does glass reduce lumen's by 30%?

[greenduck]

hey there, im trying to find information on how much the lumen's or pars are reduced when the hoods have glass on them. is it around 30% for all hood glass or does that vary among the product like how different bulb manufacturers have different mean lumen average ratings.

also, i see some hps bulbs have different mean lumen averages but its not really based on price. for instance. ive seen some cheaper bulbs with a better mean lumen average output then an expensive bulb.

please fill me in with some knowledge. i get that pars are based on the distance from the bulb emission and lumens is the average output,correct?

so how should i deduce from all this knowledge what to focus on when making my next bulb hood purchase for my flowering tables. Ballast dependent of course. but lets say for my 600watt digital ballast.

cheers.

 

[supermanlives]

i didnt think it was that high a loss. but have no way to test. interested to hear what peeps say. i always thought it was less than that

 

[greenduck]

https://www.icmag.com/ic/showthread.php?t=51325&page=3

this is the link to a thread on PAR scoring with different hoods, different heights, and in the first couple pages i saw this " If we just estimate 2-3% loss with glass we can say that it would have probably been 2550 average with glass on"

does this go with lumens? not really sure. my buddy keeps saying it cuts the like by 30%, maybe its less but he thinks he knows it all so, we'll findout...hopefully! lol

 

[greenduck]

?

 

[messn'n'gommin']

Material used to make the pane and its thickness is relevant. But, without a light meter, it's a fair guess to say you lose about 10%.

hth

 

[Dislexus]

How is this offset by being able to get your lights closer to the plants if you air-cool.

 

[Yes4Prop215]

ive grown the same exact strain under the same exact hood with glass on and off and didnt notice a single difference at all in cola size, trichome coverage, or final quality.....

if anything the hood without the glass fried some of the nugs because of all the heat coming off it...


im sure a few lumens are lost but the plants dont seem to mind....this also goes along with the argument that some people say you gotta slam your hoods on the plant, although i have been in other gardens were the growers raise the lights 2-3 feet high and still produces really good nugs....and the 1st place cup winner at the IC cup said he had his hoods raised pretty high too...


ENVIRONMENT OVER LUMENS i remember hearing that advice back in the day and it stuck with me.....now i raise my hoods over 2+ feet if theres no glass...with glass around 16 inches-2 feet...i prefer using glass because i like aircooling the hoods helps regulate temps...

 

[whazzup]

30% is a bit much... I would say, depending on the glass quality, average around 8-10%.

Light is just one of the factors that define your yield. Every grow is different, even the different seasons have effect on your grow. I agree that climate has a great influence on your crop and yield. Also, adding more light does not necessary generate equally more yield when you are at the top of what is efficient for your plant. When everything is perfect then more light can give you more yield, provided that you are not at the max of your plant yet.

Without a glass shield you grow a bit different, using overlapping lights on a bit bigger distance, creating a better penetration of the crop.

oh, and lumens don't really say a lot. It's the photons you need to count. Remember that you lose almost all UVB radiation with a glass shield and most MH are not suitable for an open fixture.

 

[headband 707]

OH YES you can get a light meter to measure your light and see what is getting through.. They now make windows to either let the UV through or not lol. Anyways yes this has always been an issue in greenhouses ect. So depending on your glass will obviously depend on how much will get through. peace out Headband707

 

[greenduck]

wow guys, thanks for the knowledge and experience. its good to know that the glass (depending on the quality as noted above) doesnt really seem to change the quality of yeild. ill test it out and let you guys know in the future. peace!

 

[whazzup]

I think that is a wrong conclusion. First, you lose light (so efficiency goes down by about 10%) secondly with most glass you lose UVB spectrum (when using MH that actually have UVB). The latter won't cost you a lot of yield, but it does make a quality difference.

What I haven't even counted yet is that many lamps, when actively cooled, have a lower output.

So, in any case you lose light and efficiency. In some cases you lose quality.

 

[Dislexus]

Holy shit I just found a great air-cooled reflector...

See the main problem with air-cooling is maybe you need to clean that glass/alumabrite in between harvests eh? If you don't I could believe 20% loss of light.

Well with cooltubes you gotta remove the tape and one of the ducts to get in there.

With glass-bottomed reflectors you have to tape up the edge of the glass so you dont have any odor sucked into your non-scrubbed high velocity ventillation for the air-cooling.

I just found that theres a better reflector out there!

Check out the C.A.P. Lumenaire 6... the bottom edge of the reflector that holds the glass has no seams, it has a clasp making it oh so easily removeable-and-cleanable, and I *imagine* theres a gasket in there completely sealing it up. Awesome.

 

[CFP65]

well i would say that try and find lead free glass, ie the kind used in solarpanels, the thinnest kind you can get hold of.

 

[growshopfrank]

How is this offset by being able to get your lights closer to the plants if you air-cool.

when you get real close issues like bleaching and reduced footprint tend to rear their ugly head glass or no glass

FWIW link for duponts UV passing glass
http://www2.dupont.com/SafetyGlass/en_US/whats_new/worlds_first_uvbreathable_glass.html

 

[MrShpongle]

So yesterday I remembered that it had been months since I had last cleaned the glass in my veg room, and remembering this thread I decided to take measurements with my light meter. The results surprised me.

