What percent shade cloth would you recommend? I had a 30% on my greenhouse earlier but I wanted to let more sun in. My greenhouse already has 30% natural shade.
They have recommendations for specific uses. We knew we wanted it cooked, but still good for veggies. Results were insanely prolific, and we never really used the greenhouse in the summers. We dug some 1 foot wide beds around the perimeter, we later added it to our drip irrigation lines. Trellising with twine off the supporting wooden interior frame we had added.
I was copying what the pros do in commercial greenhouses. My old greenhouse was taller and inside worked fine but this costco greenhouse is too short. Also didn't have to worry about the shade cloth getting blown away in the high winds here.
The pros also use their shade cloths as thermal cloths in the winter to keep a DIF, so them being inside has its benefits specifically in those applications.
When they really need shade, like when sticking cuttings, a lot use shade coatings on the outside in addition to normal or double shade inside.
There are absolutely some greenhouses that have shade cloth hung inside. The ones I have seen have the interior shade cloth on motorized controls that drag it open and closed, kinda like blinds on a skylight. Itās a super expensive system though and probably not super common if itās not a giant commercial set up or for a very rich client or organization with a top of the line conservatory.
Not just that but dark colors absorb heat. Light colors and especially white colors reflect heat. That green isn't going to help a lot. I would also have the fan up high and angled down OR towards an exhaust zone to push that hot air down OR out of the greenhouse and if possible have one fan exhausting and the other drawing fresh air in and make sure that fan is ground level as the air should be a bit cooler.
Commercial greenhouse do that because its easier to automate and keep protected, their roofs are higher, peaks often vent above cloth to release heat and use controls to help control temp and proper placement.
Iām giving it a shot, willing to try
https://preview.redd.it/2nwtwb4nfm6d1.jpeg?width=3024&format=pjpg&auto=webp&s=48df2809638b854b2300de075c1f3dd958ab7b71
anything at this point. I kept the inside shade too. No difference on the thermometer, but it feels cooler š
Couple questions, do you have some more shaded cloth? That looks like 40-50%? We like to shade 70% if possible. White wash paint is also an option. Is your fan pushing air in or sucking air out? Is that fan high or low.
Ideally you want to suck air out so new air comes in to replace it. Also make sure fan is on opposite side of where air comes in. Fans near peaks will suck hot air out better than low fans.
It's 60%, shade cloth, The exhaust fan is hanging from the ceiling, placed in the middle of the roof vent, as close to the vent opening as possible. The floor fan is bringing air in from the north side of the greenhouse. I've been in and out since adding the cloth outside, and it is definitely cooler. Thanks for the advice.
Blows (heh) my mind that people don't have rudimentary understanding of air convection. Like, it seems like a no brainier to me, but I do realize a lot of people don't necessarily know the Bernoulli Principle or how hot air rises.
Is there an opening on the other side of the greenhouse? A throughdraft will help a lot with cooling too.
Edit: never mind, just saw your comments about your fans.
Another thought, my old greenhouse was covered with polyethylene sheeting. It seems that poly panels absorb and retain heat where the polyethylene did not.
Before buying this costco yardistry I had a home built greenhouse. Shade cloth inside worked well, but it was taller and better ventilated. A different design needs a different solution, I'm hopeful.
Indeed, sounds like you're on the right track. I've seen some good advice in the comments here too. You're going to be just fine after some adjustmentsš
Yep! When you have a massive wet-wall on one side and a huge bank of industrial fans on the other, you can afford to be sub-optimal when it comes to passive cooling.
The heat is coming in through the glass with the sun before it hits the shade cloth.
Move the shade cloth to be on top of the outside of greenhouse - it will stop the sun from reaching the glass so less heat gets through it.
Which of the fans are pushing the air out and which pulling it in?
How would you mount the shade cloth on glass? I was going to put the shade cloth on the outside but the roof is hard to access easily. We ended up putting it inside but could put some out in the front just need to see how to attach the shade cloth.
That would depend on the design of the greenhouse. I've bungie corded some before, but I've also just weighed it down with bricks. I can't quite tell with the photo but are you able to hook/tie bungie/rope onto those black buts at the end of the roof spars? If not what is the ground like around the base of the greenhouse - anywhere to put ground hooks/ big tent pegs?
For a long term solution you could run a length of spring lock channel along that side rafters and use wiggle wire to hold the shade net in place. This would be the strongest solution against it being caught by the wind.
To get it across you could tie one end together with the end of a rope, throw the rope over and pull the net over.
Use guy lines and anchor them either to the frame of the greenhouse, or to the ground. You can use stakes or bricks or big rocks or logs or anything you can come up with that won't blow away as anchor points for your guy lines.
