Fins

Does anyone know why so many new buildings have fins?

Edit: I've now looked it up and as MariainWales and others suggested below, it is for 'passive low-energy cooling of buildings'. Fins can be moveable or fixed and their orientation depends on whether they are on the north, south, east or west of a building.

Now I'm interested. There will be another blip.

I'm a bit ashamed of not checking in the first place - I blipped this one in too much of a hurry.