Cold and high RH. Buy an extra Heater to solve both issues?

I have a 4x4 grow tent in my bedroom. It's winter now where I live and the room stays at 20C - 21C (69F) and 50 - 60% RH. I have to open the windows to bring the RH down to the 40% range, but it can get cold quick. The lights go on at 7pm til 7am. Even with the lights on, the temperature doesn't go above 22C (71F) and the RH can spike up to 65-70% especially as I'm using a drip to waste system to water. I grow under 550w LED lights. I never had this problem when I grew with HPS.

I already bought an dehumidifier from Amazon which doesn't help. Now I'm wondering if a small heater can effectively decrease the RH? If so, any tips what kind of a heater I should buy? I'm not looking to spend a lot.. probably around 100- 150 USD. I really hope this can solve both issues at once.

I read oil radiator heaters work great. I think they make mini ones. I used a ceramic blower heater and it helped reduce night humidity drastically. I noticed once the plants woke up they quickly transpired enough to get it humid again though. The ceramic blower did really dry some leaf’s out though I would get a radiator one.

maybe run heater on a heat controller, and run the dehumidifier during the day. I suggest getting a cheap humidity and temp logger to have an extra set of eyes. I picked up a gsp-6G from elitech Was like $40 or something. See when they need to run the most.

Regardless of all that, it would be real nice to get that temp above 76. Be better around 80 Ish.

For heat, i use Honeywell Heat Bud Ceramic Portable-Mini Heater, HCE100. It's 150/250w and heats the outdoor shed (I use a itc-308 inkbird for heat control). My space is 16sq ft.
The 50-60% humidity should fine unless the strain hates humid air.

Personally I prefer to fiddle with intakes and exhausts. Having an open window and a heater/dehumidifier sounds.. dumb. Also, there's no reason to be bringing in all that cold air to keep the around 40. I know that's what we used to say but a lot of people (myself included) are finding even flowering plants prefer it above 50

A heater won't solve your RH problem. Which dehumidifier did you get? You need a proper one with compressors-the little thermo-electric ones don't work well. A compressor dehumidifier will heat a small room (to some extent) and dehumidify.

What is your lighting? Stick a 315 CMHin there during cold months.

Running LEDs close to plants will help, especially with leaf temps but you must be careful.

MyBallzItch said:

Personally I prefer to fiddle with intakes and exhausts. Having an open window and a heater/dehumidifier sounds.. dumb. Also, there's no reason to be bringing in all that cold air to keep the around 40. I know that's what we used to say but a lot of people (myself included) are finding even flowering plants prefer it above 50

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I don't keep the window open for too long. I just mentioned it as that's the only way I've been able to bring the RH down.

hillbill said:

What is your lighting? Stick a 315 CMHin there during cold months.

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Optic 8+ LED. Thats a 550w COB LED. Unfortunately I don't have enough space in my 4x4 tent for an additional light

Rurumo said:

A heater won't solve your RH problem. Which dehumidifier did you get? You need a proper one with compressors-the little thermo-electric ones don't work well. A compressor dehumidifier will heat a small room (to some extent) and dehumidify.

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I bought one on Amazon for like 70$. It had good reviews so I ordered it. I put it in the tent, outside the tent where the intake is... but it does nothing.

HPS for winter,led for summer.

A heater could help, just depends if the room holds the heat. As temps increase the amount of moisture the air can hold also increases, that's why it's called "relative humidity" so if u get the temps up the humidity may decrease. Also dehumidifiers work better as it gets warmer. What dehu did you buy?
Are there windows in this room? If they're old maybe cover them up with plastic and then a heavy blanket to keep the heat in.

Rurumo said:

A heater won't solve your RH problem. Which dehumidifier did you get? You need a proper one with compressors-the little thermo-electric ones don't work well. A compressor dehumidifier will heat a small room (to some extent) and dehumidify.

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This is straight bullshit and exactly backwards. Any meteorologist will tell you that in order to reduce RH you must ADD HEAT.

At least do a bit of research before "helping" people like this.

Are you running the light at full? Is it "rated" at 550W or does it actually pull that much from the wall?

Adding heat is a good idea. The guy above who said you want it to be 80F in the tent is correct. I'd actually suggest 85F for good plant metabolism and growth.

You need heat and you need insulation. The guy above who said to insulate your room is correct. How is the room heated? If hot water baseboard heat then insulating the room should help a lot. If forced air then you'll have smell problems but it will help warms the room and dehumidify. If you're having problems, the vent may be blocked.

If insulating the room isn't enough, then you need a heater. What kind matters less than whether it can run on a thermostat, either internal or external. Don't aim it at the tent or the plants; you'll fry them.

A dehumidifier really is a heater in disguise. Since you already have one, you may as well use it. Again, adequate room insulation is key and you want it warm.

Are you saying the room the tent is in spikes up to 65-70 when lights are on (overnight)? And Is the 71 degrees the temp of the tent or the room the tent is in? Sorry if this is a dumb question but I'm high and reading it a second time is bringing up these questions lol

ttystikk said:

This is straight bullshit and exactly backwards. Any meteorologist will tell you that in order to reduce RH you must ADD HEAT.

At least do a bit of research before "helping" people like this.

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Really? Airconditioning can't lower humidity, heat must be added?
Is that why most growers use dehumidifiers?
What does one do if the temp is 30C and the humidity is too high?

1212ham said:

Really? Is that why most growers use dehumidifiers?

What does one do if the temp is 30C and the humidity is too high?

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Up north we use dehumidifiers down south go AC, Dehuys put out tons of nice dry heat

Rurumo said:

A heater won't solve your RH problem. Which dehumidifier did you get? You need a proper one with compressors-the little thermo-electric ones don't work well. A compressor dehumidifier will heat a small room (to some extent) and dehumidify.

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Small electric heater will dry things right out If one can handle the heat.

The humidity is coming from your plants, not the air outside your tent.

People are willing to pay $800 for a good LED but cheap out on a dehumidifier. I can understand it because at first your plants are small and there's no transpiration to speak of so everything is aok. But as they grow, they start pumping out water at a good clip. A healthy plant can transpire 80% of the water you give it. So if you have 4 big plants, water running down the walls of your tent will be an issue.

greenops said:

I have a 4x4 grow tent in my bedroom. It's winter now where I live and the room stays at 20C - 21C (69F) and 50 - 60% RH. I have to open the windows to bring the RH down to the 40% range, but it can get cold quick. The lights go on at 7pm til 7am. Even with the lights on, the temperature doesn't go above 22C (71F) and the RH can spike up to 65-70% especially as I'm using a drip to waste system to water. I grow under 550w LED lights. I never had this problem when I grew with HPS.

I already bought an dehumidifier from Amazon which doesn't help. Now I'm wondering if a small heater can effectively decrease the RH? If so, any tips what kind of a heater I should buy? I'm not looking to spend a lot.. probably around 100- 150 USD. I really hope this can solve both issues at once.

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What dehu did you buy? How much water is it removing? I'm guessing it's thermoelectic and they don't do much.

Anyway, let's figure this out. What is your exhaust and intake setup? Whats the humidity in other parts of the house?