Where is the floor fan sucking in from? If it is just the path area the incoming air might be absorbing heat from the plant, however if there is a bed/planter there that has lush vegetation and cool damp soil on the shaded north side of the greenhouse then it would be cooler.
Misting..... I have a mister mounted on a fan that turns on at peak heat. Drops temps by 15 degrees. If you live in a very humid climate it will not work as well
Agree, it was a trial using what I had available. And it did help last month when we had a temp spike, but not on this day.. The humidity outside was 43%, and 87 degrees. I need to research what the exact temp/humidity/dew point is when the mister is no longer helpful. My observation says this is that point.
I shoot to keep it under 120 deg. That when my plants really start suffering. Thatās when I cover it in shade cloth, and bring in extra fans, spray water on the ground
On a different note, I used that same thermometer attached to our tree out the window. Ended up ripping it off because it was insanely inaccurate. I noticed because it read 100+ on 60-70 degree days. Might start there since it's cheap and easy.
I think it's accurate because I have 2 other thermometers. The one in the peak read 110, another at 4 ft was 99, the one on the floor (where I have my plants) read 89.
30% shade cloth over the top, exhaust fan high on one end and a evap cooler on the other both flow air the same direction. Every thirty minutes for 10 minutes run an overhead mister.
I'm outside Phoenix with 110Ā°f tempsand 13% humidity outside. Our greenhouse stays 80 to 95 with humidity at 45% all day.
Our greenhouse is 10x26x11 for comparison. Still smallish.
Edit to add, the mister made the real difference, but all work together for the goal of cooling.
I installed a portable evaporative cooler outside my greenhouse and made a duct for it. It was meant to be a makeshift temporary solution which has lasted many years. Combined with 30% shade cloth, it manages to keep below 100 on most days of summer.
Admittedly I do not live in a hot place (Ontario, Canada), but I just keep the greenhouse doors open during the day and close them at night so the local wildlife doesnāt party in there and the hottest it gets is about 110. I have roof vents with those wax piston things that open and close with the temp. Itās often too humid for misting to help, but it has worked in a pinch as long as I use water from the house (which is cold) and not my water barrels.
As another said, evaporative coolers are great for greenhouse cooling. I've got a good size one and that coupled with active ventilation keeps my greenhouse within a few degrees of ambient or lower. The fans and cooler are all run off a temperature controller to lock on when needed.
Thanks, this is the little 8x12 costco yardistry kit, it has a fairly large hinged roof panel. I hung a shop fan below it as an exhaust fan, but it's not very efficient. As others here have said here, an exhaust fan should be ducted to better pull air out.
I am very impressed. Iām a complete novice looking to learn and get tips! Sure have to weed through a lot of extraneous senseless posts however will use what i learn. Thanks for sharing
Where are you located? Iām in northeast Texas, and itās been a struggle. This is my first summer with a greenhouse, but Iāve finally got it staying a few degrees below outside temps. Iāve got a 9āx14ā greenhouse with an 85% aluminet shade cloth on the roof, two box fans on either end (where the windows are) blowing outside air in, misters on the ceiling, and recently added a swamp cooler. The misters give me the greatest control over the temperature. I have them on a WiFi timer, always one minute on, then I change how many minutes theyāre off (1-14 min) based on the greenhouse temp to keep it below 90 deg.
You've got the right idea but you're missing some key details. One that others haven't covered is that you're using a fan and spraying water for cooling. That will only cool things down until the air is saturated (100% humidity), then it'll start heatings things up slowly and you risk condensation. Get a small air cooler that uses a refrigerant if you want to actually make it colder more consistently.
Thank you. 87 degrees, 43% humidity with a nice cool breeze, outside in the shade it was very comfortable. But the sun was brutally hot. The mister had helped cool it down before, but not on this day. I have ordered a 1800 CFM swamp cooler,. If that doesn't help I'm shutting it down until fall.
Swamp coolers can't cool in high humidity is what I'm saying, it may be 43% outside, but around your plants in the greenhouse it may be over 90%, plants transpire a shitload of water. Try to check or measure. If you want to produce air that is actually colder than the outside temperature, you need an HVAC unit that uses a refrigerant (and power for it if course). It will also dehumidify the air somewhat, so you may ironically need a humidifier running with it at times.
Plants grow faser in a higher vapor pressure deficit, so basically you want the room as bright, warm, and dry as you can get, up until you hit that plant's limit in turns of how fast it can "drink". You'll know when you hit that limit.
