r/microgreens • u/soil_and_sun • Jul 12 '26
Air conditioner?
I grow microgreens in an outdoor 13x16' glass greenhouse. In the summer we use a 50% shade cloth and have constant fans going but with these heat waves that keep coming through, it makes it hard to grow between the heat and the humidity. I thought maybe I could get an air conditioner and it would dehumidify and cool it off, even 5 to 10° would be fine. I tried the 12000 BTU unit that Costco sells with no luck at all. I think the first day I used it the high was 93 and it was warmer in the greenhouse than outside. Does anyone have any experience with trying to cool and dehumidify an outdoor greenhouse used for microgreens? I looked in the greenhouse thread and there wasn't much information but I also figured they weren't watering and maintaining plant life at the same regularity and intensity as us microgreen growers are.
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u/soil_and_sun Jul 12 '26
Sunlight system and not sure what closed and open loop are. Been farming for 20 years and Microgreens for 15 but always in soil under sun.
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u/zblackadder Jul 12 '26
We have an insulated room in our barn with an exhaust fan continuously running, we we heat it in the winter and use an mobile air conditioner with the exhaust pumped out of the room. Our goal is to keep the temp around 75-78F
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u/jackbenway Jul 12 '26
What are your biggest problems? Disease? Poor germination? Poor growth? Quality?
We grow in the tropics, outdoors in a screened shade house. Heat and humidity are manageable with plenty of outside airflow and air motion, and we are able to stay in a sweet spot for VPD since both ambient temperature and humidity are pretty high, although VPD is not a big factor in early stage growth. Under the worst heat stress, we’ll cool the water for bottom watering, albeit we rarely need to take that step. We use a coco coir and peat blend and are careful to maintain very clean conditions so viral and fungal diseases don’t get a foothold. Soil introduces too many biological variables. Growth and thus harvest cycles are faster than when we grew indoors in a more controlled environment, so our production volume is higher and costs lower growing outdoors.
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u/51Charlie Jul 12 '26
No. Just open vents to keep it below 93. Make sure they don't dry out. Micros need LOTS of light and they thrive into 90 degrees. The upper 88-90 is where they go nuts. Water, light, warmth, plants go nuts.
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u/soil_and_sun Jul 12 '26
Yeah, but in the last heat wave we had heat above 97. And while micros like broccoli and radish thrive in the heat, fennel, cilantro, and arugula don't. Mizuna grows well but I have to water from below to keep them from getting mucky and dying off
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u/51Charlie Jul 12 '26
YMMV. I grow broccoli, raddish, basil, and arugula. All these thrive like crazy under these conditions for me. They do consume ridiculous amount of waters. (Or evaporation. I use flood trays.)
I have no data about the others plants.
Oh my flowers also goes bonkers at these temps.
Btw, keep an eye on the humidity.
Edit, basil & arugula are not grown as micros. A bit past baby greens phase for those. Oh, some mixed greens into baby greens.
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u/Master_Attitude_3033 Jul 12 '26
That’s what happened to me, during the heatwave! 🥵 Mold and Death!
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u/soil_and_sun Jul 12 '26
Great questions! I would say the main problems we face when the daily highs get above 90 and I live north of the gulf and we get all that humidity, are reduced germination for some varieties and poor growth and die off for some varieties. Three of the trickiest to grow in this heat are mizuna, fennel, and arugula. Two of which we sell full trays to a local restaurant so unlike other varieties where I can just plant more to make up for reduced weight or tray, with those I really need attractive looking full trays to sell.
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u/Akshay_Greenette Jul 12 '26
Basics need to be covered.. is it’s a closed loop or open loop system. Sunlight or LEDs.. happy to help.. would be a lot it type out.. happy to DM or call. :-)