greenhouse Interior greenhouse shade cloth ...

I recently bought an 8'x16' greenhouse and have been battling temps. Their not horrible, but they get from 90-100 degrees during the day with an ambient temperature of 85-90 degrees outside which is still to high. I have a few exhaust fans but they arent getting it down to ambient temps so Im looking into other alternatives, either getting bigger fans or a evaporative cooler, etc, etc.
Anyway, I bought the shade cloth system that the company offers. The problem is, its an INTERIOR shade cloth system. It just dawned on me that since the shade cloth is on the interior... its probably not doing jack to reduce internal greenhouse temperatures!?? Would you say this is correct? So basically all Im doing is reducing the light getting to the plants.

I know shade cloths work, and many use them .. but thats in an effort to reduce temperatures, correct? Basically your sacrificing light exposure in an effort to reduce temperatures, and thats a fair trade... but if my shade cloth is inside, the sunlight is still hitting the polycarbonate roof, and therefore heating up the interior, the fact that a piece of material is reducing light exposure to the greenhouse interior isnt going to reduce temps if the roof is still getting blasted with sun... I wouldnt think??
Am I correct? The damn thing was like $250 too. Stupid. lol
Heres a pic of what Im talking about, I know its a bit hard to see ... but the material is hung inside the greenhouse, not on the outside, so again ... the suns still hitting the polycarbonate of the greenhouse itself. So I gotta think the shade cloth is doing nothing to reduce temps.

BTW ... the interior shade cloth does not fit as well as the picture shows ... in actuality it hangs down about 5-7" or so underneath the polycarbonate roof. Not that it really matters, either way the suns still hitting the exterior of the greenhouse.
If your temps are 85 why are you using a greenhouse? Also I have a greenhouse and I take the plastic off during spring/ summer and replace fall/winter
I use a 50% shade cloth over my greenhouse. If I remember correctly, it drops the daytime temp by about 7 degrees. I also have a evaporative cooler that will drop the temps another 10 degrees. Last year during our heatwave, ambient temps were consistently hitting 105 and I managed to hold around 90 degrees inside.
This is the cooler that I use.;ft_cooling_fans-ft_fogging_systems;ft_low_pressure_fogging_systems.html
I have the 30" oscillating fan, not a cheap solution but it works really well. I also have a brass solenoid that is connected to my main water line for the greenhouse. It is wired to my thermostat so when it hits 85 the solenoid opens and I get a good misting until the temps drop back down. The only issue is that I have hard water, so the calcium starts to build up on just about every surface. In the fall I have to go in and spray CLR on the polycarbonate to restore the clarity.
Nightshade said:
If your temps are 85 why are you using a greenhouse? Also I have a greenhouse and I take the plastic off during spring/ summer and replace fall/winter
Thanks for the input nightshade. Several very important reasons:

1) My nightime temps range from 38 deg to 48 deg right now in june and July ...and in a greenhouse I can run a heater at night to keep nighttime temps up. (I'm at 7,000 feet in the mountains - its Arizona so our Sun is STRONG but I'm in the mountains so our temps get low at night. the highest it will ever get will be 45-55 degrees at night in peak summer)

2) Since its Arizona still and our Sun is so strong in a greenhouse I can keep them going almost year round. I'm told the local greenhouses get to 80 degrees during the day in the middle of winter when the suns out...which it almost always is. The winter lows are around -10 at the worst...but only for a month...most of the winter we will be around 15-30 or 40 degrees even. Just gotta run a heater at night.

3) our wind is ridiculous and makes it very hard to grow vegetable crops without some sort of protection from the wind... which the greenhouse provides in addition to the reasons above. a side note my greenhouse is a permenant 8mm polycarbonate model. Theres no plastic to remove.

Ghost pepper- thanks for all your help in all my posts. Your shadecloth is an exterior one though...isn't it?

What I'm wondering is if an internal one will cool temperatures ...I don't think it will? I understand that an external one will because it keeps the Sun off the greenhouse. This internal one I have doesn't since its hung inside ... so really all I'm doing is reducing light..with no benefit on temps? At least that's what I'm speculating.

