Humidity Question

nomofatum · Jan 20, 2016

superbak3d said:
No, that chart is a guideline of what your RH should be at any given temp.

The orange is your recommended ranges, white is safe, anything in the blues will have negative results.

This is very important for certain growers that have to deal with extreme temp changes, mainly due to region. For instance, I am a far northern grower, it's dead of winter right now, and tents get cold fast. Southern growers might have to deal with much higher temps. Cannabis is very adaptable to it's environment.

So, with this chart. If I'm dealing with cold temps, under 60F, so long as my RH remains within 40-55%, my plants will not be harmed.

As you can see, the hotter your temps, the more narrow the optimal RH range becomes. If your temps are between 80-90F, you can still grow just fine, so long as you maintain a higher RH of 80-85%.

I run about 75f during lights on, about 60f during lights off. I live in the frigid north as well, my grow currently has the whole house at about 40% humidity. When it gets up to 50% the windows fog up. Without a grow going the RH would be 20-30 most of the winter. If I let humidity stay at 50% or higher, I will start to grow mold in my house. The buds will mold on less resistant strains.

Without the cool outdoor temps being able to condense the moisture on walls/windows I might be able to get away with higher RH, but the idea of following this chart in my conditions is ridicules. I would destroy my house and the bud with the recommended RH values from that chart.

In any case, I grow weed for the resin/thc, lower RH will lead to more resin. Higher RH will lead to a bigger/leafier plant.

Dr. Who · Jan 20, 2016

nomofatum said:
I have to say I'm not liking that chart at all.

If I'm reading that correctly it says 60-80 RH in the lights on temp range and 45-55 in lights out temp range. If I ran at those RH values, I would expect at least half of my bud to be moldy. The windows in the house would ice shut from humidity.

Low RH also is a stimulant for cannabis to produce more resin. UVB and dry conditions require the plant to protect itself with resin.

I run in 30-40 RH, then drop it into the 25-30 RH for the final week.

I run lower too....around 40 -50, chart be damned......I do like posting it though.......Newbies learn something.......I don't like the rh low as you run. Don't agree with high transpiration "pushing".....Increase trich's and terps with Mg and S and UV I played with some years ago....Don't find it as cost effective on my scale ...Reptile bulbs don't penetrate enough to warrant real time use by the average grower = 18 inch's ain't shit! To get somewhere really, you need to jump up to 400w Merc Vaper bulbs in wings! NOW your adding UVB! Still not cost effective in my book - adding more cost then benefit.
The new dual arc bulbs supply 600w HPS and 400w MH in a single 1k bulb.....That may have almost as much effect as your UV for what your looking for.....Got a set coming-going to try them. Plantmax duals are 1/3 the price of the EYE Horts at 1000bulbs.com

nomofatum · Jan 20, 2016

Dr. Who said:
I run lower too....around 40 -50, chart be damned......I do like posting it though.......Newbies learn something.......I don't like the rh low as you run. Don't agree with high transpiration "pushing".....Increase trich's and terps with Mg and S and UV I played with some years ago....Don't find it as cost effective on my scale ...Reptile bulbs don't penetrate enough to warrant real time use by the average grower = 18 inch's ain't shit! To get somewhere really, you need to jump up to 400w Merc Vaper bulbs in wings! NOW your adding UVB! Still not cost effective in my book - adding more cost then benefit.
The new dual arc bulbs supply 600w HPS and 400w MH in a single 1k bulb.....That may have almost as much effect as your UV for what your looking for.....Got a set coming-going to try them. Plantmax duals are 1/3 the price of the EYE Horts at 1000bulbs.com

My understanding is that the plant adapts to the RH or UV light by producing more resin to line the outside of the leaves and stem. That resin reflects UVB light and it also acts as a moisture barrier. It's the plants natural way to reduce transpiration by adapting to the environment.

I have seen some intense UVB results. The first time I ran a reptile 10.0 UVB CFL, I ran it between two autos, the sides facing toward the bulb were significantly frostier and you could see that every tric point at the bulb. You can't really get UVB to "penetrate" as levels that high would kill the plants. UVB just makes the colas extra potent and pretty.

I would never tell anyone to run higher than 50 RH when it's cold outside or 60 RH when warm. They are too likely to destroy their home or their bud at those levels.