No glass: 118
Clean glass: 114 (3.3% loss)
Dirty glass: 112 (5.0% loss)

So I don't know where ya'll are getting these 20-30% numbers from. This was measured in lumens, not PAR, but I doubt it makes a difference. As for the reduction in UVB that's a different story - and one which I can't make any conclusions on.

 

[CFP65]

@MrShpongle

could you try to measure, the lumens when you place reflector as low as you can get it with the glass on without burning the plants, and second could you try measure without glass at the normal application distance.
ie. if you have glass on you could maby have the lamp 8inces over the tops
and if you take the glass off you would maby be forced to increase the distance to 15-20 inces.
it would be wery interestimng to see the lumens difference for real use application.

 

[greenduck]

@MrShpongle - what were you using to measure the lumens?

I have two rooms so the first 4 weeks of flower i have hoods with glass. the other room has the a/c, co2, and NO glass so uvb is getting unobstructed.

are you guys really cleaning the glass on the hood??? inside and out? what do you clean with.

has anyone place a higher wattage bulb in their hood. example, I just placed 1000w bulbs in my 750 watt hps hoods. (750watt ballast) does this increase the lumens a little?

 

[satyr]

Your bulb will not be operating within its optimal temperature/input range, and therefore likely not perform optimum, making it a bad idea.

I like to use the Adjustawing because of its cooling properties, it functions like a big radiator. Not counting the footprint and flexibility.

I can easily go down on 25-30 centimeter with a 600 watt without burning the tops, as long as I have a cool stream of air right above the reflector. Aircooled hoods and tubes stuff are waste and more work unless you run Co2. You get a shitty footprint, and even if you have a reflector mounted on the tube you loose even more lumens when light go through the glass before hitting the reflector. Then the issue with hot-spots, most people underestimating how much air is needed to push through the tube to get the heat away, loosing lots of airpressure cause the pipes are bending and knotting making lots of heat just beneath the bulb...on and on

I just get don't people without Co2 using aircooled tube with or without reflectors, if you learn to handle a reflector with good heat distributing abilities you have given yourself an advantage and can go almost as low, but with a superior footprint. Don't forget the importance of environment and proper aircirculation, this is not helped with a cooltube either.

 

[Yes4Prop215]

satyr i have heard different from some friends who say that when you are running co2 to run open bulb no glass and raise them up a bit because you want the temps to be a little higher......i dont currently use co2 but i use AC hoods to help keep my temps down got a 6in blowing through 2 hoods, i run intake/exhaust so no airconditioner just a dehuey and gambling on not having heat waves....for sealed rooms with co2 i was told that its not good to go with aircooled lights because it can create possible co2 leaks that will drain your tanks quickly, unless you were able to place the fan outside the growroom and run ducting into and out of it perfectly....i was wondering that exact thing because im tired of I/E i want to go sealed co2 and have been consulting a few of my friends about it and thats what they tell me...not trying to start an argument i would love to be proven wrong but want to know why...i wanted to keep doing AC to keep some of the heat out of the sealed room, but was told by different growers that its better to run open bulb..

also i think cooltubes help the environment because all that heat is being sucked out and not thrown onto the plants....environment and air circulation is the most important part, and with AC tubes/hoods it helps air circulation because theres less hot air that needs to be dispersed in the room...


i honestly just dont think the distance or lumens really matter but im still testing things out....i slam the lights during veg and early flower...but ive been raising them up a good 2 feet from the canopy and still getting the same tric developement nice caked sparkly stuff......next run im gonna pull the lights up to like 2.5-3 feet and see what happens who knows maybe quality will slack...but i was just in my friends grow who had his lights very high up maybe 3 feet at least and his nugs were almost picture perfect nice frost just very healthy looking plants.....also in greenhouses the plants still produce really nice buds even with that white canopy filtering out alot of the sun....UV burn and heat stress are worse to quality in my opinion...open to different thoughts..

 

[moses wellfleet]

very interesting thread... Green Duck what is your reason for using air cooled hoods and what are you using at the moment? i have used both adjust a wings and octagonal hoods with a light mover. the adjust a wings are excellent for dispersing heat because of the open ended design they run way cooler than my octagonal reflectors. if reducing heat is your primary objective i think it wise to try an open ended reflector first... i too want to try air cooled hoods but i am hesitant because of the labour intensive upkeep of them imagine you break the glass while cleaning them?... i have found during my 8 years of growing that i often try to solve a problem with hi tec solutions and end up creating more problems in the process!

with regards to the level you hang your lights i think this obsession with having the lights as close as possible to increase lumens is misguided. i had my best yields and quality buds with the adjust a wing 400w about 2ft above the canopy... i thought hot dam if i lower the lights it can only get better, the yield actually decreased when i lowered the lights!