much more quickly than if the plants were in soil but I do much prefer the idea of soiless growing and I suppose I would have to take a jump from soil to soiless at some time anyhow so hey-ho get straight in I thought.

I thank you for your thoughts and any more are most welcome - It is great to get guidance from experienced growers.

Ern

Ernesto said:

I thank you for your thoughts and any more are most welcome - It is great to get guidance from experienced growers.

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Fair do's, you seem pretty intelligent and you seem to be thinking through all the issues fairly logically - which is a good sign. So, lets assume a few things. Lets assume you can light proof both compartments effectively, lets assume you can install and run a ventilation air exchange system for both compartments. The general rule of thumb for air exchanges is to completely change the air once every 3 minutes, so calculate your cubic capacity and multiply it by 20 (60 minutes divided by 3) this should give you your total air movement per hour, allow 30% - 50% for ducting bends and loss of efficiency - this should give you the amount of air per hour you need to flow and match it to an appropriate fan.

Lets also assume you can keep temperatures to a mangeable level (this is the one I have the biggest doubts over, MH and HPS systems kick out an awful lot of heat in such a small space - consider vegging under Envirolites, they're as good as MH systems for internode spacing) that pretty much leaves us with your original question.

For this to work and it can work in the space you've assigned, you need to focus your attention on the smaller height varieties such as Indicas or Indica/Sativa mixes forget Sativas or Sativa dominant strains they grow too tall, and think about growing them in a SCRoG system (screen of green). So reckon on vegging till 12 inches tall (plus lighting hood + 1.5-2ft distance above the plant tops) and reckon on flowering to 3-4 foot (plus lighting hood + 1.5-2ft distance above the plant tops). as plants triple in size from vegging in flowering.

As you can see, your height is very tight and is compounded by the need to keep the light a foot and a half - 2 feet above your plant tops due to the heat build up of the bulb. You can get round this a couple of ways. Firstly, you can veg under a blue Enviro, which doesn't either output as much heat as a MH would, nor need the distance, so you can have the blue enviro inches over the plant tops. Secondly, you can consider using either a cooltube on one or both of the MH and HPS bulbs (a cooltube is basically a glass cylinder that goes over the bulb and is cooled by a fan connected to one end of the glass tube and extracted out of the other side) or using a Jetstream air cooled hood, which works in exactly the same way as the cooltube, but is a conventional lighting reflector hood.

Going down either the Enviro route and/or cooltube/air cooled reflector, you can get back that height distance by allowing the bulbs much closer to the plant tops (because they're cooler) and at the same time help to sort out your high heat build up and get extra light to your plants.

It can work in that space - you may just have to throw some money at it.

Babygro, thanks for taking the time to go through this with me!

I have just realised that whilst I think oversizing my fans will cool the room suitably now (it's only about 45f outside today) it wont in the summertime when it's as hot or hotter outside than in my room.

I soon realsied that I would need to grow indica or high percentage indica hybrid and intended to use the SOG method but have read about limiting vertical growth with chicken mesh with the SCRog method and thought I may need to consider this. I had planned on vegging at around 10" and thought they would grow to about 2' when flowering. Although I am aware that they can triple in size I had read somewhere that they mainly double? and I suppose the mesh method would keep them down?

As for lights, in various guides and on forum posts it seems different people have differing ideas about light distances from plants but I have read in a number of places that a 400w should be kept up 1', a 600w 1.5' and a 1000w 2' but if I need to keep my lamps up as much as 1.5 to 2' above my plants I will definately not have the headroom for my plans.

I have brushed across enviro lights but not paid them too much attention seeing as the vast majority of advice goes with using MH and HPS but going on your recommendation and my limitations I am going to have a good read about them today. Are they as quick as MH for vegging? although if they were somewhat slower it shouldn't matter as flowering time would be slowing down the whole continuous process anyhow. What wattage would you recommend?

