Is The Temp In My Grow Room Bad?


A customer has a question and I hope we can get some opinions on it, thanks.

“I just want to know if my temp in grow room is bad. It is between 69 to 79 degrees. I have to run a heater since it is cold in my basement. Also my RH is very low. Is that a problem?”


I think that is perfect, but a few strains prefer a little warmer climate!
For more information read this please


Your temperature is great, RH is very low for veg but great in flower and it’s much cheaper to increase the RH than it is to lower it, trust me.


Just hanging up some wet towels in the room would probably do it.


Sounds just like my grow tent. I, too, have to run a heater (kicks on mostly at night). I have the heater set up to keep the lows around 67 at night. It gets up to 81 with the lights on. I’ll likely turn the heater down a little bit once I get deeper into flower. My RH was abysmal - in the 30s. I added a wicking style humidifier for outside the tent to raise the RH in the basement in general. That got me up to 40% in the tent under the lights and in the 50s with lights off. So I then added a cool mist style humidifier directly in the tent. With both running I can get the RH under my canopy in the 60s and the RH above my canopy (below the lights still) in the high 40s low 50s.


I have my set up in basement as well my temps can get as low as 50 during the winter to combat this I recycle my air from tents instead of exhausting it out side
You can get a free stand evaporative type humidifier for about 60$ that would take care of low humidity situation in the winter the cool mist tyoe humidifiers are not the best and csn clog your filter system


Maybe adding a hps with low power can improve the temp.


HPS and LEDs are not really any different in terms of heating the room. Watts are watts and 600 watts of LEDS heat the room just the same as 600 watts of HPS. They may have a small difference in lumens per watt so the LED plants grow a bit faster, but we probably only get about 6% agricultural efficiency using the light and that’s only the light that falls directly on a leaf. All the rest of the light gets absorbed by the environment and turned into heat.


Not even close my friend… Led’s are good because them are not throwing a lot of heat.
The HPS is definitely produce a lot of :fire:.


I think his point is that if you compare actual watts they aren’t much different. If I put 4 of my cheap Chinese lights (260w actual consumption but 1500w advertised (150 10w diodes)) to get to 1000 watts the amount of heat it would produce would be similar to a 1000w MH/HPS fixture. The benefit of LED is that you could ideally get the same ppfd or better with fewer watts of consumption.


Yes: The HPS bulb will get very hot in a small area and the LEDs have big heat sinks that get warm over a large volume of air. But if you blow some air past the HPS bulb it will heat the room just the same as an equivalent wattage of LEDs. My HPS bulb made 133 lumens per watt and LEDs can be more efficient like about 170 lumens per watt, but most of them are not.

But it really makes no difference if they make a bit more light because that light almost all ends up as heat once it hits something. This is elementary physics: Watts = watts. They don’t magically appear and they don’t ,magically disappear.

The LED may make a spectrum you like better, but really the agricultural efficiency of cannabis is only about 6%. That means 6% of the photons that hit a leaf will go into photosynthesis, and all the rest is just turned into waste heat. So the differences between HPS and LED in terms of waste heat are very small.


I agree with you as far as it goes, but where led’s kick ass is with a diy build and the drivers stay out of your grow space. That’s a significant fraction of your overall power dissipation right there.

But you’re right: photons impinging on fixed surfaces will absorb them and get warmer. They don’t care whether they came from an led or an HPS bulb.


Drivers can live outside of your grow space and so can HID ballasts. It can actually be easier to get HID heat out of your grow space because most HID fixtures are ducted for easy connection to an exhaust fan. Most LED grow lights are not ducted, dumping all their heat right into the air of the grow space. Fortunately, hot air tends to rise so you can put an exhaust duct at the top. But of course if you have fans running then all the hot air gets mixed in.

My COB heat sinks are ducted and air flows over each set of fins and gets pulled out of the grow space.