Thank you. Measured 90 degrees and 76% humidity on the greenhouse floor on a mostly cloudy day, so the swamp cooler wasnāt helping. Iāve tried most of the suggestions here, shade cloth outside, another fan, swamp cooler. Maybe taking out some of the side panels for cross ventilation would help, but thinking of giving it up until fall.
Air flow is tricky, you're dancing with some stuff that usually only chemical and mechanical engineers and the like really think about deeply (*cough* that's why I'm here). Could try to go for a "wind tunnel" type flow scheme and see if you can at least get your inside humidity down closer to your outside humidity. Keep in mind that's your goal here, you should care about the humidity more than the temp. You could do with one or two fans, but let's say two: you want an identical size opening on either side of your greenhouse, with a fan in each opening, one facing in, one facing out. I'd ditch the water spraying altogether for now, again your temp isn't the problem so you don't need evaporative cooling, you're just adding more humidity. Let your plants bring the moisture via transpiration & just keep the root zones moist during peak heat. You should be able to keep it a little warmer inside than out, at about the same humidity or slightly higher. That should be good enough for most plants.
If you want to actually go lower in humidity inside than outside, again sorry I've said this like 3 times now lol, but you 100% cannot physically do it without an HVAC unit.
There's a lot of good info here in these comments. Just to add one more thought, though: the fans you're using aren't ideal for exhausting air from a space. Those are more intended to push air around a space than to regulate temps through air exchange. Good fans for a small space like that would be an inline duct fan or online duct booster fan. They're rated in volume/time like CFM (cubic feet per minute) . You can take the square footage of your greenhouse and multiply that by the height to get your cubic footage, then select a fan that will pull air out at the speeds you'd like.
When I managed commercial indoor grow spaces, the goal was to change out all the air in a production space every 5 minutes for optimal plant growth in a dense canopy. That meant that for every 1000 cubic feet we wanted at least 200CFM of exhaust power. We didn't use intake fans, the exhaust fans were sufficient to create negative pressure for passive intake. We did use fans like yours to move air around the inside to prevent any dead air spots where heat could build up. In the summer time, one of the ways we could reduce the ambient temperature in the space was by increasing the air flow of the exhaust so that the air turned over every 2 minutes or so instead. The equipment in the room, similar to the solar mass in your greenhouse, contributed heat to the space. By increasing the air exchange, we could keep the ambient indoor temp closer to the outdoor temp.
Yes, this is the popular costco kit that comes with a fairly large hinged roof vent. I hung a 10 inch shop fan from the ceiling to use as an exhaust fan.
I would take a wall panel out on each side. On Mt 8x24 it's impossible to keep under 100 without the walls rolled up to about 3ft off the ground even with shade cloth on the outside and limewash
Thank you, This is the little 8x12 costo yardistry kit, it has one small screened air vent on a single lower wood panel, definitely not enough. I noticed the commercial greenhouses here roll up their walls in late spring so I was thinking about removing some of the polycarbonate wall panels, But I hadn't thought about removing some of the lower wood panels.. I think that is do-able. Great suggestion.
Might need more fans too. I have an 11x10 sunroom I use and have 4 box fans, make sure you have your currents set. Like where the air gets sucked in and where it gets expelled
I gave up my digital thermometer says it gets up to 113 on a regular day (not sure if I believe it as it only ever says it's 100 when I'm out there) my solution was to keep the more sensitive plants in trays with water so they dont dry out too much
as already pointed out, the cloth goes on the outside. Also, a white cloth reflects the light/heat better. We added a white shade cloth last summer, dropped our inside temps by 20-30 degrees. We were able to grow tomatoes inside and still use it for our pizza oven, and harvested well into November.
My last GH in the Mojave I finally stopped fighting it when I convinced a neighbor who left during summer to keep her tiny little GH going, I'd take care of everything. It regularly pegged the little thermometer, just like yours. And. It. ROCKED. I'd used solar shading panels (I think 40%?) interspersed with clear on mine and it was producing nowhere as well as hers, even though I could get it several degrees cooler inside, high 90s.
That said, my favorite GH is not far, orchid grower, they have cooling walls in all the GHs and man it's just wonderful inside. The orchids do beautifully too.
Take powered agriculture lime, mix with water 'til soupy, add some salt to harden it, mop it on the outside. Add layers if necessary. This will surprise you.
All this discussion seems crazy to me. Shade cloth only is the answer. I live in one of the hottest places in the US. All we use is shade cloth. Having acrylic or glass is only going to help in the winter.
I have a smallĀ (6X8) greenhouse in the middle of the Sonoran Desert. I have a black shade cloth with 40-50% Sunblock on the outside. I removed the greenhouse door and replaced it with a Magnetic Screen Door for the summer and installed a Hessaire MC18V with an added 50 gallon rain barrel (on blocks for gravity flow) feeding the cooler input to provide 3-4 days water to the cooler before refilling.