I have had a look at the air cooled lighting you suggested and whilst it looks an excellent solution I may have a problem with the extra venitlation needed, they seem to require a huge airflow. I was planning to duct the air out of each box and combine the ducts - I intend to calculate what a certain size of duct pipe will carry but am hoping that a 100mm pipe will be capable of carrying 240cfm (any thoughts? although I guess it will depend on bends and lengths). Anyway with the above in mind I would think that air cooled lights are out of the question without larger ducts or extra terminations.

I think my current thinking following your advice baby would have to be to look into enviro lights for vegging which save space, heat and lessen electricity costs (yeay) and look at some of the better HPS lamps which claim to be cooler and give more lumens/watt - if this does not solve my heat problem I will probably have to look at air con system.

I figure spending a bit on this lot will be worth it and will pay for itself in no time. I'm pretty sure I can build this system for less than £1000 and the cost of (not always great) weed around here is £120/oz so it wont take me long to recoup my investment, then it'll be almost free of charge, until things start to break down that is, oh and the electricity bill comes.

Ernesto said:

Babygro, thanks for taking the time to go through this with me!

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No worries Ern, I've got plenty of time and patience with people who are serious about what they want to do and have put in the time in researching the subject matter to give them a good idea of what problems they're going to come up against. I don't have much time for the people on here who piss about and can't be arsed to do any research themselves and just want people to give them all the answers - do they want people to smoke their weed for them as well?

I think going down the Indica route in either a SOG or SCRoG system is the way to go in your setup, there's plenty of good strains that are either pure Indica or Indica dominant Sativa crosses. Don't assume they will only double in size - tripling in flowering from veg growth is far more likely. The SCRoG method is essentially a technique for using a wide meshed grid for training and lst (low stress training) branches through the mesh so you create a flat canopy of leaves and branches that flower. This does not limit the height of the main cola, simply allows lower branches full access to the light. In my opinion, to grow fully matured vegged plants and clones you must allow for them to grow to approximately 3 feet in height in flowering.

The guide is for 1000 and 600 watt lamps 24-36 inches from plant tops, 400 watt, 18-24 inches. (Indoor Marijuana Horticulture - Jose Cervantes). Just because people abuse those height restrictions to get more light to the plant tops doesn't make them them correct! I say again, MH and HPS systems put out an enormous amount of heat and in the small space you're intending to use I'd be following the guidelines.

I have no experience of vegging with a MH (I veg with a blue Enviro, and so do a lot of people) and from what I understand from the practical experience of others, there's little or no difference in vegging time - some say there is and MH veges quicker, but considering the benefit you're getting from using a blue Enviro - lower heat output, lower electricity cost and tight internode spacing, even if the MH does veg quicker does it outweigh the Enviro advantages? I'd suggest not and using a blue Enviro could solve a lot of problems for you. For your area I'd suggest using 2 x 125w blue enviro's over a 200w one as you'd get more light bang for buck for not much more electricty use. A 200w blue enviro uses 123w of electricity and 2 x 125w ones 154w (2 x 77w).

The 100mm rvk fan is rated at 175m3/hour and the rvk125 125mm one 250m3/hour so that answers that question! I agree you should look at vegging under Enviro's, and strongly urge you to consider a 400w HPS cooltube hooked up to another rvk125mm - that would solve both your heat build up problems and height in one.

I don't know what you space situation is alongside the area you intend on using as your grow area, but as you're intending to spend around $1000, it might be worth considering using two rvk100's (they're under 100 bucks each) - one each to ventilate each compartment and you can control their air flow with separate fan speed controllers - the problem with using one rvk125 to ventilate both areas means even if you control it's air flow with a fan speed controller, it has to be balanced to extract the same amount of air from two different sized chambers with different heat build up issues. You won't be able to control the temperature build ups independantly of each other.