My UVB for 32 sqft cost me about $80. 200w UVB 9.9 tanning bulbs ($30), workhorse 8 ballast ($35), bulb connectors ($5) and some spare wood, mylar and wires.

Dr. Who · Jan 20, 2016

nomofatum said:
My understanding is that the plant adapts to the RH or UV light by producing more resin to line the outside of the leaves and stem. That resin reflects UVB light and it also acts as a moisture barrier. It's the plants natural way to reduce transpiration by adapting to the environment.

I have seen some intense UVB results. The first time I ran a reptile 10.0 UVB CFL, I ran it between two autos, the sides facing toward the bulb were significantly frostier and you could see that every tric point at the bulb. You can't really get UVB to "penetrate" as levels that high would kill the plants. UVB just makes the colas extra potent and pretty.

I would never tell anyone to run higher than 50 RH when it's cold outside or 60 RH when warm. They are too likely to destroy their home or their bud at those levels.

My UVB for 32 sqft cost me about $80. 200w UVB 9.9 tanning bulbs ($30), workhorse 8 ballast ($35), bulb connectors ($5) and some spare wood, mylar and wires.

"Penetrate" as in effective distance from the bulb......Reptile lights are made to work only 18" - The distance from large tanks lighting hoods to the surface of the floor. Federal safety issue ( How nice of them). Same thing for tanning bed bulbs...controlled effective wavelength distance...

UVB thc levels can rise as much as about 10 or so %...Like about 2 to 4 point rise and I got like a 2.3 point average rise in better strains... I got these results using the 400 Mec vapor's......Trust me, i don't and won't argue UVB effectiveness!

Like I said, not cost effective for me. 9.4 times the size of yours! I grow 5+ ft tall too....there comes that penetration issue.

nomofatum · Jan 20, 2016

Dr. Who said:
"Penetrate" as in effective distance from the bulb......Reptile lights are made to work only 18" - The distance from large tanks lighting hoods to the surface of the floor. Federal safety issue ( How nice of them). Same thing for tanning bed bulbs...controlled effective wavelength distance...

UVB thc levels can rise as much as about 10 or so %...Like about 2 to 4 point rise and I got like a 2.3 point average rise in better strains... I got these results using the 400 Mec vapor's......Trust me, i don't and won't argue UVB effectiveness!

Like I said, not cost effective for me. 9.4 times the size of yours! I grow 5+ ft tall too....there comes that penetration issue.

This again is a common case of misunderstanding. The levels of UVB drop according to the inverse square law just as every other light does. It also has the same limitation as the inverse square law in a confined/reflective space (note that white does not reflect UVB, so wall must be mylar to effectively use UVB.) In a confined reflective space, the light can only spread outward until reflecting off the walls. So the inverse square law is limited to the spread of your floor space. Example, if a light is 1 ft away and projects a 1 sqft footprint it will be said to be at full strength. Now if the room is 4x4 and the light is 4ft up the light will spread to the full 16 sqft, if the light is raised another 1 ft the light will not diminish in strength at all (except the tiny loss of the reflector), so it will still be 1/16th as bright as the 1 sqft, not the 1/25th that the inverse square law would lead you to believe. This is because the inverse square law is based on the assumption that you are in an unconfined space.

In the case of UVB, the light isn't absorbed by the air within 18", it just spreads to the point where 1 bulb can't keep a reptile healthy past that range because the levels will have dropped too much. Now if you lined the outside of a 18"x18"x72" box with mylar, and put the UVB bulb all the way at the top, the reptile would still be healthy 72" below because light levels would still be the same.

200w of 9.9 tanning over 32sqft puts me just a bit higher than the average UVB dose in the Hindu Kush Mountains.

The effects you see from a 400 merc vapor is most likely from UVA and deep blues. UVB light is easily blocked by more than 1 layer of glass, if you have a bulb with 2 layers of glass or use a fixture with a layer of glass, the UVB output of any HID bulb is effectively zero. The nice thing with tanning bulbs is they put out UVA, UVB, and Deep blues but nothing else.