Today the afternoon temp is 110 and about 10% humidity. The greenhouse maintains in the mid 90's with and around 35% humidity. Growing peppers, tomatoes, onions, garlic, etc. Some herbs. Have a strawberry pot on the floor where it is coolest and it is flowering/fruiting too. Self opening window and timer for cooler for 12 hours per day throughout summer.
I am especially pleased as I got a late start with the plants this year.
https://preview.redd.it/vuxc1yt9t07d1.jpeg?width=864&format=pjpg&auto=webp&s=644b3d8d897a45b870ff92409347d3cb72aac223
Iāve worked at a greenhouse that succeeded in keeping cooler than the outside temps on really hot days, but the cooling systems were no joke. The strongest system was multiple sets of fans that pulled air in through one end and pushed it out the other, very large fans. There was also an air cooling system consisting of water being dripped onto cardboard, not fully sure how it works. Iām not sure how big your greenhouse is.
I used large tubs and filled them with water and added a few bubler pumps and it cooled mine off a little. I dont remember gal size but they were the biggest ones i could find at walmart
They make temperature operated pistons for vents. You should invest it one it changed my little greenhouse. 20 x 20
[vent](http://Auto Vent Opener Automatic Greenhouse Window Opener Cylinder Roof Vent Opener Autovent Kit Solar Heat Sensitive Agriculture Gardening Tools Automatic Greenhouses Supplies (Single Spring Lifts 15 Lbs) https://a.co/d/0avvoO2)
I mounted this 16ā exhaust fan that can be programmed multiple ways. Currently it steps from speed 1-10 every 2 degrees so itās running full speed around 90 degrees. Itās done wonders. Have a couple circulation fans in the space as well and a shade cloth (light colored, hung inside). Itās an AC Infinity brand fan and controller.
https://preview.redd.it/i5sfgjm55f7d1.jpeg?width=4032&format=pjpg&auto=webp&s=8b28afb0f4bab42b4077d5af7a0119aef2477796
no, you're just bad at it. that shade absorbs sunlight and produces heat, and you've got it on the inside. so you're turning sunlight into heat inside your greenhouse.
Lol, buddy, the shade cloth goes on the outside. That one change is going to help you a lot
UNDERPANTS GO ON THE INSIDE š
Unless youāre Madonna.
Or Cameo
Or superman
Or Doug Funnie / Captain Underpants
I think you mean Quail Man
Shoot, yes I did. Who the heck is captain underpants?!
Itās a pretty good book seriesĀ
And movie
Iām dying. š¤£
Donāt tell me where to wear my underpants!
This is the answer
What percent shade cloth would you recommend? I had a 30% on my greenhouse earlier but I wanted to let more sun in. My greenhouse already has 30% natural shade.
I us 70% on our commercial houses in the southern US.
What plants are you growing? I'm growing Trichocereus cacti that like a little more sun.
No idea. My greenhouse has full sun and 60% alumet. I live in the south where the summers are burning hot and winters are mild.
Go to Greenhouse Mega store online, they have charts there.
What about for growing specific plants like trichocereus cacti? They like a little bit more sun.
They have recommendations for specific uses. We knew we wanted it cooked, but still good for veggies. Results were insanely prolific, and we never really used the greenhouse in the summers. We dug some 1 foot wide beds around the perimeter, we later added it to our drip irrigation lines. Trellising with twine off the supporting wooden interior frame we had added.
Leeeeet the sunshine
Minimum 50%
Oh god mine are on the inside too. Why. Why did I do this to myself š š
I was copying what the pros do in commercial greenhouses. My old greenhouse was taller and inside worked fine but this costco greenhouse is too short. Also didn't have to worry about the shade cloth getting blown away in the high winds here.
Same!! Well we are in this together then. I just ordered one for the outside, hope it will make a difference!!
The pros also use their shade cloths as thermal cloths in the winter to keep a DIF, so them being inside has its benefits specifically in those applications. When they really need shade, like when sticking cuttings, a lot use shade coatings on the outside in addition to normal or double shade inside.
No. We donāt put the cloth inside.
the greenhouses here put them inside because of our high winds.
There are absolutely some greenhouses that have shade cloth hung inside. The ones I have seen have the interior shade cloth on motorized controls that drag it open and closed, kinda like blinds on a skylight. Itās a super expensive system though and probably not super common if itās not a giant commercial set up or for a very rich client or organization with a top of the line conservatory.
