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As for your question on cooling my shop/garage, at first I tried installing a small -- much too small at about 5500 BTUs -- AC unit in a box in the ceiling. I rigged it so that the hot air would be able to float up into the attic. This really didn't work well, which I later found out was because the attic air is so hot to start with that there is not enough temperature differential for the condensor/compressor-thingie in the AC unit to go its job correctly. So the AC unit would blow cool air for a while, but it would gradually get warmer and warmer, until I could hardly tell the difference.
I improved on this a bit by installing a large, cheap fan on top of the box in which the AC unit fits -- rigged so that it goes on when the AC unit is on, and blows air straight up. Thus, it pulls air from the garage to cool the freon-stuff in the AC unit. This worked better so far as cooling goes, but the AC unit itself is still annoyingly loud.
The big breakthrough came when our house's main AC unit sprang a leak and the old repair guy who came out to fix it told me how to do it the right way. It's so simple it's almost stupid. Just cut a hole in the main outfeed leading away from the AC coil so that cold air spills from the house's AC unit into the garage. Either install a closeable vent in that hole or rig up something like a DC blast gate, so you don't air condition the garage all the time.
Remember though, that before I did this, I insulated the garage door with about 3" of rigid foam and the garage attic with at least 8" of blown insulation. Thus I'm hopeful -- perhaps naively so -- that it will not make too huge a difference in our overall power bill. (We have not yet received one since I made the change.) If you were to try this without first installing heavy insulation, I think you could bankrupt yourself paying for the electric.
HTH, 