Also, regarding the HPS, take a look at the Ventronic electronic ballasts (Venture lighting) used in combination with a SunMaster (also Venture) Super Deluxe HPS bulb - that will get you the maximum amount of lumens possible from a HPS system, although I'm not sure if they do a 400w one, I know they do a 600w one.

Treat the ventilation issue seriously as in my opinion it's the most important one in your situation.

Theres some really good advice in those paragraphs there Kuddos.

Any how heres the bulbs I'd recomend if you go floresent, 105W Medium Screw (house lamp style) two to four of these will veg depending on how much power you want to use. You could also just get a smaller MH, there are a few choices compleat "Enclosed Ballast" setup or just a ballast hood/connectors and bulb (that is a 12 pack; why they did it that way I dont know?).

So anyways that hood would be good on top to; it takes a 6 inch / 152.4 mm duct =( but will at least help with heat and they have glass (good to have). If you are going to be displacing your air reguarly you could probably get away with just venting, at least the 250W, back into the veg chamber. But just changing to 150m ducting, at least up top, would be ideal.

Well I'm off to bed for now more to come.

Hey guys thanks again for the input

Well I've been all afternoon looking into these envirolites and to be honest i'm impressed by what I have found!

So if i'm right then these lights provide light within the perfect range for growing, the energy use is drastically reduced and there is very little heat going on. So if I provide the same amount of lumen using these type of lights I should (with all the theory holding tight) experience better growth than I would by using HID lamps?

I have been looking around and from what I can make of it the minimum lumen requirements for growing are 2000 Lm/sq foot but the optimum is 7000-7500 Lm. Is there any point providing more lumen than this or with this being optimum does this mean the plants could not make use of any more than this?

My growing space is likely to be around 10' square so I calculate if I were to go for optimum lumen I would go for 10 x 7500 = 75000 lumen and I can provide this by using an envirolite 6 lamp reflector with 6 x 125w bulbs. Each 125w bulb gives 12000 Lm giving me 72000 Lm, close enough!

Now I like the sound of this as using a 400w MH bulb I would only have been providing around 36000 Lm so I am doubling this, and this has got to be to benifit, hasn't it?

And the next question is, how well do these things work in the red spectrum for flowering because according to what I have read they would be at least as good as HPS provided you supplied at least the same amount of lumen but does anyone have any experience good or bad of this?

I figure they are more expensive but would save me on cooling, electricity, detection because of heat and electricity use and they would prevent any plant burn at all. The only down side I can see to this is that because they need to be kept close to the plant they need to be moved more regularly but I guess if I went away for a few days I could set it a little higher than necessary and if they got so high as to touch the bulb by return this wouldn't be a problem.

I was going to spend about £100 on each of the HPS and MH lights totalling £200 and 2 of these will cost me £400 but I will save on ventilation requirements and electricity bills and my space will have increased enough for me to grow my plants taller using more lumens meaning hopefully more yield!!!

So please if anyone has any down sides or thought on this I would love to hear about them.

-=4:20=-Guy said:

Theres some really good advice in those paragraphs there Kuddos.

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Cheers 420, don't be shy with that rep+ now

Ernesto said:

So please if anyone has any down sides or thought on this I would love to hear about them.

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Whoah ease up there Ern, don't get too carried away!

Envirolites for vegging, in my opinion are the business and a lot of people are switching over from MH to blue Envirolites because of the reasons I gave you earlier - lower operating cost, lower heat output and equally good internodal spacing if marginally slower vegging time - if any at all. The reason blue Enviro's are so successful in vegging (and the reason many people are switching over to their use over and above the reasons I've already given you) is because plants require a lot less light in vegetative growth than they do in flowering to the tune of about a 1/4. This is ideal for the lower lumen output (although 100% PAR rating) of the blue Enviro's because you can site the lamps virtually inches away from the plant tops, so all that wattage and light can be used, whereas having to have a MH light 1-2 feet away from the plant tops wastes an awful lot of light that cant be used as well as generating a lot more heat that still has to be dissipated. I'm not sure if you're familiar with the 'inverse square law' of light intensity but the further the source of light is away from it's target, the less light the tartget receives and is governed by the rule of light intensity which is Intensity = light output divided by distance squared. So a MH bulb outputting 50,000 lumens at 1 foot away will only be delivering 50,000/4 at 2 feet away = 12,500. It's not hard to see how much light is wasted with HID systems, and wasted light = wasted money.