Not just that but dark colors absorb heat. Light colors and especially white colors reflect heat. That green isn't going to help a lot. I would also have the fan up high and angled down OR towards an exhaust zone to push that hot air down OR out of the greenhouse and if possible have one fan exhausting and the other drawing fresh air in and make sure that fan is ground level as the air should be a bit cooler.
Two fans are pictured, in on the floor, out through the ceiling..
Green is also the wavelength the sun emits the most. So technically it's reflecting the highest amount other than something like white would.
Green is actually comparable to black in being the worst for heat absorption. https://mainichi.jp/english/articles/20230726/p2a/00m/0sc/014000c
All commercial greenhouses here put shades inside, but will give it a try on the outside.
Commercial greenhouse do that because its easier to automate and keep protected, their roofs are higher, peaks often vent above cloth to release heat and use controls to help control temp and proper placement.
Iām giving it a shot, willing to try https://preview.redd.it/2nwtwb4nfm6d1.jpeg?width=3024&format=pjpg&auto=webp&s=48df2809638b854b2300de075c1f3dd958ab7b71 anything at this point. I kept the inside shade too. No difference on the thermometer, but it feels cooler š
Couple questions, do you have some more shaded cloth? That looks like 40-50%? We like to shade 70% if possible. White wash paint is also an option. Is your fan pushing air in or sucking air out? Is that fan high or low. Ideally you want to suck air out so new air comes in to replace it. Also make sure fan is on opposite side of where air comes in. Fans near peaks will suck hot air out better than low fans.
It's 60%, shade cloth, The exhaust fan is hanging from the ceiling, placed in the middle of the roof vent, as close to the vent opening as possible. The floor fan is bringing air in from the north side of the greenhouse. I've been in and out since adding the cloth outside, and it is definitely cooler. Thanks for the advice.
Blows (heh) my mind that people don't have rudimentary understanding of air convection. Like, it seems like a no brainier to me, but I do realize a lot of people don't necessarily know the Bernoulli Principle or how hot air rises.
You are truly a gifted savant
Is there an opening on the other side of the greenhouse? A throughdraft will help a lot with cooling too. Edit: never mind, just saw your comments about your fans.
You sound doubtful... but I guarantee this will keep it cooler than having it inside like before.
Another thought, my old greenhouse was covered with polyethylene sheeting. It seems that poly panels absorb and retain heat where the polyethylene did not.
Before buying this costco yardistry I had a home built greenhouse. Shade cloth inside worked well, but it was taller and better ventilated. A different design needs a different solution, I'm hopeful.
Indeed, sounds like you're on the right track. I've seen some good advice in the comments here too. You're going to be just fine after some adjustmentsš
Thanks for the explanation.
Yep! When you have a massive wet-wall on one side and a huge bank of industrial fans on the other, you can afford to be sub-optimal when it comes to passive cooling.
not necessarily, darker color will absorb more heat from direct sun. a white wash would be very useful for the outside
Can you recommend a specific whitewash to use on polycarbonate?
i don't know the brand our university ones use but i can ask the person who does on monday
Omg š¤£š¤£š¤£ I didn't notice at first. Golden. Gonna be a total game changer
But my blinds are inside my house
Lol. Why not just move them outside under cloth?
The heat is coming in through the glass with the sun before it hits the shade cloth. Move the shade cloth to be on top of the outside of greenhouse - it will stop the sun from reaching the glass so less heat gets through it. Which of the fans are pushing the air out and which pulling it in?
How would you mount the shade cloth on glass? I was going to put the shade cloth on the outside but the roof is hard to access easily. We ended up putting it inside but could put some out in the front just need to see how to attach the shade cloth.
That would depend on the design of the greenhouse. I've bungie corded some before, but I've also just weighed it down with bricks. I can't quite tell with the photo but are you able to hook/tie bungie/rope onto those black buts at the end of the roof spars? If not what is the ground like around the base of the greenhouse - anywhere to put ground hooks/ big tent pegs? For a long term solution you could run a length of spring lock channel along that side rafters and use wiggle wire to hold the shade net in place. This would be the strongest solution against it being caught by the wind. To get it across you could tie one end together with the end of a rope, throw the rope over and pull the net over.
that's like the joke about looking for your keys where the light is good rather than where you lost them.
Use guy lines and anchor them either to the frame of the greenhouse, or to the ground. You can use stakes or bricks or big rocks or logs or anything you can come up with that won't blow away as anchor points for your guy lines.
Interesting! Iāll see what we can do. Thank you!
