Tips to keep greenhouse cool?

Trigobontree

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I have a new 4x6 panel greenhouse to keep my trees in to protect them from critters, wind, and my toddler. However I’m having trouble trying to keep it cool. I have a shade cloth covering the southern exposure side, and a vornando fan, however even with the vent and the door open (which doesn’t help keep the toddler out) it still feels really warm in there. Does anyone have any inexpensive tips for how to keep it cool? I’ve attached some pics (I took them this morning and its still cool outside so I don’t have the door or vent open yet).
 

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JackHammer

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I keep my tropicals in a 10x12 greenhouse and keep the door open at all times.
Do you have a thermometer?
I have a cheap thermometer in my greenhouse and have noticed that as long as I have the door open, it doesn't get too bad, maybe 105-110. I don't keep a lot of bonsai in there because I don't want to cook them on accident. I also keep some shard and cabbage in pots as my canaries. They are colder weather plants so if they start looking bad, I will know the upper limit. I would also not be upset if I lost them. They have been growing exceedingly well, despite the heat.
 

hinmo24t

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good luck. i thought that aside from tropicals it would be used for over the winter or getting a jump/extension out of growing seasons. where did you get that small hard panel setup?


thanks
 

Bonsai Nut

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Stake your shade cloth at least 12" away from your greenhouse panels. If you lay the shadecloth directly on your greenhouse, the majority of the radiant heat passes directly to your greenhouse panels.

Otherwise, you could consider spraying it with greenhouse whitewash to reflect the sun.
 

Leo in N E Illinois

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When commercial greenhouses are set up, they install huge fans. To keep a greenhouse cool on a 80 F day, you need to be able to exhaust the entire volume of the greenhouse at least once every 3 minutes to once a minute. On a hot day, you need to move a lot of air. As the temperature goes up, you need to move more air. On a 95 F day you would need a complete air change once a minute to keep the plants from getting hotter than air temperature.

You need to break out your calculator. Calculate the volume of the greenhouse. Then shop fans at a place like Greenhouse Mega Store. Look at the volume per minute values for the fans. ANother place to shop is Grainger.



Hobby size greenhouses are usually intended to keep plants warm in winter, and are usually empty for the summer, everything being put outside. They are not normally built with enough ventilation for summer time use. If you add ventilation, they can be used year round.

Swamp pad coolers are economical for cooling a greenhouse, if humidity is not too high during your warm spells. Swamp coolers work by forcing air through a fiber pad that has water dripping through the pad. The water evaporates, chilling the air as it evaporates. Works really well as long as the relative humidity is less than 90%. During very humid weather, the cooler will not work. Probably no problem in your state. In places like Louisiana swamp coolers are not as effective because of the high humidity outdoors. In the desert southwest they are very effective, though the amount of water required is somewhat scarce and expensive.

For protection against critters. Instead of a glazed greenhouse, a screenhouse might be a better option. Essentially replace all the glass with wire mesh. If your glass or plastic panels can be removed without damaging them or the frame. Consider removing panels and replacing them with wire mesh or window screen. Replace the glazing as weather cools in autumn. Or have 2 structures. A greenhouse to extend the seasons, and a screen house for summer time use.
 

Trigobontree

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I keep my tropicals in a 10x12 greenhouse and keep the door open at all times.
Do you have a thermometer?
I have a cheap thermometer in my greenhouse and have noticed that as long as I have the door open, it doesn't get too bad, maybe 105-110. I don't keep a lot of bonsai in there because I don't want to cook them on accident. I also keep some shard and cabbage in pots as my canaries. They are colder weather plants so if they start looking bad, I will know the upper limit. I would also not be upset if I lost them. They have been growing exceedingly well, despite the heat.
Ok, good to know your tropicals can survive the heat. I have tropicals in there now. I have a few native trees that I’m letting thicken in the ground for another year or so but otherwise all of my plants are sub-tropical.
 

bwaynef

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I rebuilt my greenhouse after it took a tumble during an unfortunately-timed unstaking right before a tropical storm blew through. I had to replace a few parts, but opted to put it on pavers and on a 4x4 base. That provided a 14" (4x4s are 3.5"x3.5") lift. That made the greenhouse immensely more useable at the time (late winter), but I wouldn't see all of its benefits until summer. The additional height made it easier for me to put trees on benches w/o them touching the sloping panels that make the roof. It also gave me more room to move around in there reaching the backs of the benches without bumping my head on those roof panels.

The part that's of interest to this thread though is that the heat that builds up goes to the roof. That means that with the extra height, the heat is further from the plants as well. Now I've got a split door and a vent in the roof, both of which I leave open. I also have a fan at the back of the greenhouse to move a bit of air as well as an exhaust fan on the door blowing out.

I've got a shade cloth over it as well. I've been trying to figure out a way to get the shade cloth lifted off the greenhouse as well. I can't wait 'til lumber prices come down.
 

Trigobontree

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good luck. i thought that aside from tropicals it would be used for over the winter or getting a jump/extension out of growing seasons. where did you get that small hard panel setup?


thanks
I tried just keeping them on the patio, but I live in a really wooded area. Lots of little animals. I’d go out in the morning to the soil scattered everywhere. And we live 30 mins from the coast, so we get the occasional tropical storm. I got it from Wayfair, they’re also on Amazon. It’s a palarm.
 

