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 and the outdoor condenser
I moved to Phoenix back in the late 79s and when I moved, I noticed the oddest thing about some of the houses here, but they had their cooling systems installed on the rooftops, then i have seen this in commercial buildings before. In fact, prior to moving, the last dealer 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, and well, after inquiring about it with some of the locals, I realized not several 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, however 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 70s. The packaged HVAC is made up of 1 component that provides both the heating and cooling, then 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 and the outdoor condenser. And properly, those condensers are not found on top of the roof however instead in the yard. So, whenever I see a household with the HVAC on top of the roof, I will know that the household was built around the 70s.