Your minimum and optimum per sq/ft lumen requirements are a little confused I'm afraid. As I mentioned earlier, plants in vegetative growth require about 1/4 of the light they require in flowering and this is where you're getting confused. Plants require about 2,500 lumens per sq ft in vegetative growth and about 10,000 lumens per sq foot in flowering. This is why the lower lumen outputs of the blue envirolites are so good in veg and not so good in flowering. One 125w Envirolite outputs about 12,000 lumens and a 200w 18,000 (these are estimated figures) at 1 foot away on 1 sq foot of space, so 2 x 125w blue Envirolites properly spaced would produce enough light to illuminate a 10sq foot area. 12,000 x 2 = 24,000/10sq ft = 2,400 lumens per sq foot. Regarding flowering, most people agree that HPS systems are pretty hard to beat and produce harder denser buds than red Envirolites, the popular reason being due to the much higher lumen output of the HPS when compared to red Envirolites, I'm not necessarily convinced this is entirely the case and am currently researching this at the moment, but for the time being HPS is the way to go for flowering. A 400w HPS system outputting 50,000 lumens at 1 foot on 1 sq foot, would output 50,000 divided by 4 = 12,500 on 1 sq foot at 2 feet away and should be enough to illuminate a 10 sq foot area.

Also don't be fooled into thinking that because the Envirolite's don't output as much heat as the HPS or MH systems that you can get away with reducing down your ventilation requirements, you can't. Envirolites still output heat and in an enclosed space can still build up to levels that would need controlling, they won't be as bad as with MH and HPS systems but you still need to provide the plants with air exchanges that exhaust co2 depleted air with fresher co2 rich air - you still need to provide ventilation with envirolite systems.

If you choose to go down the Envirolite blue (2 x 125w) and red route (2 x 200w) using a ScroG system you'd get acceptable results, but most people feel that the (2x 125w) blue and 400w HPS system would produce better results, particularly if you fitted a cooltube to the HPS. The choice is yours really and depends entirely on whether you want to go for the higher initial outlay 2 x blue 125w 1 x 400w HPS, 2 x rvk 100 or 125's for better results and medium operating cost or the economy route of 2 x 125w blue, 2 x 200w red, 1 x 125rvk and acceptable results but lower running costs.

Damn if this isnt one of the most helpful, intelligent threads I've read here thrust far! Thanks guys for all the information shared in a thoughtful, cooperative attitude!

Baby let me start by again thanking you for the lengthy intelligent reply.

I do understand about the inverse square law and have this afternoon taken in the lack of loss of light using envirolites.

I found it hard to find figures for lumen/sq foot and really based that on one source so thanks for the heads up on that, it will certainly save some waste.

I can see where your coming from with your research re. hps systems outperforming lower lumen envirolights that are so close as to waste nothing, however my intention would be to provide the same if not more lumens than the 400w hps - if I was to try to allow 10,000 lumen/sq foot I would need 100,000 lumen for my flower box, 6 x 200w enviros would give me 108,000 or if I didn't push it that far 6 x 125w enviros would give me 72,000 lumen as opposed to the 400w hps that would only give me 50000 and thats before you take into account the inverse square law with it being 2 feet away.

I realise that I will still need to provide air changes for co2 and to expell any odour but using envirolites could I get away with using a 12v controlled pc fan in each box, some of these are very powerful these days and I have seen cheap almost silent ones that extract about 60 cfm (cubic feet/min) and 1 air change per min in each box would only require 40 cfm, I think there are more powerful ones also.

