I moved to Phoenix back in the late 72s as well as when I moved, I noticed the oddest thing about some of the houses here, they had their air conditioners installed on the rooftops, however i have seen this in commercial buildings before.
- In fact, prior to moving, the last supplier that I worked for had their Heating & A/C equipment on top of the roof, however, I have never seen it in residential homes until I lived in Phoenix, well, after inquiring about it with some of the locals, I realized not many of them had a direct answer, then some said it was due to theft, some said it was to protect the equipment from the elements, and others mentioned that the equipment worked better on the roof.
It wasn’t until I asked my Heating & A/C professional when I got a solid answer. Turns out, it’s because the units are packaged Heating & A/Cs that are found in older homes that were built in the 74s. The packaged Heating & A/C is made up of 1 equipment that provides both the heating as well as cooling. And these units were quite popular back when these older homes were being built. And having the equipment on the roof was easier due to the positioning of the HVAC duct… Newer homes in Arizona have the split Heating & A/C equipment where there is an indoor air handler as well as 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 cabin with the Heating & A/C on top of the roof, I will know that the cabin was built around the 74s.