I recently installed two large dehumidifiers, at a cost to me of under $500, in a building that simply is too large to air-condition. I've been pleasantly surprised by the results.
Our large out-building is cinder block with a metal roof. The ground floor was built into a hill on the southeast side, which provides some natural cooling at the cost of being damp, causing mold to form in spots on our camper as well as anything else left there. The upper floor bakes in summer, and until later year, could be difficult to enter on a hot day. Last year I added more circulating fans, which did help move air around on both floors, but the humidity persisted.
Now with the dehumidifers running, for a few dollars each month, the entire building is dry and pleasant (downstairs) and tolerable to pleasant (upstairs). I can now work on cars, farm machinery, or carpentry projects without dying of heat stroke.
I set the target relative humidity at 60% for each floor. The units have a garden-hose adapter and the water goes under a garage door to the outside. These units can remove tens of gallons of water from the air daily, but there's not enough of a drop to collect the water in a barrel, something I'd like as I use distilled water from our home AC to flush the radiators in our cars, when I change coolant. I will figure out a system later. Note the starting humidity after I had the bay doors open for 30 minutes. Within half an hour of closing the doors, we were back at 60%.
Such adaptations won't solve all problems, even when I install solar on our property to reduce our carbon footprint. Meanwhile, parts of each floor remain more humid that others, though the circulating fans help reduce that problem. For those like me with a large garage but little money for HVAC, this solution may help you as human-driven climate change makes our summers ever less pleasant.
