Steve B wrote:
I got my 1200+ sf roof on my shop. It has no peak, just a slope. I
was given a HVAC study here that some organization did that said with
foam sealing, and water flowing over the outside of the roof, a 25F
degree reduction was capable. Has anyone ever used flowing water
over the roof of a building or carport or plain roof to attain
cooling?
Would like to hear your stories.

No first hand experience, but a couple of sites deal with the question of
cooling an ATTIC while you're working there. The two best recommendations
were a water sprinkler on the roof and disconnecting one or more of the
ducts and let the house a/c cool the attic. Anyway, the watered roof is easy
enough to test.

Set up a soaker hose or sprinkler on the high side of the sloping roof and
let 'er rip. Measure the shop temperature both with and without the water
running. See if there's a significant difference.

Now for a thought experiment:

Assuming there IS a significant difference, the first thing is to find a way
to marry, in a leak-proof manner, some aluminum electrical conduit to a
water hose. Then drill itty-bitty (I'm talking really small, 1/32 or less)
holes, one every inch, along the pipe and install on the high side of the
roof. Turn on the water.

I say teeny-weenie holes because you want the water to exit the pipe the
entire length, not all coming out close to the hose connection. If you make
the holes TOO small, you can easily correct that with the next size drill
bit.