I also remember hearing that old houses in FL were built with tall ceilings to help cool it off… which seems the opposite of what’s most efficient for home A/C’s??? Feels like I’m missing something.
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A tall ceiling does not make air conditioning more efficient, that is efficient in energy usage.
The wall area of the building increase if you increase the ceiling height and the result is higher energy exchange with the outside.
The increased energy usage will be less for a large building than for a small one. the reason is the walls are a smaller part of the building.
Consider a house that might be 15 x 6 meters, the floor area is 90 m^2 and so will a flat roof. The circumference of the house is 2 x (15 + 6) = 42 meters
The inner ceiling is a bit over 2 meters so let’s say a 3-meter building height. The wall area is 3 * 42 = 126 square meters. So a total of 126+90 = 216 m^2 outside air. I am ignoring the floor because the ground will be cooler than the outside air.
Increase the ceiling height by 2 meters and the total outer area is not 5*42 +90=300 m^2. It is an increase of 40%
A store at 80×80 meters has a floor area of 6400 m^2 The circumference is 320m If the walls are 3 meters the wall area is 3*320= 960 m^2 and at 5 meters 5* 320= 1600 m^2 Notice the walls have a smaller area than the roof in this case but are lager then the roof for a small house.
So the total area is 7360 m^2 and 8000 m^2 the increase is only 8%
Larger ceiling height makes it easier to install for example air ducts and it makes it feel a lot larger at a relatively low cost. So even if you need a bit more energy for cooling installation of the system to transport the air and another thing will be lower with a high ceiling.
You can do a similar calculation and just look at the area hit by the sun but the result will be similar.
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