I think the main question I am posing now is that providing that the right type of light in the right part of the spectrum is used then wouldn't the light system with the higher lumen output provide the best results?

I'm haven't got around to the math yet but I think the 1200w of envirolite would be more energy efficient than 400w of hps, or maybe not I'm not sure to be fair, either way, neither way is a huge amount of electricity so its results that matter most.

I'm enjoying this thread too

OK wow that was alot more good shit but now I think we have a goal. Solving the HID or CFL choice. Right.

What would I do with as much cash as your gonna dish out on CFLs. 1000W HPS & 400W MH for up top; 2 CFLs on bottom.

I sappose you want to know my reasoning now too? OK here it goes.
(Had to add this; use rock wool and do an ebflow on top)
You have a 10sq ft blooming section witch means about 9 to 16 plants, probably 16 due to your height situation, which would be 2.6 foot worth of 8 inches each. This way you would only be focusing on main colas and not side shoots at all, as they will be side by side and about 1-1/2 feet tall in the end.

Onto the bottom for a second; if your room can only support 16 plants max then your veg/starting room floor space dosnt need to be as large as the top. Say 4 inches each and you would need half the space. This does two things for you, it will give you some extra space for your resivors, and lower your lighting requrirements. With both your resivors on bottom you will gain some more head room up top.

OK now back up top; and heres my thinking behind the 400W MH. You get them started under the CFLs, 2 weeks or so, in starter rockwool cubes. Leave two of them in the bottom under the CFLs, to take your next clones from, and put them all in 8 inch rockwool. Move the rest up top to the 400W MH for about 2 weeks. Switch your lights and thats about that. This way will add 2 weeks to the normal cycle since the budding room would be needed to finish up the Veg stage, but will require minimal Clone/Seedling levels of light and cooling below.

All that being said, the 400W MH may be a bit much. Kinda like all those CFLs. The good part about this way is that they would be getting increasing levels of light at each stage, it accomidates motheres, all the major heat would be in one section instaid of both, and it would stay in the price range of 400 euros. I did the pricing here and it includes the GOOD bulbs which are more costly.

Well just another option for you to concider, and its all tried and true equipment.

Ernesto said:

Baby let me start by again thanking you for the lengthy intelligent reply.

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No worries Ern, I know how useful it is to talk through these issues and get your head round which ones are important and which ones aren't.

Again, I think your figures are slightly out because you're not taking into consideration a few factors. Firstly, the rating for lumen outputs for all bulbs (as far as I'm aware anyway) is given at 1 foot away falling on 1 square foot of space. We don't use Envirolites at 1 foot away do we? We use them virtually inches off the plant tops, so using the inverse square law in reverse, we need to quarter the amount of light given at 1 foot distance. In reality it will be slightly more than a quarter due to the couple of inches. So, to illuminate 10 sq feet with approximately 10,000 lumens of light per square foot, with the bulb at 1 foot away wed need as you said 100,000 lumens. To illuminate 10 square feet with the bulb inches off the plant tops we quarter the 100,000 lumens = 25,000 lumen outout. This suggests that 2 x 125w Enviro's would be sufficient (2 x 12,000) but I would probably use either 3 x 125w Enviro's (to compensate for those couple of inches off the plant tops) which is convenient because in 10 sq feet (assuming the dimensions are something like 4 x 2.5 feet) you'd probably only get 3 Envirolites in that space, or 2 x 200w Enviro's. You can see now why with Envirolites it's important to use a SCRoG system, because of the closeness of the plant tops to the light and that the light doesn't penetrate far down, or diminishes rapidly as it goes down.

