Don't know about evaporative cooling. Would that be *inside* the shop, or a
water tower-type deal outside the shop?

Direct sun on roofs is a killer, and likely much worserer in a metal
building.
I think I've heard of insulating paints, that might help.

But *any* kind of air gap would help enormously to reduce the load. If you
have a flat roof, any kind of skin or sheathing a few inches off the top (a
foot or so would be better) would help. I scattered milk crates over an
exposed flat tar roof. Helped!!

An air gap *inside* the building, w/ exhaust forced air, would help also. A
hung ceiling would do very well. Could cut your A/C costs proly in half.
Also reduces the volume requiring A/C/heat.
If you hung a ceiling, in the winter/cold you could direct that hotter air
back into the shop space.
--
Mr. P.V.'d
formerly Droll Troll
"Dave Lyon" wrote in message
news:a962g.908004$x96.138352@attbi_s72...

While we're on the subject...


My shop is a 4000 square foot metal building with just a little
insulation.
I've got 2 residential air conditioning units that keeps it bearable, but
not comfortable in our Missouri summers. I've heard that our humidity is
too
high to use an evaporitve cooler in this area effectively, but I've always
wondered how one of those would do in a shop that has two central air
units
running non stop. Would it actually add any cooling? Would it cause my
equipment to rust? It would sure be cheaper to operate than a 3rd AC unit.