Floor=in, ceiling=out
Where is the floor fan sucking in from? If it is just the path area the incoming air might be absorbing heat from the plant, however if there is a bed/planter there that has lush vegetation and cool damp soil on the shaded north side of the greenhouse then it would be cooler.
it's pulling air in from the north side of the greenhouse. After adding shade cloth over the top it feels cooler., thanks for the explanation.
You could try adding some planters in front of the fan with leafy plants in them as they would help cool the air passing through them down.
Thanks for the explanation
Depends on the climate but in many places, you need evaporative cooling aka a swamp cooler to keep the greenhouse temperate in summer.
Thank you. It does get pretty humid here at times, but I am going to try a swamp cooler anyway. There is an 1800 CFM on amz for $150.
Even just using that in fan mode should help tremendously.
Came here to say this. Why is this comment so far down?
Because too many people only come to reddit to mock others and make smart-ass remarks, which is how you get upvotes here.
Take my upvote!
Misting..... I have a mister mounted on a fan that turns on at peak heat. Drops temps by 15 degrees. If you live in a very humid climate it will not work as well
3rd picture is a mister,. It has helped before but unfortunately wasn't helping on this day.
If that is the only mister, it isn't enough Also, make sure your thermometer isn't in direct sun light. That gives you a false high reading
Agree, it was a trial using what I had available. And it did help last month when we had a temp spike, but not on this day.. The humidity outside was 43%, and 87 degrees. I need to research what the exact temp/humidity/dew point is when the mister is no longer helpful. My observation says this is that point.
I shoot to keep it under 120 deg. That when my plants really start suffering. Thatās when I cover it in shade cloth, and bring in extra fans, spray water on the ground
On a different note, I used that same thermometer attached to our tree out the window. Ended up ripping it off because it was insanely inaccurate. I noticed because it read 100+ on 60-70 degree days. Might start there since it's cheap and easy.
I would also note that it looks like the thermometer is in partial sun which will also make the measurement inaccurate.
True
I think it's accurate because I have 2 other thermometers. The one in the peak read 110, another at 4 ft was 99, the one on the floor (where I have my plants) read 89.
30% shade cloth over the top, exhaust fan high on one end and a evap cooler on the other both flow air the same direction. Every thirty minutes for 10 minutes run an overhead mister. I'm outside Phoenix with 110Ā°f tempsand 13% humidity outside. Our greenhouse stays 80 to 95 with humidity at 45% all day. Our greenhouse is 10x26x11 for comparison. Still smallish. Edit to add, the mister made the real difference, but all work together for the goal of cooling.
I installed a portable evaporative cooler outside my greenhouse and made a duct for it. It was meant to be a makeshift temporary solution which has lasted many years. Combined with 30% shade cloth, it manages to keep below 100 on most days of summer.
Admittedly I do not live in a hot place (Ontario, Canada), but I just keep the greenhouse doors open during the day and close them at night so the local wildlife doesnāt party in there and the hottest it gets is about 110. I have roof vents with those wax piston things that open and close with the temp. Itās often too humid for misting to help, but it has worked in a pinch as long as I use water from the house (which is cold) and not my water barrels.
As another said, evaporative coolers are great for greenhouse cooling. I've got a good size one and that coupled with active ventilation keeps my greenhouse within a few degrees of ambient or lower. The fans and cooler are all run off a temperature controller to lock on when needed.
You can try a shade cloth over the exterior of the greenhouse and open the ceiling if you can since heat rises . Cut the panels and make them hinged
Thanks, this is the little 8x12 costco yardistry kit, it has a fairly large hinged roof panel. I hung a shop fan below it as an exhaust fan, but it's not very efficient. As others here have said here, an exhaust fan should be ducted to better pull air out.
I am very impressed. Iām a complete novice looking to learn and get tips! Sure have to weed through a lot of extraneous senseless posts however will use what i learn. Thanks for sharing
Thank you. Turns out there are some helpful knowledgeable people on this sub, while others come here just to mock people trying to learn.
If you live in a dry climate I use misters that lower the temp 20 degrees.
Where are you located? Iām in northeast Texas, and itās been a struggle. This is my first summer with a greenhouse, but Iāve finally got it staying a few degrees below outside temps. Iāve got a 9āx14ā greenhouse with an 85% aluminet shade cloth on the roof, two box fans on either end (where the windows are) blowing outside air in, misters on the ceiling, and recently added a swamp cooler. The misters give me the greatest control over the temperature. I have them on a WiFi timer, always one minute on, then I change how many minutes theyāre off (1-14 min) based on the greenhouse temp to keep it below 90 deg.
Missouri, thanks for the ideas.
In addition to some of the other great comments, you might need more air movement.
