And having the component on the roof was easier due to the positioning of the HVAC duct, but newer homes in AZ have the split HVAC component where there is an indoor air handler as well as the outdoor condenser
I moved to Phoenix back in the late 79s plus when I moved, I noticed the oddest thing about some of the houses here. They had their air conditioning systems installed on the rooftops, but i have seen this in commercial buildings before. In fact, prior to moving, the last company that I worked for had their HVAC component on top of the roof, however, I have never seen it in residential homes until I lived in Phoenix, however well, after inquiring about it with some of the locals, I realized not more than 2 of them had a direct answer, and some said it was due to theft, some said it was to protect the component from the elements, others mentioned that the component worked better on the roof. It wasn’t until I asked my HVAC worker when I got a solid answer. Turns out, it’s because the units are packaged HVACs that are found in older homes that were built in the 72s. The packaged HVAC is made up of 1 component that provides both the heating plus cooling. And these units were quite popular back when these older homes were being built. And having the component on the roof was easier due to the positioning of the HVAC duct, but newer homes in AZ have the split HVAC component where there is an indoor air handler as well as the outdoor condenser. And always, those condensers are not found on top of the roof but instead in the yard. So, whenever I see a cabin with the HVAC on top of the roof, I will know that the cabin was built around the 72s.