So what is the cut off point for an effective swamp cooler?
Most common advice I’ve heard is 50%. I’ve lived in both extremes (East Texas and SW California Desert), and I can attest that evaporative (swamp) coolers work amazingly well in the dry desert. And hardly at all in humid Climates.
Wherever you try it, one critical issue is exhaust air. Insufficient air flow will lead to an increase in humidity - which kills any temperature drop. Exhaust up high helps to blow off any heat. On those days where I elect to run an evaporative cooler in my house, I open the attic access and blow the air out through the attic, which further helps cool the dwelling.
if it were me, and I were in the SE US, I think that some type of air conditioning/humidity removal is critical. I would not waste time/money on a swamp cooler. If you own the hanger, then your options are easy. Insulate, seal, and air condition.
If you rent like many, then your options are limited. I would seal off as much as possible of the lower hanger area. Your goal is to hold a “pool” of cooler, dryer air at your level. Then I would use a dual-tube portable AC unit to blow cold air directly at the area I am working, with the side effect of some overall cooling of the general workspace.
It is important to understand the difference in portable AC types. Most portable AC’s only have a single tube which exhausts the hot air off the condenser to the outside. Unfortunately, the air they pull IN to cool the condenser comes from within the air conditioned space - creating a negative pressure in the building - aka hanger. These are very inefficient in that the negative pressure in the space pulls in hot humid air via any available opening from outside.
A dual tube portable AC pulls in exterior air to cool the condenser coil via one tube, and exhausts the resulting hot air on the other side of the coil to the outside via the second tube. This does not create a negative pressure, and thus limits exterior air intrusion.
