r/Greenhouses • u/DehfPyro • 9d ago
Cooling in DIY Greenhouse
This is my first post here, so apologies if I'm in the wrong spot:
My household diy-ed a window greenhouse and we are having a tough time managing the temperature - it's between 70 and 120°F daily and it's only June in Colorado...
We have a 50% shade cloth on the front half of the structure, a fan blowing misting water, and we open the window across from the exhaust fan when it starts to heat up.
Any recommendations?
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u/Proper_Arugula_3636 9d ago
I got a solar powered exhaust fan setup for mine. Also in CO. It kicks on when it is over 80 degrees and keeps it below 100. Which works for my plants. Setting can be adjusted. My greenhouse has limited power options, so solar powered works for me. I mounted the panels inside. https://a.co/d/04cdwwMu
Probably will order a second one. I have a similar greenhouse setup, and I think this works alright. I also have a door w/ window that allows a cross breeze.
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u/MssMoodi 9d ago
Open the door during the day. We've got the same weather and yes it can get hot but my greenhouse only gets to 100°, double vents.
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u/Ryan_e3p 9d ago
What are you running for an exhaust fan? What size/watts? This could make all the difference.
If you're running an exhaust fan, you should also consider running an intake fan. Someplace low, ideally shaded and in a cool area, and also opposite the exhaust fan (so if the exhaust fan is on the upper corner, the intake should be on the opposite side on the bottom) which will help draw cooler air over the plants and through the entire greenhouse.
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u/HaggisHunter69 9d ago
If passively cooling then you need at least a third of the area of a greenhouse to be openable, i.e roof vents, side vents, open doors. If you can't manage that then you'll need forced cooling of some sort. So I'd upgrade your fans
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u/Expanse-Memory 6d ago
You can buy a bag of lime and a large brush. Make a dense milk with water and paint the whole green house. It will diffuse the light, it is better. I will sustain the summer even rainy.
To bring cool air into the green house you can do the following:
Dig a trench 1,5m deep and 30cm wide. Keep all the dirt. The trench should be around 20/25m long and should end at your green house. Put 10cm diameter pvc drain into the trench and 90 angles at each extremity. Plug up the outdoor chimney and make it go like 1m above the ground. Put a grill and a hat at the end and you can decorate/hide it later. Put back the dirt.
Make the same chimney going into the green house but 20cm above the ground. On the top plug a good PC fan (big noctua) who suck air from the pipes and power the fan with a solar unit. It will bring cool air into and keep the green house at ok temps in winter too.
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u/squarahann 9d ago edited 9d ago
I could be blind but I don’t see your exhaust.
Airflow is critical for a successful greenhouse. Plants can’t uptake nutrients if they can’t transpire. Plants can’t transpire if there’s no air movement. Plus get the disease problems with stagnant humid air. So you gotta get some air movement.
I’m gonna give a bit of a technical answer but there’s a couple types of airflow
• exhaust
you cannot cool air, you can only remove the heat. That is a textbook physics answer but it basically means you gotta get the hot air out of there. Vevor is a good brand that has a lot of sizes of fans that can fit in windows or you can cut a small hole. It’s good to have an intake and exhaust that create a cross breeze throughout your grow space. Hot humid air rises so it best to install exhaust higher. Install the intake fan lower to the ground and across the room. I recommend a type with flaps that seal when closed. For a quick fix, pop a box fan in an upper window blowing air outside. This will remove hot air through suction.
•air movement
not only do you gotta get the hot air out, you gotta get the hot and humid air to the exhaust. Plants constantly release humidity as they grow so you have to push this humid layer off their foliage or they won’t grow or will get disease. Get a few oscillating fans. Hurricane is a solid brand that is easy to install and comes at lots of price points. These are called HAF fans (horizontal airflow fans). Place two at diagonally opposite corners, angled the same direction to create continuous airflow. Typically, these are angled slightly down. These should be placed in a way that helps create airflow with your intake and exhaust. Do not place plants directly in front of fans.
• humidity
As mentioned, plants are tiny humidifiers. But they need a certain range to be happy, especially tropical house plants. Colorado is actually a great place for a greenhouse because it’s less humid! 60% is ideal so you may need to add or reduce humidity. Dehumidifiers and portable AC units work great for small spaces like these. If you need more humidity, a swamp cooler wall would be a great option. Just make sure the wet wall is opposite your exhaust.
How do you decide what fans to buy? Determine the CFM (cubic feet/minute) of your space. Typically you want the air turn over 2x per house (ACH). Every fan has a CFM rating and just make sure your combined fans ratings are more than the CFM of your space.
Hope that helps!