[quote=briansd1]Why do so many older houses in Vegas have the A/C unit on top of the roof? Strange. Nobody has answer that questions for me.
[/quote] Probably retrofit AC. Did the houses have ‘flat’ or ‘flat-ish’ roofs with very little if any attic to run AC/heating ducting with? The heaters may have been the old fashioned wall units. A surprising number of those old AC units may be swamp coolers (which work fairly well in the dry environment).