A comment on roof evaporative cooling system. I was involved back in about 1984 on a roof top system here near the coast of NC with a similar, although simpler and cheaper system which I will attempt to explain in detail.
This was done on insulated poultry houses and my home. The timer set up was similar with the exception of we ran for approximately 3 min out of 15 and adjusted for max benefit. We attempted to have zero run-off to maximize the water to heat removal ratio -- this would be adjusted for your area etc. I don't remember the exact timer used but it was a one hour repeatable timer -- very inexpensive. We ran from water supply with 1/2 pvc to peak of roof. The pipe was then run across peak of roof using plastic conduit clamps.
Before putting the pipe on roof we perforated it every 3 ft with a NAIL. We found the easiest way was to use a drill press turned off and press the nail point until it just perforated the pipe (this took time but after depth was determined, it went quickly). I actually used a bench grinder and flattened out the flat sides effectively sharpening the edges on a number 8 nail before use. This created a diamond shaped pattern which caused the water to fan out somewhat instead of a stream. We experimented with hole placement at different pressures etc and achieved some dramatic results from this. The 300 ft poultry houses saw an "attic" temp decrease, measured at peak of roof, of an average of 30 degrees during a 20 day period in July- August when roof temps were 115 -120 degree avg. My home which I ran slightly longer cycles due to black shingles I ended up running about 3 min in 10 and saw dramatic attic temp drops which I don't have documented but I remember being in the same range as poultry house but having more effect inside the house due to different cooling types. This was very inexpensive I actually used a defrost timer from an old refrigerator and cut notches with grinder to activate solenoid. Use this and experiment and let us hear results.