With tanning bulbs and DIY fixtures it's so cheap you can't afford not to do it, lol. In your case it would be even a better deal, I would just buy a used tanning bed (can be found for $100 often on craigslist) and a new set of bulbs and a few 1x6 boards and mylar. I bet you could have your much larger space outfitted the same as mine for less than $400.

tyke1973 · Jan 20, 2016

Deathhasnofriends said:
Just curious how low my humidity can be in my flower room I'm running 2 1000 watt air cooled hoods exhausted by a 6" inline fan with a carbon filter. The fan is set on low also 6" inline intake fan also set on low pulling in fresh air through a hepa filter. With a 16" oscillating fan my temps hi is 81℉ and low is 66℉ humidity high 53% RH humidity low 27% RH when the lights go out the humidity climbs when my exhaust fan kicks on it sucks the humidity right out even on the lowest setting. Here is a picture of my tent setup.

Move the lights closer to each other dude,pretty much the same set up has i run in one property,or where the duct is in the middle put a cool tube not hood,but still move them ,closer ya losing a lot of light on the left hand right hand walls ,have a look at the terminator line it will be a fair way up the tent side,by moving the lights closer the light will be spread far more.The cool tube in the center is a great addition,just flip it on about week 4 or 5 on wards the over all yeild will increase a lot,if you are using,a decent exaust fan think there 8" if there,same size hoods has mine but i run a 12 " out let for the reason of the extra light ,i never been lower than 40% humidity so would not know about any lower they ,did ok but normaly its around 50/55 %.I also think that this will lower the temp's try to use has less duct has you can get away with,the only time i would use that much duct is if i was running plants at different phases,but still have the duct in between the lights a lot less,you have got the light there any how 2 x 1000's but honest i think you will see a big difference in the light if there moved closer to each other

Deathhasnofriends · Jan 20, 2016

tyke1973 said:
Move the lights closer to each other dude,pretty much the same set up has i run in one property,or where the duct is in the middle put a cool tube not hood,but still move them ,closer ya losing a lot of light on the left hand right hand walls ,have a look at the terminator line it will be a fair way up the tent side,by moving the lights closer the light will be spread far more.The cool tube in the center is a great addition,just flip it on about week 4 or 5 on wards the over all yeild will increase a lot,if you are using,a decent exaust fan think there 8" if there,same size hoods has mine but i run a 12 " out let for the reason of the extra light ,i never been lower than 40% humidity so would not know about any lower they ,did ok but normaly its around 50/55 %.I also think that this will lower the temp's try to use has less duct has you can get away with,the only time i would use that much duct is if i was running plants at different phases,but still have the duct in between the lights a lot less,you have got the light there any how 2 x 1000's but honest i think you will see a big difference in the light if there moved closer to each other

So your saying I should add another light the cool tube reflector?

Deathhasnofriends · Jan 20, 2016

tyke1973 said:
Move the lights closer to each other dude,pretty much the same set up has i run in one property,or where the duct is in the middle put a cool tube not hood,but still move them ,closer ya losing a lot of light on the left hand right hand walls ,have a look at the terminator line it will be a fair way up the tent side,by moving the lights closer the light will be spread far more.The cool tube in the center is a great addition,just flip it on about week 4 or 5 on wards the over all yeild will increase a lot,if you are using,a decent exaust fan think there 8" if there,same size hoods has mine but i run a 12 " out let for the reason of the extra light ,i never been lower than 40% humidity so would not know about any lower they ,did ok but normaly its around 50/55 %.I also think that this will lower the temp's try to use has less duct has you can get away with,the only time i would use that much duct is if i was running plants at different phases,but still have the duct in between the lights a lot less,you have got the light there any how 2 x 1000's but honest i think you will see a big difference in the light if there moved closer to each other

One like this

Dr. Who · Jan 21, 2016

nomofatum said:
This again is a common case of misunderstanding. The levels of UVB drop according to the inverse square law just as every other light does. It also has the same limitation as the inverse square law in a confined/reflective space (note that white does not reflect UVB, so wall must be mylar to effectively use UVB.) In a confined reflective space, the light can only spread outward until reflecting off the walls. So the inverse square law is limited to the spread of your floor space. Example, if a light is 1 ft away and projects a 1 sqft footprint it will be said to be at full strength. Now if the room is 4x4 and the light is 4ft up the light will spread to the full 16 sqft, if the light is raised another 1 ft the light will not diminish in strength at all (except the tiny loss of the reflector), so it will still be 1/16th as bright as the 1 sqft, not the 1/25th that the inverse square law would lead you to believe. This is because the inverse square law is based on the assumption that you are in an unconfined space.

