HUMIDITY AT NIGHT? TO PREVENT MOLD
- Thread starter Adi1989
- Start date
I L0VE W33D
Well-Known Member
Lot more experienced folk kicking around than I, but from what I've learned you don't want it any lower than 30%
stalebiscuit
Well-Known Member
my understanding is sufficient airflow is number 1 mold preventer
stalebiscuit
Well-Known Member
that mostly, they move air around enough to prevent spores from sticking
you can run a carbon filter too and use duct work if you have an oscillating tool or some way to cut a 3 inch or so square in the wall. will also cover smells too
this
plus
should be good
Renfro
Well-Known Member
that booster fan in the image is garbage.that mostly, they move air around enough to prevent spores from sticking
you can run a carbon filter too and use duct work if you have an oscillating tool or some way to cut a 3 inch or so square in the wall. will also cover smells too
this
plus
should be good
airflow helps prevent areas of higher humidity. Microclimates. Still if the air is humid you can move it all you like, it is still humid.
It is important to remember that PM likes RH% swings, low/high/low/high. So if you can avoid the extreme lows you are good to go in most cases, unless there is an existing infection, PM is hard to kill.
Botrytis is evil as it will strike your biggest buds, so I wanna be between 45 and 50% during later flowering.
stalebiscuit
Well-Known Member
ohhh im sure it sucks, i just google image searched
CannaOnerStar
Well-Known Member
Someone on another thread said that there is not much to worry unless it goes over 65rh at night. But i just found some budrot even tho i was below that, most likely due to picking up leafs from tight buds, which ended up releasing moisture inside the buds(this is just a theory, could be something else also), combined with really tight buds and bit too low airflow.
Unless you do something weird, your humidity will be higher at night than during day. During day about 45% rh is ideal, so 50% at night is good.
But the ideal humidity depends on your temperatures, higher temperatures allow for more moisture without causing mold.
Google VPD to get an idea how temperature and rh should go hand to hand during day hours and also keep in mind that lower temp = easier mold with same rh. Too dry compared to temperature doesent allow plant to photosynthesise properly, but this matter more during the day
Star Dog
Well-Known Member
If you go to low you'll invite other problems with the moisture getting sucked from the plant keep it around 48/52% rh
If you maintain the temperatures and use good ventilation the rh% will maintain itself.
Star Dog
Well-Known Member
Relative humidity is a measurement of how much water air can hold at a given temperature.
Cold air has a very limited ability to hold water, if you take a sample of air at 50f 80%rh and heat it to 77f its rh% will drop down to nearly half, I can't remember the exact figures but heating it has a dramatic effect in the it's ability to hold water hence rh%, % of moisture relative to heat.
Cold air has a very limited ability to hold water, if you take a sample of air at 50f 80%rh and heat it to 77f its rh% will drop down to nearly half, I can't remember the exact figures but heating it has a dramatic effect in the it's ability to hold water hence rh%, % of moisture relative to heat.
CannaOnerStar
Well-Known Member
Heat is movement at very small levels and cold things are still. If there is more heat, the water molecules are moving around more and thus dont start to condensate on surfaces as easily. Unless ofc the surface is a lot cooler compared to air, which is not the case with plants, except that they evaporate water, which might cool down things a bit, but that water is moving away and not condensating, unless there is a very poor air movement, then maybe.
Also if those water molecules are moving around rapidly, then there can be more of them in same space without them clumping together and wetting things. Also if surface of the plant is warm, it will shake and expell water molecules that also pick up this heat energy and start moving/vibrating.
I like to think it this way
p0opstlnksal0t
Well-Known Member
Exactly It's the swings that kill the room not the high humidity itself.
The best yields I've squeezed out of one of my rooms was when I ran 80° f and 70% RH from beginning to end. From the time the clones were dropped into their final pot until the time I chopped I kept the room at 80° and 70RH and the nighttime temp and humidity was exactly the same It's difficult to do but overall my plants looked the best yielded the best and stayed the healthiest from beginning to end in that one run I've had a hell of a time trying to mimic it now since it's a little difficult keeping nighttime temp and humidity exactly the same as lights on temp and humidity
Star Dog
Well-Known Member
I'm fussy with my rh and I have seen bits of bud rot, when I 1st started growing my set up was less than stellar, crap fans, cold night temps = high rh% and never had any bud rott, this is only a theory of mine but I think it's strain related?
I'm not Mr current affairs but I'm sure there's a few strains that are botrytis resistant... Anyone?
I'm not Mr current affairs but I'm sure there's a few strains that are botrytis resistant... Anyone?
Cinco
Well-Known Member
There are a lot of mold resistant strains. You can look them up. Many commercially developed and viable strains are mold and PM resistant. Resistant being the key, nothing is mold proof.
I have done runs at peak flower VPD at 80% RH and not had any rot issues. Plants love it. But I use multiple fans blowing under and through the canopy. Not just a gentle breeze, on max blowing air through the canopy. What most people would call too much airflow, probably. Never an issue on my end.
Where people have issues, in my pure opinion anyway, is with big swings as @Renfro said. 30c and 80% RH runs great if you maintain it... the plants grow like you would expect they would in a lush tropical equatorial rain forest.
However, like running anything at its max, there is less margin for error — when the temp swings down at lights out, you hit the dew point very quickly. At those room specs (30c, 80% RH)the dew point is only 26.2c. Only 3.8 degrees margin, or 12.6% temperature delta — below that, and all that moisture starts crashing out of the air and accumulating on the surfaces of everything. PM and mold love it.
So maintaining roughly the same vPD at a lower temp provides better buffer. At 20c and 60% RH, for example, the dew point is at 12c. 8c difference, and a much bigger margin at 40% delta needed to hit the dew point.
Just my thoughts from years of growing things, most of it not weed.
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Cinco
Well-Known Member
And for anyone interested, looking at dew point and temperature deltas needed to hit it can provide methods to mitigate PM and botrytis if you need or want a swing — ie, you don’t have to keep night time temps so high.
For example, if you can adjust your environmental controls to drop RH at 30c to even 65% RH (down from 80%) just before lights off, you expand that delta before dew point by a huge margin. Dew point drops to 22.7c and you safely allow temps to drop by several degrees.
For example, if you can adjust your environmental controls to drop RH at 30c to even 65% RH (down from 80%) just before lights off, you expand that delta before dew point by a huge margin. Dew point drops to 22.7c and you safely allow temps to drop by several degrees.