What are everyones thoughts on that? Do you agree?
Your best option is to vent out at the highest part of your greenhouse. This will create a sort of suction effect to pull the hot air up and out. Think about how your roof is vented on your house, it has vents on the lower outside and then a ridge vent. Same concept. Also, you can buy custom size shade cloth to fit your greenhouse for alot cheaper. Tie it down on the outside and your good to go.
I have ventilation in place, installed just as you say ... but its not enough. I may need to go to an evaporative cooler but Howard, if yours are fine in 106 degrees then I dont know what Im worrying about. With my current ventilation and no shade cloth the highest it ever gets is around 105. Most every day is around 95 -100.
I really appreciate everyones input. Howard, since your here in AZ with the intense sun Ild really like to pick your brain a little.
Your plants arent producing in those temps though are they??
Also... how many hours of direct sun are they getting??
OZ, I agree with your thoughts on the internal shade cloth not being effective. Sorry, I didn't realize that is what you were asking. I can tell you that the commercial greenhouses I have been in, use shade cloth internally, but they also play by a different set of rules. If I were you, I would purchase a shade cloth that could go on the outside.
No worries at all... I guess ill have to look into one ...this one cost me $250. Maybe ill see if I can return it
Yeah I would try to return it too. You can also check farmteks website. Sometimes they have special deals on pieces leftover from full rolls. You would have to put grommets in yourself but it would save you some money. Look around on their website or give them a call. They are real nice folks and have awesome customer service.
Again, oooz

Your problem of too high day temp and too low night temp has one simple solution :


Don't want to sound mean (really) - but stop throwing moneys at the problem and use solar máss to kill 2 birds with one stone.

Cheers Al

Ps:the interior shade cloth does what is made for... I makes SHADE, not lower the temps...

If you need to lower the energy that gets into the gh, than you need to shade outside of it.

Iiwy I'd shade outside and make a cutout in one or 2 of the top panels to increase ventilation (you mention you have winds)
Dont worry Al, no offense taken I appreciate the input. Solar mass is not a viable option, I do not have the space for the amount of 55 gallon durms it would take to make any difference. Even if I did it will not reduce the temperatures by 20-25 degrees during the day, nor will it increase the temperatures by 20-25 degrees at night.

According to all the solar mass guides, you need a MINIMUM of 2.5 gallons of water per sq foot of greenhouse space, 5 gallons of water per square foot is better still. That means I need a minimum of SIX 55 gallon drums full of water and more properly up to TWELVE 55 gallon drums if I really want to see any improvment. Ive researched solar mass in depth and even with that kind of water capacity its still not going to raise or lower the temps by a 20-25 degree range. Plus, as mentioned ... I dont have space for six 55 gallon barrells, much less twelve of them.
I agree with the interior shade cloth not lower temps, as mentioned above.
I took it down and temps are staying the same as with it, so Im going to just take it down and look into other options.
my plants get full sun in the morning for 3 hours and afternoon for the same.. indirect the rest of the time. The jalepenos are flowering right now since they are 3 weeks older, the others havent got there yet.
All the greenhouses around here just leave the front and rear doors wide open at all times during the day. Never feels that much hotter than outside temps. Also make sure your exhausts are blowing and pulling in the right direction. Blow on one end, suck on the other type of thing. Highest point etc etc...its all been said. Hope you get them temps down! 

Also, yes I still believe the shade system you bought will work fine! Not a waste of money in my eyes. Have you monitored the temps since installation?
Thanks everyone.
PG .... Ya Ive been tweaking and fiddling with it. I only have a front door, there is no rear door so that doesnt work with this greenhouse. I have three min/max thermometers in there and Ive been monitoring temps... the temps seemed to stay around the 90-100 degree mark with the shade cloth installed installed, I removed it yesterday and the temps were about the same 95-105 but it has been cooler outside the last few days. Ill have to watch it closely over the next couple days. If its only going to make a 5 degree difference Im just going to get rid of it. No point in reducing the light by close to half for only a 5 degree benefit in temps.
An evaporative cooler would be sweet. I could keep the temps 80-85 degrees while increasing humidity, plus I could get rid of the shade cloth all together and let the plants get full light (the polycarbonate panels are UV resistant so the plants still get some protection in the greenhouse).
I did already order two bigger exhaust fans though.
My current fans are 12" at 1100 CFM each, 2200 CFM total and arent quite keeping it as cool as Ild like.
The new fans are 16" at 2950 CFM each... for 5900 CFM total - almost three times as much.
Problem is Ild have to cut bigger holes in the greenhouse for the new fans, and if doesnt reduce temperatures to the same as ambient outside temps, I didnt do much good and I cut bigger holes in the greenhouse which I dont need if I go to an evaporative cooler. I could use those holes for automatic shutters that open up when the cooler turns on, but I dont need two 16" holes for that either.
Ill keep you all updated I just wasnt sure about the shade cloth doing any good for inside temps when its hung inside the greenhouse.
Tweaking begins!!  :)
Thanks again
Hey guys ... I just started a grow log in the GLOG section.
Will someone go post a response so I can finish posting pics? Theres a pic limit and apparently I can post more pics until someone replies.
Heres the log:
Oh btw ... the internal shade cloth DOES bring down temps. Even though its hung inside. I took it down yesterday and put it back up at noon today, got about a 10 degree drop within 20 minutes of it going up.
Im sure an external one would do better, but Im just going to put bigger exhaust fans in next week and call it good.