Humidity Too High??

Here's my current weather at 6:30 am.

Temp/RH
Outside: 62F/91rh (raining)
Garage where tent is: 68F/60rh
In 3x3x7 foot tent: 72F/69-77rh

My White Widow autoflowers are starting to flower now and I'm concerned that the RH is too high and I don't know what to do. I have two 6" fans blowing inside. If I run the exhaust fan constantly it helps but the temp drops too much especially on colder nights.
I've considered a dehumidifier but floor space is limited.
I'm already running a continuous light cycle to try and control things better.
Any ideas what I can do?

Hey Tedeboy,.yeah you'll have to try and get that RH down or you'll end up with either PM, mould or both. The air outside the tent is 60RH which isn't great but better than 70+ inside. If you can bring more of that air in and exhaust you should be able to reduce it. But imo you're looking at a de-humidifier. Options: Bring in dryer air, exhaust more (sounds like you're already doing that), de-humidifier. Also, your temps are a little low so you have room to increase the temps, that will also bring down RH. Cheers.

GroErr said:

Hey Tedeboy,.yeah you'll have to try and get that RH down or you'll end up with either PM, mould or both. The air outside the tent is 60RH which isn't great but better than 70+ inside. If you can bring more of that air in and exhaust you should be able to reduce it. But imo you're looking at a de-humidifier. Options: Bring in dryer air, exhaust more (sounds like you're already doing that), de-humidifier. Also, your temps are a little low so you have room to increase the temps, that will also bring down RH. Cheers.

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What size dehumidifier? I'm not sure I can fit it but I'll try.
Also, when the exhaust fan comes on (thermostat) won't that negate the dehumidifier's effectiveness or would that be temporary until it turns off? I could have the exhaust come on less to bring the temp up but some days it's warm in the garage so the exhaust would come on a lot more.

TedeBoy said:

What size dehumidifier? I'm not sure I can fit it but I'll try.
Also, when the exhaust fan comes on (thermostat) won't that negate the dehumidifier's effectiveness or would that be temporary until it turns off? I could have the exhaust come on less to bring the temp up but some days it's warm in the garage so the exhaust would come on a lot more.

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Not sure on the sizes out there as I haven't looked around for one for a long time. It's a relatively small area so a small one would be fine. Only issue with humidifiers is draining them so if you can find one that has like a tap/drain tube and have a place to drain into in there it would make things easier for you maintenance-wise, none of the other factors would cause any issues with its operation. They're basically like air conditioners that suck the moisture out as the air passes through them and drops the water into a small res or drain. This might be your best options as it's so high, it would also raise your temps by a couple of degrees if running it inside the tent. You could put it on a timer or controller that would kick in only when needed, e.g. higher than RH 60%.

GroErr said:

Not sure on the sizes out there as I haven't looked around for one for a long time. It's a relatively small area so a small one would be fine. Only issue with humidifiers is draining them so if you can find one that has like a tap/drain tube and have a place to drain into in there it would make things easier for you maintenance-wise, none of the other factors would cause any issues with its operation. They're basically like air conditioners that suck the moisture out as the air passes through them and drops the water into a small res or drain. This might be your best options as it's so high, it would also raise your temps by a couple of degrees if running it inside the tent. You could put it on a timer or controller that would kick in only when needed, e.g. higher than RH 60%.

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Some have a humidistat I assume?

TedeBoy said:

Some have a humidistat I assume?

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The higher end one's can but that could get expensive, depending on where you buy it. Craigslist might be a good option for something like this. I have one that I haven't had to use since I finished my flower room with a built-in one, if not there are separate humidistat's out there, you just have to make sure they can handle the start-up amperage. Humidifier's/Air Conditioners pull quite a high amp draw on start-up.

TedeBoy said:

Here's my current weather at 6:30 am.

Temp/RH
Outside: 62F/91rh (raining)
Garage where tent is: 68F/60rh
In 3x3x7 foot tent: 72F/69-77rh

My White Widow autoflowers are starting to flower now and I'm concerned that the RH is too high and I don't know what to do.

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If they're just starting to flower then you don't have much to worry about because there's nothing to get bud-rot yet. When you start having buds then you need to be concerned about mold. Speaking of which, I would recommend putting a hepa filter of some kind on the air intake of the tent to keep mold spores out. I haven't heard others mention the importance of filtering the air intake but it's an obvious way to keep out mold and dust. In fact, the best bet would be to have a hepa air purifier that has a UV bulb in it to kill pathogens even if they get past the filter.

BobCajun said:

If they're just starting to flower then you don't have much to worry about because there's nothing to get bud-rot yet. When you start having buds then you need to be concerned about mold. Speaking of which, I would recommend putting a hepa filter of some kind on the air intake of the tent to keep mold spores out. I haven't heard others mention the importance of filtering the air intake but it's an obvious way to keep out mold and dust. In fact, the best bet would be to have a hepa air purifier that has a UV bulb in it to kill pathogens even if they get past the filter.

