Last year I put up a 48' x 20' hoop greenhouse , double skinned and inflated. It was on my vacation from work (I worked in Saudi Arabia). I left a temperature recorder in there for a year and picked it up a few weeks ago. During summer it got to like 135F regularly.
I have fans and louvers on thermostats but didn't help much. So I just fitted misters in line with the louvers, also on thermostats. This has helped a little but Im still hitting 120F and the hottest part of the year is still to come.
So shade cloth I gather is the next step...but what grade of cloth will I need I see everything fro 20% to 80% available on line?
One book I have says plants start dying after 115F is this true?