Best humidity level using LED?

[Dr. Frescho]

Ey rollitup, so i've been wondering if during flowering the humidity levels with a LED should be the same as with a HPS... 40-50%
Do i need to have higher humidity like 60% just because i'm using a LED?
Or there's really no difference and i'm just trippin balls?

 

[Grow So High]

You are trippin balls haha I would suggest sticking with 40-50 in flower, I personally keep mine around 30-40. Same chances of getting mold in the 60-70 range regardless of the light

 

[meangreengrowinmachine]

In veg I use a much higher humidity with leds but like @Grow So High said I would not risk much then 40 or 50.

 

[Dr. Frescho]

I was asking this because from what i know, and now i get a little bit scientific aka trippin balls...

The best photosynthesis of the plant is achieved when the leaves reach a LST (Leaf Surface Temperature) of 27/29 degrees,that's when you have normal CO2 parameters in your grow room (400/700 PPM)

So, the HPS lights will give more LST to the plant, that's cause they release IR radiations that will heat up the surface of the leaves 2 to 3 degrees more compared to a LED, that doesn't release IR radiations.

So let's say we have a growroom with flowering plants, the temperature at lights on in the grow room is 25 degrees; with a HPS there's no problem because as i said the HPS will heat up the surface more raising the temperature of the leaves from 25 to 27/28, resulting in a perfect photosynthesis.

When we have a LED tho, the situation changes, because let's say we always have the grow room with 25C of temperature in flowering stage; since the LED doesn't heat up the leaf surface, as the HPS do, we'll have to raise the grow room temperature to 27/28, but by doing so we'll have to raise also the humidity.

That's because humidity should change according to the temperature of the grow room.As you can see in the diagram here humiditi vs temperature and VPD

 

[meangreengrowinmachine]

I was asking this because from what i know, and now i get a little bit scientific aka trippin balls...

The best photosynthesis of the plant is achieved when the leaves reach a LST (Leaf Surface Temperature) of 27/29 degrees,that's when you have normal CO2 parameters in your grow room (400/700 PPM)

So, the HPS lights will give more LST to the plant, that's cause they release IR radiations that will heat up the surface of the leaves 2 to 3 degrees more compared to a LED, that doesn't release IR radiations.

So let's say we have a growroom with flowering plants, the temperature at lights on in the grow room is 25 degrees; with a HPS there's no problem because as i said the HPS will heat up the surface more raising the temperature of the leaves from 25 to 27/28, resulting in a perfect photosynthesis.

When we have a LED tho, the situation changes, because let's say we always have the grow room with 25C of temperature in flowering stage; since the LED doesn't heat up the leaf surface, as the HPS do, we'll have to raise the grow room temperature to 27/28, but by doing so we'll have to raise also the humidity.

That's because humidity should change according to the temperature of the grow room.As you can see in the diagram here humiditi vs temperature and VPD

Right but imo that humidity increase in flower to such high levels is just too much of a mold risk. In veg I absolutely go that high and for the exact reasons you have sited. I guess I am not sure how most LED growers balance this in flowering.

 

[Dr. Frescho]

Right but imo that humidity increase in flower to such high levels is just too much of a mold risk. In veg I absolutely go that high and for the exact reasons you have sited. I guess I am not sure how most LED growers balance this in flowering.

I'm using a LED so that's why i'm wondering this, i guess if i go with 28C in the grow room with 60/65% of humidity it should be fine, what do you say?

Right now i have the humidity set at 45/50% because i'm too scared for mold problems, since most sites says that anything over 60% of humidity during flower is mold guaranteed...

 

[Grow So High]

I use LEDs and keep a humidity probe by the canopy with an average temperature between 78-80 in flower. I keep my humidity around 35 with no growth issues. I understand now why you want to raise the humidity but regardless of the light, having the humidity that high definitely increases the chance of mold. If you really want to run it around 60-65 which many people swear by just make sure you have really good airflow

 

[meangreengrowinmachine]

I'm using a LED so that's why i'm wondering this, i guess if i go with 28C in the grow room with 60/65% of humidity it should be fine, what do you say?

Right now i have the humidity set at 45/50% because i'm too scared for mold problems, since most sites says that anything over 60% of humidity during flower is mold guaranteed...

I would stay right at that range personally.

 

[ancrib]

I have led lights and I will stick with gradually decreasing the rh in the flower. Yes, I saw a difference in growth while having higher rh and temps but not worth the risk to go full flowering cycle with 60% , I still make tests myself but the bud it feels too moist at 60+%. Make some tests yourself and see how is it going but still I'll not go over 60%...

 

[Dr. Frescho]

MMMh yeah i think i'll stick with 45/50, this is my frist grow and the last thing i want is mold...
Thanks guys

 

[Castrau5]

I stick to the vpd chart in all my grows with great results. I gotta have proper air flow and canopy management to run this way but if you do you wont regret it.

If your not getting 1 gram per watt you should consider trying

 

[MICHI-CAN]

I run 60-65% in veg. I drop to 35-50% in flower. Prefer 40-45%.

 

[P10p]

I think most people use that VPD chart as a general guide for veg, not flower.

 

[Dr. Frescho]

I think most people use that VPD chart as a general guide for veg, not flower.

Yeah that's what i thought too, now i'm keepin humi at 40/45, even tho photosynthesis is better using that chart, using it during flowering may results in diseases so i'll follow that during veg only i guess...