I have seen capped honey of 20%, as measured directly at the apiary on a refractometer. Some literature says honey of 20% mc will not ferment inside the hive, so bees will cap it and store it.
I am a very strong believer in hive ventilation.
In Guatemala, where I live, teh concept is either unknown or down right ignored. A couple of friends that IÂ´ve spoken to have risked and tried screen bottoms and upper ventilation ports. These ports are actually a built-in feature of a feeding tray that sits on the top bars.
It is rainy season now, and it is very,very humid and warm. Both these bkeepers have reported htheir hives to be dry inside, no moist rubbish collected at bottom corners, no pests like ants and roaches, and an overall look of healthy, strong hives.