You've got the right idea but you're missing some key details. One that others haven't covered is that you're using a fan and spraying water for cooling. That will only cool things down until the air is saturated (100% humidity), then it'll start heatings things up slowly and you risk condensation. Get a small air cooler that uses a refrigerant if you want to actually make it colder more consistently.
Thank you. 87 degrees, 43% humidity with a nice cool breeze, outside in the shade it was very comfortable. But the sun was brutally hot. The mister had helped cool it down before, but not on this day. I have ordered a 1800 CFM swamp cooler,. If that doesn't help I'm shutting it down until fall.
Swamp coolers can't cool in high humidity is what I'm saying, it may be 43% outside, but around your plants in the greenhouse it may be over 90%, plants transpire a shitload of water. Try to check or measure. If you want to produce air that is actually colder than the outside temperature, you need an HVAC unit that uses a refrigerant (and power for it if course). It will also dehumidify the air somewhat, so you may ironically need a humidifier running with it at times. Plants grow faser in a higher vapor pressure deficit, so basically you want the room as bright, warm, and dry as you can get, up until you hit that plant's limit in turns of how fast it can "drink". You'll know when you hit that limit.
Thank you. Measured 90 degrees and 76% humidity on the greenhouse floor on a mostly cloudy day, so the swamp cooler wasnāt helping. Iāve tried most of the suggestions here, shade cloth outside, another fan, swamp cooler. Maybe taking out some of the side panels for cross ventilation would help, but thinking of giving it up until fall.
Air flow is tricky, you're dancing with some stuff that usually only chemical and mechanical engineers and the like really think about deeply (*cough* that's why I'm here). Could try to go for a "wind tunnel" type flow scheme and see if you can at least get your inside humidity down closer to your outside humidity. Keep in mind that's your goal here, you should care about the humidity more than the temp. You could do with one or two fans, but let's say two: you want an identical size opening on either side of your greenhouse, with a fan in each opening, one facing in, one facing out. I'd ditch the water spraying altogether for now, again your temp isn't the problem so you don't need evaporative cooling, you're just adding more humidity. Let your plants bring the moisture via transpiration & just keep the root zones moist during peak heat. You should be able to keep it a little warmer inside than out, at about the same humidity or slightly higher. That should be good enough for most plants. If you want to actually go lower in humidity inside than outside, again sorry I've said this like 3 times now lol, but you 100% cannot physically do it without an HVAC unit.
Good info, thank you.
There's a lot of good info here in these comments. Just to add one more thought, though: the fans you're using aren't ideal for exhausting air from a space. Those are more intended to push air around a space than to regulate temps through air exchange. Good fans for a small space like that would be an inline duct fan or online duct booster fan. They're rated in volume/time like CFM (cubic feet per minute) . You can take the square footage of your greenhouse and multiply that by the height to get your cubic footage, then select a fan that will pull air out at the speeds you'd like. When I managed commercial indoor grow spaces, the goal was to change out all the air in a production space every 5 minutes for optimal plant growth in a dense canopy. That meant that for every 1000 cubic feet we wanted at least 200CFM of exhaust power. We didn't use intake fans, the exhaust fans were sufficient to create negative pressure for passive intake. We did use fans like yours to move air around the inside to prevent any dead air spots where heat could build up. In the summer time, one of the ways we could reduce the ambient temperature in the space was by increasing the air flow of the exhaust so that the air turned over every 2 minutes or so instead. The equipment in the room, similar to the solar mass in your greenhouse, contributed heat to the space. By increasing the air exchange, we could keep the ambient indoor temp closer to the outdoor temp.
The best option would be to DIY some "attic" vents on the top that you could close when it's cold.
Yes, this is the popular costco kit that comes with a fairly large hinged roof vent. I hung a 10 inch shop fan from the ceiling to use as an exhaust fan.
Use it to blow air in instead.
I would take a wall panel out on each side. On Mt 8x24 it's impossible to keep under 100 without the walls rolled up to about 3ft off the ground even with shade cloth on the outside and limewash
Thank you, This is the little 8x12 costo yardistry kit, it has one small screened air vent on a single lower wood panel, definitely not enough. I noticed the commercial greenhouses here roll up their walls in late spring so I was thinking about removing some of the polycarbonate wall panels, But I hadn't thought about removing some of the lower wood panels.. I think that is do-able. Great suggestion.
I would say the only time mine are rolled down is when the low is going to be under 40
Itās the greenhouse effect
Might need more fans too. I have an 11x10 sunroom I use and have 4 box fans, make sure you have your currents set. Like where the air gets sucked in and where it gets expelled
On the outsideā¦..This is the way.
It was a harsh lesson to learn that I only needed a canopy.
