Lol I measure my temps in several places but around the roots or pits is my main number i use
Since thus will tell tou your root temps more accurately
I do also read at canopy level to ensure heat isnt a issue ill do a daily check wuth my hand as well @Lucky
As @Donaldj stated i am a commercial hvac guy so i can help with any issues you have in this area
Donald is also knowledgeable in this area as well
And has some good outside the box ideas
I run ac in summer so grow room temp maintain around the same numbers I maintain a 68 in summer
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I think @dbrn32 said it best it is all a numbers game with every possible edge or % being a plus so when I spent 400 on my bulb and ballast I read everything I could about them looking for an extra % here and there. Let’s be honest we are all here to try and add a few more grams to our yields and any loss in efficiency is counter productive and if someone offers a suggestion which can improve my efficiency by 2-5% I am all for trying it
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Do you have any scientific studies to support that premise? In cinema putting a clear sheet of glass in front of a light doesn’t reduce it’s strength either.
How are you measuring strength? I’ll have to look at what’s out there for scientific studies. My comments are based on measurement, although due to the crude nature of said measuring anything I’ve done would be very difficult to consider scientific.
I would think the basic concept would be pretty easy to grasp though. A piece of glass in front of a light gets hot, is transforming some of that light energy into heat. I guess I’ve never thought about it beyond that. I would guess that in cinema there’s probably a higher standard in optic quality, which would probably reduce any losses. But I wouldn’t be convinced there’s none.
Playing devils advocate here simply because I’m not above learning… Are there any scientific studies that prove that 100% of light energy is transmitted through glass?
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You can very easily take a light/lux meter, secure it in a fixed place with your light source shining directly upon meter - take a reading. Then put a sheet of glass between the two, take another reading.
Now, maybe there is something I’m not aware in PAR wavelengths which is somehow affected by glass, IDK. Regular light strength I don’t think so. BTW - the closer the (clear) glass to the bulb (say mounted in a hood), probably the less influence.
Can’t comment one way or the other on distance. One of the bigger problems with lux meters for our application is that they measure in photometric units rather than radiometric units. That’s my understanding anyway. So we’re talking how bright does this light appear vs how much energy does this light produce. Correct? So there’s no need to go down the path of whether plants care what a light source looks like.
Uv wavelengths are outside of the par range, specifically uvb which is what we’d be talking about with Cmh and to my understanding have the hardest time passing through glass. Out of the wavelengths we’d typically be concerned about anyway.
I have a few things to do tonight, but I’ll check on those scientific studies.
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Still shy on scientific studies. I certainly can’t find anything at all supporting glass has no effect on light.
I did find this…
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Like I said, UV will bleach art behind glass - including “UV resistant glass”. A number of tests online showing this happen.
lux or lummes arent effected by the glass
But your par valves would be par reads more of the light waves not seen by the human eye 
unlike lummes which is a reading of light we can see
Hes not saying it blocks 100% of the uv either @Lucky @dbrn32 is saying you have a drop in the number under glass so your right art will be exposed to uv under glass
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Not going to argue but a PAR reading with glass and 1 without is easy 5% all cooled shades for CMH cool the shade and not the bulb just simple facts run standard MH?HPS vented shade at your own risk at over 100 a bulb for good bulbs I stick to what works for me and what designers suggest my biggest risk is no glass if a bulb does blow pop
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I’ll take your word for it on the art. I’m not an artist, photographer, or collector of either. We’re talking about the effects glass has on grow lights.
We’re just trying to help you out, you’re free to take our advice or leave it as you see fit.
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Ok, if I may chime in @dbrn32 @Countryboyjvd1971 @peachfuzz @Donaldj,
@Lucky it’s true that behind glass some damage can be done by some UV’s , in fact it’s the UVA’s that do it, not UVB’s and if an art gallery is stupid enough to let art in sunlight or daylight, sorry, but they should be out of business…
Glass will stop 100 % of the UVB’s and UVC’s , even if expose to direct sunlight.
UVA’s in the other hand are at a shorter wavelengths, and that’s partialy why art galery and cinématographique art are avoïding UV’s except for certain form of art (UV’s art for exemple)
Aaah, I praticly ear you saying, what scientific background or studies I have in that domain… Eeeeh!!! Just to mention, I am diplomee in printing and visual art, with a certificate from Nikon institute in light and lenses. I also have scientific studies in other domains that’s not related to the subject or maybe a little…
So, I do believe that my friends gave you great answers and obviously you mix up between photometric units and radiometric units mesurement… Even if lux and lumens are important, when come the time to mesure the full spectrum , radiometric units instruments measurement is the way to go… And your lux meter will never gone a give you indepedent UV’S measure… 
So, UVB’S are desirable when come to growing (did I say that I have study in that field too, 
)
It will help in the fight against pests and mold , but also help in the developement of the plant in multiple ways like the developement and maturation of trichomes, the goodness, is coming from there, essentialy…
So, if you want to leave or put a glass in your CMH, fine, however, you essentialy cut some of the reason why investing in that kind of light for horticulture purpose…
I hope that’s gone a help you, Lucky, I wish you a Happy growing…
~Al 
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Do you have any studies to support your beliefs and assertions?
As a far as UV glass, it’s pretty commonly sold and used all over by framers (not just display galleries - which often aren’t well lit by daylight anyway), but it’s a fallacy that it will protect against loss of fugitive pigments. Some galleries know this, maybe some don’t.
As far as the rest, it probably is more a question of degree than yes/no, all/nothing.
If there is a large difference between PAR and lux degrees behind glass (or not) it would be really easy to test - maybe there are some videos online, IDK. I don’t own a PAR meter, almost everyone has access to a light meter today.
Everyone seems to have notions and urban myths, I’m looking for hard science.
I just scanned aquarium/reef forums, the consensus there seems to be there is very little affect (if any) on PAR - when there is a difference, it is often the glass needs cleaning. I’ll contact a bulb manufacturer for the truth.
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In fact I do and I already mention it.
Here’s a simple graph that is really easy to understand, however it’s scientificly hard rooted…
Today, for toughness and safeness, glasses are made of polycarbonate or plastic…
If you want, you can choose to go with regular 4mm glass (silicate) but only around 25% of the UVB’s are gone a pass through and gone a be diluted when reaching the canopy. The intensity of light decreases as the inverse square of the distance from the source.
It’s at your own risk because it is more fragile but you will be able to have a vented hood if you wish… This is valid for non-UV treated and ordinary glasses…
Their are some risk too to do not have some kind of glass under light that produce UV’s. You will need to wear UV’s 400 protection eye glasses that does protect against UVA and B’s and adequate clothing…
I wish you a Happy Growing…
~Al
@dbrn32 @Donaldj @peachfuzz @Countryboyjvd1971 @Covertgrower @MacGyverStoner 
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Thanks for joining the conversation, I didn’t realize where the extent of your knowledge came from until now.
I’m tapping out though. Everyone is free to spend their money however they’d like. Whether it makes sense to the rest of us, or not.
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Yeah, I understand, however it’s not a reason to reject our kindly advise with the back of her or his hand and praticly spit on them, but hey, like you said, it’s this person money and time and for now on I will back off and only gave she/he advise if she/he sollicitate me by tag… @dbrn32
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I probably mess with the “like” counter timer by hiting the “like” button to soon. … I am still or back at 1 hour before my likes are back , lol
I missed you too John , and thanks buddy
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