The alternative is to use a HPS system and this is what most people do and report very good results with it. As I mentioned earlier I'm still researching why HPS systems produce better results than Envirolites and it may be due to a number of factors, total light output only being one of them, but people are in general agreement that HPS systems produce harder, denser, fatter buds than Envirolites do. If you're not fussed about absolute perfection and only want useable results at a reasonable running cost, Enviro's are the way to go, if you want the very best results you can at a higher running cost HPS is the way to go. To get the 10,000 lumens with a HPS system you'd probably have to use a 600w system with a cooltube. 600w HPS systems produce the most lumens per watt of any of the various wattage bulbs and should output about 90,000 lumens at 1 foot on 1 sq foot of space. You can easily place a 600w HPS with a cooltube at 1 foot away from the plant tops and that would give you 9,000 lumens per square foot.

Regarding ventilation and heat and odour control as far as I'm concerned PC fans and 60cfm isn't enough. Envirolites still output a lot of heat and in the small space you're talking about that heat will build up and needs to be exhausted and vented efficently. Ventilation strangely seems one of the areas where people try to skimp and save and its the one area they shouldn't as it's quite critical to the health of plants that they receive not only a constant supply of fresh co2 rich air to continue their healthy growth but that the hot stale co2 exhausted air is vented out. As I mentioned in another post in your small space with the amount of lights you're intending on using you're going to have real heat issues and a 60cfm fan simply isn't going to cut it in either exhausting air effectively or keeping temperatures under control. If for no other reason, just take my word for it.

Thanks guys

420, The set up you suggest sounds very good and the costs are lower than I am looking at right now but before I can go back to considering HID lamps I just want to get my head straight on env lites for both sections and when I put that to bed I can start to consider HID lamps again and how best to go about that, so I have just a couple more question for Baby, (though the trouble with questions is that they seem to lead to questions!)

To start with, just say theoretically, what happens if I start to use more than 10,000 lumens/foot? I have read that there is no amount of light that the plants can't use but I take the optimum to be 10,000 lumens (the same roughly as the sun???) - so how quickly does the usefulness of extra light taper off, is there a scale for this? If I was to provide 20,000 lumens/foot would I see a good increase in quantity or quality of bud or would they just grow a little bigger or a little faster or do growers sum up that the extra lighting cost is not worth the extra gains? (though with lower running costs of envlites would this still hold true?)

The dimensions of the room you guessed are just about right but I can fit more envlites than you say, take a look at this unit 200w x 6 MG Envirolite Grow Light: Basement Lighting Hydroponics and Plant Grow Lights unless they have got the sizing wrong this hood is just under 4 foot by 2 foot and holds 6 200w envlites - it ain't cheap mind.

I have seen looking about at many postings on many forums that most agree HPS gives better buds although none I have seen seem to offer an explaination for this, I will be interested in what you find out.

Regarding ventilation - whenever you read about envlites they harp on about how cool they burn so it is easy to get carried away with the idea of hardly any heat - is the heat build up really significant? If each room is 40 cubic feet then a 40 cfm fan would provide an air change every min which is more than enough to provide for the co2 requirements of the plants (in my case it would be going straight up very little distance with no bends) so how much extra would you suggest I need for sufficient odour and heat exahust and what ever you deem this to be, if I could purchase a pc fan that moved this amount of air would that not be sufficient? after all is a fan capable of moving 100 cfm not a fan capable of moving 100 cfm? longevity may be an issue but then again many pc's are run 24 hours a day although I don't suppose that the fan is flat out all the time. Are there other issues I need to take into account?

As I say, thanks for taking the time to read through this again, I do really appreciate this - I want to get it right before I go and spend out, I think while I am still mulling over all of this I am going to try and knock up a couple of those diy aeroponics boxes in the diy section on this site - they look pretty straight forward to make and will save me money I can spend on light and vent. Or do I start another thread 'should I use aeroponics' and then go around in circles with that one for a bit

Plants can only process and photosynthesise so much light, beyond that it becomes diminishing returns. I've given you the two optimum levels of light for both stages of growth - Vegetative 2,500 lumens per sq foot and flowering 10,000 lumens per square foot - if you give them more than this then it's wasted money. There's little or no evidence that suggests that giving plants more than 18 hours in vegetative growth speeds up their growth or any more or less than 12/12 in flowering growth has any affect on bud and flowering formation. Many people get away with less quantities than the optimums I've given you and still produce very acceptable results.

