Why would home A/C units be on the roof

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i was in Vegas and i always notice that many of the home in the older areas have the A/C units mounted on the roof. Even slanted roofs . Can anyone explain why ? Just curious
 
Are they the water cooler type? I know they put those on the roof. They don't dehumidify but that's not needed in dry climates.
 
My next door neighbor had his A/C unit on the roof. It's a convenient place to put it for retrofit projects. I'm not sure about modern construction, though. Anyway, his roof started leaking. It wasn't built for all the extra weight. Had to move it down off roof, and into a spot by his garage.
 
That's a package unit. A split system has the condenser and evaporator/air handler "split" into two assemblies. The package unit has everything in one housing. As far as why to choose one over the other, that's research I'm not gonna do.
 
Package units can also be installed beside the house, with duct work going inside (practical with a crawl space, not so much with a slab house). The unit is larger than the condenser part of a split system though. A roof mount doesn't take up yard space and it's quieter.

Also more difficult to steal, which is a problem in some areas. If you're looking at houses and everyone has their ground mounted A/C inside a cage, you should consider a different neighborhood.
 
i was in Vegas and i always notice that many of the home in the older areas have the A/C units mounted on the roof. Even slanted roofs . Can anyone explain why ? Just curious
I am from Las Vegas and have experience in construction, in Las Vegas. Born and raised.

There are a few reasons, but mainly two

1.) space........houses are very close to each other, and if you also noticed, there is a 6 ft cinderblock wall around every house. The minimum space requires 3 ft walking space around every house........not much room for an ac unit. Noise from these units is magnified by the block walls, etc. Many houses are 6ft 8" from each other.

2.) dust......imagine the dust that would be kicked up in the air in the summer there. many spots cannot have grass or the like as landscape
 
It's an all in one rooftop unit.
Around here, we are about 8 degrees cooler than Vegas year round, the roof top units are furnace paks. That is, a gas furnace and air conditioner all in one. The roof is the practical place to put them since there is no crawl space to run ducts. My house has a heat pump but the air handler and duct work are in the attic. I like that my condenser unit is shaded from the afternoon sun.
 
Around here, we are about 8 degrees cooler than Vegas year round, the roof top units are furnace paks. That is, a gas furnace and air conditioner all in one. The roof is the practical place to put them since there is no crawl space to run ducts. My house has a heat pump but the air handler and duct work are in the attic. I like that my condenser unit is shaded from the afternoon sun.
Here in South Carolina new construction, no basements.
Units aren’t mounted on the roof, but in the attic.
Many of those units have gas packs.

I’m wondering if the roof thing is as others said
Because of small yards and dirt or dust
 
Gotta be space related. Crawl space ? No room on the ground floor, I would imagine. Stupid idea. The sun / rain / temp variations no good for a unit. Better off with mini-splits. HVAC companies will do anything for a buck !!!!
 
Great thread and I can't figure it out.

I live in a subdivision of semi custom homes with weather that matches Las Vegas. The lots in our subdivision are 1/3 acres. The home next door to me was built by the same builder, the same year as our home, 2019.

Both Hines are very similar in design, ranches. We have about 400 more square feet than the home next door. We have the same roof material.

The home next door has a single AC unit in their roof. Out home has two ac units, both on the ground, at exact opposite sides of the home.

For the life of me I can't understand why the home next door has AC unit on the roof. Huge amount of space to mount the AC unit at ground level

Beats me.
 
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