Do I need a dehumidifier if I have a space heater?

Question is basically in the title.

On this new grow I’ve added a space heater since winter is coming and I’m growing in the basement, I noticed with the space heater the relative humidity levels are around 35% (way lower than usual here) and so my dehumidifier never really went on, do I need it for this grow?

I heard that space heaters decrease the relative humidity but not the actual humidity, whatever that means. I’d like to remove my dehumidifier of I can so I can make for space for my plants. Should I?


Yada yada yada…


Humidity, specifically relative humidity, is really quite important. You’ll want to have a humidifier, as well as a controller (if you can afford one). 35% relative humidity, which will fall once you warm the air, is way too low for vegetative growth. I’d want to be at about 80f/75%RH.

Once bud sites really start to form many people in that situation (a basement) would want to bring the humidity down to 50% RH if the temperature is 80f. I don’t know. I feel like if you have good airflow through the canopy, you can avoid the problems of microclimates and dew.

TL&DR: you need a humidifier.


Make sure you get a controller, ink birds are great and this will help control your environment to narrow it in to a more accessible level.
Get a temp controller and attach it to your duct fan.
This will allow your environment to build up humidity when you need to raise it, if you need to drop it add a dehumidifier or your space heater whatever combo works.

Learn to control your humidity in line with your temp depending on your grow stage.

Google “cannabis VPD chart” post this on your phone or in your grow tent and refer to it on a regular basis.


I can not answer your question directly because it is impossible to answer it correctly. The only way to know is to get yourself a good humidastat and measure your humidity. You can not grow marijuana well if U do not know at all times what your humidity is and have complete control of it. Oh it will surely grow MJ is a tough weed but it will not have reached its kick ass potential.

1 Like

I have had two inkbird controllers. After operational learning curve. (Chinese translated into hinky English) I found that they were not stable in a 5X5 grow tent. They constantly drifted the temp setting after a time even after calibration. I am retired and my tent is in my home where I can keep a constant eye on it. I also had a Kestrel applied ballistics computer and environmental monitor with blue tooth in the tent to compare with the inkbird controllers. The Kestrel allowed me to constantly see temp and humidity on my android and it hardly ever matched the inkbird drifted enough that it would have caused heat stress if I had not been there to correct the temp discrepancy. The Kestrel is a $700.00 device and I am pretty sure it is accurate.

1 Like

What model of inkbird controller do you run?

Interesting, I have heard a lot of growers on here have success with very low humidity like that, maybe it’s not optimal but my seedlings so far are doing great under 35% RH. I was always more afraid of high humidity because of mold and shit and also because I live in an area where the humidity is regularly 50-70%. I could put a humidifier in there anyway but idk how well I’d be able to control it.

Also @Eaglesnester I have an AC Infinity fan in there so I can always see what the temp and humidity levels are from the electronic pad thing

Humidity is only an issue if inside the house above 50% you’ll grow mold in your house, of course no airflow as well.

You can grow in no humidity or lots of humidity but ideally you should understand VPD


1 Like

Ah yes, thank you for that chart, I do remember seeing it on here. However I guess I am technically in the danger zone since I’m at 35% RH and 77°. We’ll see how it goes though, my seedlings are doing great and the first transplant is coming up in a few days.

Anyways I think I got my answer…I can remove my dehumidifier, lol. Thanks for the all the help guys

1 Like

I vent into my basement instead of outside… So I need a dehumidifier to keep the humidity down in the basement… Otherwise in my tent I have an inkbird humidity controller with a humidifier in the tent and an exhaust fan connected to it.

I was getting lights off time high humidity… Like 92%…and things have been steady and consistent ever since.

1 Like

Controllers are a game changer,

1 Like