Fair enough on the 6 Enviro's, I'd allowed for more space around the bulbs and had them lengthways on the 2 foot dimension, rather than end to end, but if a 6 Enviro hood exists and it is those dimensions (and the dimensions do look right, they're about 17 inches long with holder and 9 inches wide at the widest point) then oyu have a ready made solution, but beleive me, those 6 Enviro's are going to kick out some serious heat! And yes, the heat is significant, paticularly in a confined space. To give you an idea of what you're up against, I'm currently vegging 3 plants under a 1 x 200w blue Enviro in a space size of 1.8m high, .76m wide and .6m deep with a rvk 100 running at 3/4 speed extracting through a 100mm hole in the top of the chamber and a 120sq cm passive vent at the bottom of the chamber and I'm struggling to keep the temperatures in there under 28 degrees c ! It's fair to say my ventilation setup isn't ideal and I'm not running any circulation fans in there at the moment (which do help) and simply relying on the passive vent for fresh air circulation and it is in one of the warmer areas of the flat, but even still, you can see what you're up against and 6 125w Enviro's in the small areas you''re talking about are going to need some serious cfm ventilation power to keep temperatures under control, and PC fans simply are not up to the task.

I also think, as I said earlier, you need to think quite carefully about aeroponics, you can get some rapid results with it, you can also get some dead plants very quickly if any of your pumps fail for any reason!

Its very good to explore all of your options before diving in. That is why you have recived so much help here. I see posts all the time about how some guy has new plants growing under incadesent or halogen bulbs and wants to know what nutriants he should buy. You probably allready know whats wrong with that picture and you havent even started your plants yet.

So anyways on to the lighting stuff. There is still 1 factor that is yet to be referanced and I feel I should point out. Reflectors are the reason that your numbers are off. Only 1/3 of your light is facing down, lumens readings are only accounting for output of the bulb and dosnt include the other 2/3, of the lights circumferance, your reflector redirects back down at 95% efficancy.

With all respect I have had a further read on plant and photosynthesys to confim what I had already read, but as I understand it plants cannot get too much light but can get too much heat, photosynthesys and other plant growth processes will shut down when the environmental and tissue temperatures get so high that all of the water taken up by the plant is used to cool the plant tissue.

With this in mind, do you think there is a fair possibility that by using cooler lights and by keeping the environment at the right temperature that further light could produce more plant growth as the tissue temperatures would not be raised so much and more of the water can be used for growth than for cooling? And with energy cost being less with cfl's couldn't that also move the optimum amount of light provided out as creating extra light costs less?

I take your point on ventilation and I want to get this right first time if I can so what I think I will try to do is, when I have worked out what light I think I ought to use, calculate the heat generated in my rooms and size the fans and ducting as perfectly as possible to dissapate the heat produced by lighting and equipment, but this get impossible when temperatures outside are the same or higher than in your grow room doesn't it? Any help here appreciated!

As for the aeroponics, in all fairness I have only watched a few vids, read one or 2 guides and haven't really had a read around the forums on this, I have just accepted it to be the best modern method which is gaining momentum amongst growers. I will have a read about today and see what experiences users are having with it. I know what your saying about the pump failing and the sudden plant death that can occur but I do have a plan to combat that, I intend to make some adjustments to the diy aeroponic plans - I cannot in any case get a box that is big enough to fit my grow room in full and to make it smaller is a waste of grow space so I intend to use 2 boxes side by side, originally I was going to use one large pump in one box and link it to the other but I am now thinking of putting a smaller pump into each box and linking the systems and should one fail then the plants will have the security of the second pump, albeit the spray rate will be limited but hopefully it would give me enough time to sort any problems out.