In the case of UVB, the light isn't absorbed by the air within 18", it just spreads to the point where 1 bulb can't keep a reptile healthy past that range because the levels will have dropped too much. Now if you lined the outside of a 18"x18"x72" box with mylar, and put the UVB bulb all the way at the top, the reptile would still be healthy 72" below because light levels would still be the same.

200w of 9.9 tanning over 32sqft puts me just a bit higher than the average UVB dose in the Hindu Kush Mountains.

The effects you see from a 400 merc vapor is most likely from UVA and deep blues. UVB light is easily blocked by more than 1 layer of glass, if you have a bulb with 2 layers of glass or use a fixture with a layer of glass, the UVB output of any HID bulb is effectively zero. The nice thing with tanning bulbs is they put out UVA, UVB, and Deep blues but nothing else.

With tanning bulbs and DIY fixtures it's so cheap you can't afford not to do it, lol. In your case it would be even a better deal, I would just buy a used tanning bed (can be found for $100 often on craigslist) and a new set of bulbs and a few 1x6 boards and mylar. I bet you could have your much larger space outfitted the same as mine for less than $400.

Not arguing = explaining my position OK?

The power and out put design of repti bulbs are set for low distance effectiveness - I called the makers years ago and had the discussion with them.....Yes the square inverse law is part of their computations... I tend to believe engineers.

Merc vapors DO Put out LARGE amounts of UVB and include quite specific FEDERALLY MANDATED WARNINGS right on the packaging! Merc vapors are intended to be on the endangered list by gov intervention! The FED is looking to possibly ban them and require the no manufacturing of them directly for the reason of the UV emissions ! This has slipped in the last few years to a back burner from pressure from the industry. Info from engineers at GE..They state that for the purpose I proposed to use them. To where eye protection from the concentrated UV present. I was also warned that they may tend to "overexpose" the plants and kill them in short order......I experimented with that too. It did and I came to run them for short times during my lighting sched. The most pronounced effect was when run about 2/3's of the way through the on time and for no less then 10 min and no more then 20.......
Note to ponder. The plant I "cooked" to death with the UV was, well,,,,,blinding in effect......I achieved the same effects by the controlled exposure too!

However, you are correct that the borosilicate glass used in the bulb's, does reduce UV emission (another Fed regulation as per discussion with engineers at EYE - This point even carries over to your window glass by coatings and content!). They do say that even with that in mind, you can get some from simply removing the glass sheet from your hood and using a MH bulb for your last weeks before harvest! Not a lot mind you, and less then the sun but, they state that enough to actually make a difference!

I have to ask this as I'm kind of interested......How many watts per bulb and can you find me the running amps of one too? Like maybe meter it if you have one..

GREAT BACK AND FORTH discussion!

If you like we could take this PM.....WAIT!!!!

We better not, I'm sure this is getting attention of interested parties.....My other UV discussions did a lot!

mandy1 · Jan 21, 2016

i use a couple of cheap chinese foggers in a 5 gallon bucket with an occellating fan blowing over the top of the bucket. while my room rh stays around 50%, the humidified air blowing over my girls is 70%. you could probably rig some kind of fogger in your tent. here's a good article on what to look for in your leaves for temp or humidity problems. the article is in spanish but if you have windows, you can r click for a translation option. http://www.lafamiliacannabica.com/2015/11/10/sintomas-de-deshidratacion-en-la-marihuana/

mandy1 · Jan 21, 2016

PS- that vpd chart on the first page should be copied, laminated and placed in every grow room. its that important to having healthy plants. good air circulation is the key to avoiding mold/mildew.

nomofatum · Jan 21, 2016

Dr. Who said:
How many watts per bulb and can you find me the running amps of one too? Like maybe meter it if you have one..

The tanning bulbs I run are 100w each and 71" in length. They can run on a wide variety of power conditions, but typically at 200-600v.

When running 2 of them the killawatt reads 206w vs 208w (I have two of these setups.)