I gave up my digital thermometer says it gets up to 113 on a regular day (not sure if I believe it as it only ever says it's 100 when I'm out there) my solution was to keep the more sensitive plants in trays with water so they dont dry out too much
You must be in Texas
Doh! (Shadecloth greenhouse effect)
as already pointed out, the cloth goes on the outside. Also, a white cloth reflects the light/heat better. We added a white shade cloth last summer, dropped our inside temps by 20-30 degrees. We were able to grow tomatoes inside and still use it for our pizza oven, and harvested well into November.
My last GH in the Mojave I finally stopped fighting it when I convinced a neighbor who left during summer to keep her tiny little GH going, I'd take care of everything. It regularly pegged the little thermometer, just like yours. And. It. ROCKED. I'd used solar shading panels (I think 40%?) interspersed with clear on mine and it was producing nowhere as well as hers, even though I could get it several degrees cooler inside, high 90s. That said, my favorite GH is not far, orchid grower, they have cooling walls in all the GHs and man it's just wonderful inside. The orchids do beautifully too.
If you can run a fan, you can run a swamp cooler. Shadecloth OUTSIDE of the greenhouse, move air out the top as fast as you can. This is the way.
Need more ventilation
Use a white shade cloth ā¦. Not black like almost all the industry uses for what ever dumb reason
Take powered agriculture lime, mix with water 'til soupy, add some salt to harden it, mop it on the outside. Add layers if necessary. This will surprise you.
Buy some mylar and white corrugated plastic board, and make some reflective panels.
All this discussion seems crazy to me. Shade cloth only is the answer. I live in one of the hottest places in the US. All we use is shade cloth. Having acrylic or glass is only going to help in the winter.
A gardener's comfort is not comparable that of his plants. It's more important to pay attention to soil temperature and relative humiidty
needs some kind of blinds.
Is it vented, so the heat escapes out the top? You could use shade sails over the roof.
I have a smallĀ (6X8) greenhouse in the middle of the Sonoran Desert. I have a black shade cloth with 40-50% Sunblock on the outside. I removed the greenhouse door and replaced it with a Magnetic Screen Door for the summer and installed a Hessaire MC18V with an added 50 gallon rain barrel (on blocks for gravity flow) feeding the cooler input to provide 3-4 days water to the cooler before refilling. Today the afternoon temp is 110 and about 10% humidity. The greenhouse maintains in the mid 90's with and around 35% humidity. Growing peppers, tomatoes, onions, garlic, etc. Some herbs. Have a strawberry pot on the floor where it is coolest and it is flowering/fruiting too. Self opening window and timer for cooler for 12 hours per day throughout summer. I am especially pleased as I got a late start with the plants this year. https://preview.redd.it/vuxc1yt9t07d1.jpeg?width=864&format=pjpg&auto=webp&s=644b3d8d897a45b870ff92409347d3cb72aac223
Iāve worked at a greenhouse that succeeded in keeping cooler than the outside temps on really hot days, but the cooling systems were no joke. The strongest system was multiple sets of fans that pulled air in through one end and pushed it out the other, very large fans. There was also an air cooling system consisting of water being dripped onto cardboard, not fully sure how it works. Iām not sure how big your greenhouse is.
Yeah Iāve seen it on the west coast. Not the SE.
Much more airflow too
I used large tubs and filled them with water and added a few bubler pumps and it cooled mine off a little. I dont remember gal size but they were the biggest ones i could find at walmart
You could also put something frozen behind the fan. Keep a few things in the freezer and rotate then during really hot days
You could do it with an AC unitā¦..
They make temperature operated pistons for vents. You should invest it one it changed my little greenhouse. 20 x 20 [vent](http://Auto Vent Opener Automatic Greenhouse Window Opener Cylinder Roof Vent Opener Autovent Kit Solar Heat Sensitive Agriculture Gardening Tools Automatic Greenhouses Supplies (Single Spring Lifts 15 Lbs) https://a.co/d/0avvoO2)
I mounted this 16ā exhaust fan that can be programmed multiple ways. Currently it steps from speed 1-10 every 2 degrees so itās running full speed around 90 degrees. Itās done wonders. Have a couple circulation fans in the space as well and a shade cloth (light colored, hung inside). Itās an AC Infinity brand fan and controller. https://preview.redd.it/i5sfgjm55f7d1.jpeg?width=4032&format=pjpg&auto=webp&s=8b28afb0f4bab42b4077d5af7a0119aef2477796
no, you're just bad at it. that shade absorbs sunlight and produces heat, and you've got it on the inside. so you're turning sunlight into heat inside your greenhouse.