Drastic Temp & RH Swings In Greenhouse

[BakedARea]

Hey everyone. So my plants are outdoors in a cheap Harbor Frieght 6x6 greenhouse. It has been great to hide the plants from company that happens to swing by. The downside to this though is that it get very toasty inside if the doors and vents are closed up. Having to rely on my kids to open and close them reliably is a bit of an issue as well. When I saw toasty, I mean like 100°+ inside when it is only mid 70s outside. Then at night, it drops into the mid 50s. On top of that, the RH levels swing dramatically as well. From low 20% when it's hot in the greenhouse and then climbs into the 70s toward the end of the day and during the evenings.

How will these two things affect the quality of the buds? When growing outdoors without a greenhouse, temperature swings are not dramatic like except for your temp drops in the evening. Thankfully, the soil insulates the root system to protect them from temp swings. Not so much with a fabric pot is what I am thinking. Looking forward to reading your insights.

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• BakedARea
• Jul 29, 2019

 

[Ganjier]

The high temps will likely stunt growth somewhat and result in reduced bud density or fluffy buds but as long as the temps don't go much over 100 F you should be ok as long as the plants are watered. Not optimum temp conditions but you should be ok. Depending on the cultivars that you are growing, RH of 70% or higher could be ok for a sativa with airy buds but will likely cause botrytis or bud rot with indicas or indica heavy hybrids which will be detrimental once it starts.
My guess it that with the doors closed and sealed your RH is spiking to well over 70%, more likely in the 90% to 100% range at times.

To address this you will need to install some fans to extract the hot and moisture saturated air and pull in fresh air from outside of the greenhouse. It would also be good to install a small fan or two to keep air circulating through the plant canopies at all times. In other words, to manage the environment you'll need to set up your greenhouse in a very similar way to an indoor grow tent setup.
Another option would be to leave the top of the greenhouse as is to protect from rain but roll up the sides and end walls to allow adequate air movement. But then your plants would be visible to any visitors.

 

[BakedARea]

Yeah, we have been rolling up the front door and the back vent when we know nobody's coming over. Unfortunately, I want to keep my son's friends from seeing anything since they are still young*ish. Thankfully my son is completely aware and educated about it should someone end up seeing it. My guess is they would tall to their parents which would most likely result on some knocks on the door. Don't want to ruin his friendship because of ignorant parents you know.

I do have a fan hooked up in there running all the time. It is on the flooran pointing upward a little. Drawing some fresh air from beneath the greenhouse. I don't have anything venting out though, just the window vents. I can leave the back one down all the time since it faces the back fence. Could hook up another small fan pointing toward that window to push hot air out. That would help regulate the RH to match the outdoor RH. When it gets hot, it has dropped to below 30%. I think at one point, it hit low 20% and 110. Did not last long though. Had my daughter open up the door as soon as she told me. I'm getting a WiFi thermometer and hydrometer hooked up to at least give me a heads up when things are too hot. Be able to give advance notice to the kids to open it up. Thanks for the insight @Ganjier . Helped me formulate a better plan.

 

[Ganjier]

If you're able to keep the back rolled up it may be best to hang a cheap box type fan high up along the back wall where the air is warmest with the fan facing outward to extract the air. Then if it's not a problem, roll up the front door just high enough to allow fresh air to enter yet still low enough to shield the foliage from view. This would give you a cross flow fresh air current through the greenhouse.

 

[HugePeckerhead]

They have air conditioning that don't need windows either. With some tinkering I'm sure you can find a sweet spot to help drop the heatand humidity

 

[TurboBucket]

If it were me I'd leave that vent open for a few days and see what happens. 50 degree nights won't kill them by any means and would be far desirable to 100° days

 

[BakedARea]

I wanted to share what I ordered last week for remote monitoring via phone app or website. Very affordable setup too! It is WiFi based thermometer, hydrometer, and soil moisture meter. I can add up to 8 soil meters which I thought would be convenient in the future. I also registered to my nearest weather station (less than 1 mile away) so that I can track other factors throughout the year. I will also be able to track the temps in the tent and compare them with the outdoor temps. I'll be able to build a better picture of how one affects the other moving forward. Here are some pics for reference. Anybody else ever try the EcoWitt sensors?

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• BakedARea
• Aug 8, 2019

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• BakedARea
• Aug 8, 2019

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• BakedARea
• Aug 8, 2019

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• BakedARea
• Aug 8, 2019

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• BakedARea
• Aug 8, 2019

 

[Ganjier]

I've never used this system but it sure does have lots of cool features. Best of luck with getting those temps down and RH under control moving forward. Looks like you're on the right path.

 

[BakedARea]

I appreciate the support. I'll be adding a fan to the back vent tomorrow afternoon!

 

[Ganjier]

If you can get your max temps down to 90 F or less and RH down to a max of 60% or less this will be very beneficial. Best of luck and feel free to hit me up if you have any other questions or need some additional advice. I'll be happy to help if I can.

 

[BakedARea]

Definitely need to get a fan for the back vent. Climbed up to 100+° again. Got notification via email that the temps shot passed 100. That was a cool feature. Texted my kid, opened up the doors and temps regulated back down quickly. I don't like those sudden spikes I guess. Can't be fun for them. Getting the fan installed tonight if plans workout. Need to go buy a fan first...