I am temporarily in a smaller two car garage, about 380 ft.² I live in Colorado and the humidity is generally low, below 30%. I have a large oscillating fan that doesn't do much so I just bought a portable AC unit. It's 17,000 BTU so I thought it would be sufficient. I also insulated the builder grade garage door prior to adding the AC. Today was the first run. I started it around 2:30 when the temperature was 88°outside. The garage temperature was 85°. I ran the unit on high for nearly 4 hours and the temperature dropped 3°, barely noticeable. Since I'm living here temporarily, adding a mini split is not an option. Has anyone found a powerful AC unit that actually works?