Wall Amps: .9a each (assuming 115v/120v version ballast)
Bulb Volts/Amps: I believe it's 600v so it would be .17a each (.34a for both) from ballast to bulb.

ryan1918 · Jan 21, 2016

Deathhasnofriends said:
Just curious how low my humidity can be in my flower room I'm running 2 1000 watt air cooled hoods exhausted by a 6" inline fan with a carbon filter. The fan is set on low also 6" inline intake fan also set on low pulling in fresh air through a hepa filter. With a 16" oscillating fan my temps hi is 81℉ and low is 66℉ humidity high 53% RH humidity low 27% RH when the lights go out the humidity climbs when my exhaust fan kicks on it sucks the humidity right out even on the lowest setting. Here is a picture of my tent setup.

if your flowering it varies in what week your in as what your humidity should be, I keep mine at 45-50 during the first 4 weeks and the last 3-4 weeks keep dropping it 5% each week until it's at 35 or so to prevent any mold specially when my lights go off since the temps drop to 58-60*

Dr. Who · Jan 22, 2016

nomofatum said:
The tanning bulbs I run are 100w each and 71" in length. They can run on a wide variety of power conditions, but typically at 200-600v.

When running 2 of them the killawatt reads 206w vs 208w (I have two of these setups.)

Wall Amps: .9a each (assuming 115v/120v version ballast)
Bulb Volts/Amps: I believe it's 600v so it would be .17a each (.34a for both) from ballast to bulb.

Thank you nomo for the information!
I may just play with a set and do some testing at several plant levels.
I must be partly Burmese cat. Hugely curious and always wanting answers to why.......Your tanning bulbs have me interested in UV again......I have already envisioned a set on either side of my HID hoods...

So do you run those constant or timed during your lighting time? Ever measure (test) the THC concentrations against non exposed plants?

theslipperbandit · Jan 22, 2016

Great discussion lads very informative

BiG PuFFer · Jan 22, 2016

ryan1918 said:
if your flowering it varies in what week your in as what your humidity should be, I keep mine at 45-50 during the first 4 weeks and the last 3-4 weeks keep dropping it 5% each week until it's at 35 or so to prevent any mold specially when my lights go off since the temps drop to 58-60*

Im at week 4 of flower. I was having day humidity at around 35-40%. Now im getting 80% when the lights come on. So i been running the fan 24/7 and humity is in the 20's. Is that too low? How can i add some more humidity in a cramped tent? Im thinking turning the fan down with a controller will alow more moisture to stay in the room. But I've also had bud mold before and want to avoid it all cost.

nomofatum · Jan 22, 2016

Dr. Who said:
So do you run those constant or timed during your lighting time? Ever measure (test) the THC concentrations against non exposed plants?

I haven't tested any of my plants yet. I would like to, but being illegal, I have not. I'm curious if any decent home testing options exist...

I've done 30on 30off repeating all day, I've done 4 hours around noon, and I've done the full 12 hours. It's difficult to tell a difference visually. It's easy to see the difference of with vs without, but not easy to differentiate based on the hours/timing.

I'm currently running them the full 12 and will be replacing bulbs with about 2 weeks to go.

superbak3d · Jan 22, 2016

I never grow anymore without the use of additional UVB.

I love frosty buds

BiG PuFFer · Jan 22, 2016

superbak3d said:
I never grow anymore without the use of additional UVB.

I love frosty buds

What are you using?

ryan1918 · Jan 22, 2016

nomofatum said:
I run about 75f during lights on, about 60f during lights off. I live in the frigid north as well, my grow currently has the whole house at about 40% humidity. When it gets up to 50% the windows fog up. Without a grow going the RH would be 20-30 most of the winter. If I let humidity stay at 50% or higher, I will start to grow mold in my house. The buds will mold on less resistant strains.

Without the cool outdoor temps being able to condense the moisture on walls/windows I might be able to get away with higher RH, but the idea of following this chart in my conditions is ridicules. I would destroy my house and the bud with the recommended RH values from that chart.

In any case, I grow weed for the resin/thc, lower RH will lead to more resin. Higher RH will lead to a bigger/leafier plant.

What kind of yield do you get with them temperatures?

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