Because sedum roofs have shallow root systems and low growth rates, they won't become overgrown and won't need watering, deadheading, or mowing; all that's needed is an annual feed, some weeding, and a check to make sure the green roof is draining properly.
The sedum roofs significantly improve the fort Kudelstaart's insulation. By evaporation, green roofs cool the fort's roof during summer, while sedum roofs insulate the building from the cold in the winter. Last but not least, placing sedum roofs at the solar panel installations will boost their effectiveness.