Here it is, my roof temp measured inside the R-19 attic space dropped from 136 deg F to 90 deg F in about 30+ minutes. It stayed down for almost 2 hours, so watering 2 x 3 times per day could really help to keep you cool.
Cheaper and faster then air conditioning if you need it.
In my case it works great because I have standing water between the ribs.
136 deg F to 90 deg F