How do u cool a greenhouse in summer?

Hi, I have a poly greenhouse 20x20. The temps are already getting too hot for flower. I'm in light dep and having a horrible time and it's only going to get worse. How can I cool the temp down in there?? I have a shade cover and vents with fans.

roll up the sides & open the ends....

Build a wet wall.
TMB-

I have a 30x50 with a 16 foot peak .. I have 5 foot roll up sides, 8 x8 doors front and back a 4x8 screened opening above the west end door ( where 95% of our spring and summer winds come from) and a 48" exhaust fan above the opposite end doors.
I'm able to keep within 3-5 degrees of the outside temperature.
Sometimes is there is little or no breeze I'll set up a sprinkler outside the west end doors and let the big exhaust fan suck in the cooler air.

WOW thank y'all very much for the help and advice. I just got the alert I had posts. I really appreciate yall's help.

treemansbuds said:

Build a wet wall.
TMB-

Click to expand...

This is what we have in the greenhouse at my ag school. Max temp is usually around 85.

I got 2 big fans and move 14000 cu ft of air a minute thru my greenhouse and it stays the same temp as outside with no issues rule of thumb is w x h x l in cu ft you need the same amount of air moving thru greenhouse to be effective to your need for temp control

Fadedlady said:

Hi, I have a poly greenhouse 20x20. The temps are already getting too hot for flower. I'm in light dep and having a horrible time and it's only going to get worse. How can I cool the temp down in there?? I have a shade cover and vents with fans.

Click to expand...

If you get a black screen and put it on the outside on the roof it accumulates heat and releases it outside the greenhouse. I also have fans for really hot days but I have 2 screens for airflow in the walls that help alot.