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I do have the intake air filter with HVAC filters that include mold and spores.

I have 2 Sun Blaze T5HO fixtures. They are 2' x 4 bulbs.
I mounted them on the sides of the tent at a slight angle down and adjustable with ratchet straps. They are up near the LEC.
Hopefully they will burn off some humidity. They will add some heat which will trigger the exhaust to run more and hopefully pull more humidity out.
Plus more light can't hurt.
Hopefully this helps for now. It's extremely humid weather right now but won't last forever.

TedeBoy said:

I have 2 Sun Blaze T5HO fixtures. They are 2' x 4 bulbs.
I mounted them on the sides of the tent at a slight angle down and adjustable with ratchet straps. They are up near the LEC.
Hopefully they will burn off some humidity. They will add some heat which will trigger the exhaust to run more and hopefully pull more humidity out.
Plus more light can't hurt.
Hopefully this helps for now. It's extremely humid weather right now but won't last forever.

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Good option, you can use the heat, extra light won't hurt and it should drop your RH a bit. I think you mentioned you're running those Autos 24/0 so you shouldn't have to worry about lights-off RH.

GroErr said:

Good option, you can use the heat, extra light won't hurt and it should drop your RH a bit. I think you mentioned you're running those Autos 24/0 so you shouldn't have to worry about lights-off RH.

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Thanks GroErr.
Next grow I will grow photos. I'm thinking 2 in either 5 or 7 gallon containers scrogged.
This will give me floor space for a 30 pint dehumidifier.
I live near the coast so humidity will be an issue especially lights off.

add more light, HPS or MH work well at drying the air out... Bring temps up to 75-80 with more lighting and increase airflow in the tent.

TedeBoy said:

Thanks GroErr.
Next grow I will grow photos. I'm thinking 2 in either 5 or 7 gallon containers scrogged.
This will give me floor space for a 30 pint dehumidifier.
I live near the coast so humidity will be an issue especially lights off.

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Best grow I had in my little 2x2x4 tent was doing what you're doing. I needed temps up so I added 3 cfl's and 3 LED bulbs to my COBs. The mix in colours/spectrum and higher temps netted me about 6.5 zips as a bonus

if you dont have enoufh room in the tent for a snall dehumi then you could always get a bigger one and dehumidify the garage and increase air flow through the tent to drop rh.

I added the T5HO lights.
Warmer and drier in the tent.

TedeBoy said:

View attachment 3570610 View attachment 3570611 I added the T5HO lights.
Warmer and drier in the tent.

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Nice! That's probably your best option. Best yields I've had whether under LED's or CMH have been keeping the temps in the 78-80F range lights on and 68-70F lights off. What colour (kelvin) are those T5's?

GroErr said:

Nice! That's probably your best option. Best yields I've had whether under LED's or CMH have been keeping the temps in the 78-80F range lights on and 68-70F lights off. What colour (kelvin) are those T5's?

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Unfortunately they are 6500K. I can't afford to change them out right now. I was wondering if that is a problem?
I guess I should check prices. I'm assuming.

TedeBoy said:

Unfortunately they are 6500K. I can't afford to change them out right now. I was wondering if that is a problem?
I guess I should check prices. I'm assuming.

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Hey if it's not in the budget they'll do. Something warmer would be nice (3500-4000) but I don't see it being a problem, the LEC will be the main spectrum hitting them as it's more intense than the T5's and directly over them. Should keep a close eye on any effects though, slight changes can make big differences.

Holding pretty steady at 78F and 60% rh.
Exhaust fan turned to a lower speed. It now runs all the time it seems. I've got 2 fans stirring up the air in the tent.
Ambient rh is 63% so it looks like the T5 lights are helping to burn off some humidity.

TedeBoy said:

Holding pretty steady at 78F and 60% rh.
Exhaust fan turned to a lower speed. It now runs all the time it seems. I've got 2 fans stirring up the air in the tent.
Ambient rh is 63% so it looks like the T5 lights are helping to burn off some humidity.

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Looks just about right, a tad lower RH would be nice but if you don't have PM in your area you shouldn't have any issues. My area is covered in PM (outdoor) so it seeps in everywhere, if my RH is above 60% it can trigger PM on certain strains, particularly indica's. To combat it I run all my fans including incoming/exhaust 24/7, only thing that changes is adjusting the variable controllers up/down for both exhaust/incoming air depending on the season. Not a bad thing to have constant airflow and air exchange.

You'll have to think about a dehumidifier though if you start running photos. As soon as lights go out, RH rises quick, at 60% lights on you'll hit somewhere around 70% within 30 minutes of lights off. I have wireless temp/RH monitors that keep a weeks worth of data and can see temp/RH changes even when I just go into the room to water.