Trigobontree

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The swamp cooler is a good idea. I hadn’t thought of that. The panels don’t come out very easily once installed.
When commercial greenhouses are set up, they install huge fans. To keep a greenhouse cool on a 80 F day, you need to be able to exhaust the entire volume of the greenhouse at least once every 3 minutes to once a minute. On a hot day, you need to move a lot of air. As the temperature goes up, you need to move more air. On a 95 F day you would need a complete air change once a minute to keep the plants from getting hotter than air temperature.

You need to break out your calculator. Calculate the volume of the greenhouse. Then shop fans at a place like Greenhouse Mega Store. Look at the volume per minute values for the fans. ANother place to shop is Grainger.



Hobby size greenhouses are usually intended to keep plants warm in winter, and are usually empty for the summer, everything being put outside. They are not normally built with enough ventilation for summer time use. If you add ventilation, they can be used year round.

Swamp pad coolers are economical for cooling a greenhouse, if humidity is not too high during your warm spells. Swamp coolers work by forcing air through a fiber pad that has water dripping through the pad. The water evaporates, chilling the air as it evaporates. Works really well as long as the relative humidity is less than 90%. During very humid weather, the cooler will not work. Probably no problem in your state. In places like Louisiana swamp coolers are not as effective because of the high humidity outdoors. In the desert southwest they are very effective, though the amount of water required is somewhat scarce and expensive.

For protection against critters. Instead of a glazed greenhouse, a screenhouse might be a better option. Essentially replace all the glass with wire mesh. If your glass or plastic panels can be removed without damaging them or the frame. Consider removing panels and replacing them with wire mesh or window screen. Replace the glazing as weather cools in autumn. Or have 2 structures. A greenhouse to extend the seasons, and a screen house for summer time use.
 
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Wondering if you have both the base Param roof vent and the side louver option installed on your greenhouse?

I have both with auto openers, (not needed - but saves running hither and yon) and shade cloth and that seems to help a lot with keeping the temperature down

…. of course we are in the Puget Sound area. Nothing helped when it was 110F outside!

cheers
DSD sends
 

penumbra

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If you have the money and space, a cool cell evaporative greenhouse cooler is the way to go. The small portable units are useless in high humidity areas. But the wall type units are frickin amazing. There are probably plan available on build your own. I had a friend year back that built one for a 20 x 20 orchid greenhouse. He's gone now and so is his greenhouse.
 

Wires_Guy_wires

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Cheap white latex paint comes off of glass easily and reflects light and heat.

An old radiator and a pump attached to a kiddy pool might work too. Instead of heating, you can use it for cooling just as well.
 

sorce

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Take the roof off!

I ....take the..... top...offa...that...green....house...

Sorce
 

Trigobontree

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Wondering if you have both the base Param roof vent and the side louver option installed on your greenhouse?

I have both with auto openers, (not needed - but saves running hither and yon) and shade cloth and that seems to help a lot with keeping the temperature down

…. of course we are in the Puget Sound area. Nothing helped when it was 110F outside!

cheers
DSD sends
No side vent on this model, just the roof. I mentioned cutting out a side one to my fiancé (who spent all week installing it) and he gave me a look and said it would of been easier before he had put everything together. Have to wait a couple of days for the honey-do list to reset. He pretends to not care about the trees, but I caught him checking on them yesterday: I think he’s coming around.
 
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😎. I read somewhere in a Palram side louver review where someone actually post construction installed a louder vent. They mentioned it wasn’t all that hard, once they thought it though. Maybe you’ll have luck getting one once your SO gets more attached to the trees. 😉
cheers
DSD sends
 

hinmo24t

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No side vent on this model, just the roof. I mentioned cutting out a side one to my fiancé (who spent all week installing it) and he gave me a look and said it would of been easier before he had put everything together. Have to wait a couple of days for the honey-do list to reset. He pretends to not care about the trees, but I caught him checking on them yesterday: I think he’s coming around.
well played


i know the simsbury area well btw
 

penumbra

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An old radiator and a pump attached to a kiddy pool might work too. Instead of heating, you can use it for cooling just as well.
This reminds me of a guy I knew many years ago that needed a chiller for a 220 gallon reef tank. He pumped water through a copper coil that was buried under over 3 feet of earth to cool his tank. Apparently it is a lot cooler under a good soil depth. I know that caves around here are about 53 -56 degrees F.
 

QuantumSparky

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+1 for having the shade cloth not touching the greenhouse. As mentioned before, the black cloth will block light (and by extension, heat) by absorbing it. The problem with that is the fact that now you have a hot wrap cooking the air inside your greenhouse. Think of an electric stove heating up a pot, except upside down. If you have the shade cloth a foot or so off the panels, then all that heat the cloth absorbs will just radiate back into the environment while it blocks the extra sunlight from your greenhouse. It's the difference between wearing a black shirt in the sun, and having a black tent a few feet above you casting shade. I'd definitely prefer the second option
 

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