Neil & Teresa How, Lime Kiln, Montserrat, West Indies
They work great, look great, here in Montserrat in the Caribbean.
The buildings are decagons of 8' sides, giving a floor area of a little over 500 sq ft - much larger inside than they look outside. Inspired by yurt life.
You will see from the design that there is a steel roof ring to which the 10 main rafters are secured, and the open circle was sized to take the 14" hurricane [Dade County] vent, which I had specified at an early stage in the project. No leaks from 70mph winds, true hurricanes luckily have stayed away from us so far.
The vents work fine, especially in the heat of the day with the central ceiling fan on slow speed reverse, it pushes a lot of the built up hot air through the vent and drags fresher air in through the almost always open doors and jalousie windows. Max summer temp is about 95F, minimum winter (night) 72F. Couldn't say what temperature reduction is achieved as I don't spend a lot of time with my head in the apex!
Highly recommended, and look groovy too, as us old-timers used to say..