I have mine set to be “Lights On” only at night for several reasons
- In winter, the coldest time is at night, and the heat from the grow lights (LED) keeps the tent warm
- In summer - it is easier to keep the heat DOWN at night
But there is a third factor that comes into play, and it is Relative Humidity (RH). At night, with cooler temperatures, the RH is higher than in the daytime. Also - when my cooling fan is running it drives the moist air that I run an Inkbird controlled humidifier to create out of the tent so that the humidifier has to work harder to keep it in range.
Have a look at this chart:
Someone here posted that, and it gives us a very good idea where we want the humidity to be at different temperatures. As you study it, you notice that at higher temperatures the RH has to increase as well. It also seems to me that around 75 f. (roughly 20 C.) is the ideal, and it is also fairly do-able inside a house or apartment without breaking the bank on air conditioning running up the power bill.
But at that temperature the ideal is between 55% to 65% RH.
70 degrees f. is five percent lower, and much easier on the humidifier. It’s refilling the humidifier with gallon after gallon of water that gets to be annoying.
Now let’s have a look at this:
On the upper right of that weather site, you can select Humidity as what you want to look at
using the time slider on the bottom of the display you can look at changes throughout a 24 hour period for days ahead, and see what the humidity does overnight, and also temperature
What I have found is that if my lights are OFF between the hours of 9AM and 6PM the natural humidity is closest to what I want it to be. That is of course a 15 hour “Lights On” period - it can be extended to 16 or 18 hours if you like, but that is the ideal time frame to make the most of cooling and ambient air humidity
When the lights are off during the day, the cooling fan as I have it set up (the vent fan is controlled by an Inkbird Temperature Controller) seldom comes on at all. I may need to add one more vent fan because the other thing that happens is with the lights off during the day I have seen the RH in the grow tent rise well over 80% at times
That can be corrected by connecting a second vent fan to the “De-Humidifying” connection on the Inkbird RH controller, which has one connection for a humidifier and another for a DE-humidifier
Venting off the excess humidity with a fan is all I need to do, there is no need to dump huge cash into a complicated and expensive Dehumidifying machine
But this is the setup that I am running with now and enjoying huge success! The plants love it. I keep a gallon and a half pump sprayer in the tent for emergencies, or when in the Vegetative stage I want to mist my plants frequently.
Just now I have a four foot by eight foot tent, 80 inches tall, and 4500 Watts (equivalent) Morsen LED arrays supplying light energy so the heat given off is considerable
What it comes down to, Lads and Lasses, is a balancing act. But by running everything at the best time of day (or in this case NIGHT) it is much more manageable…