A roof-greening cassette, at least partially or predominantly having walls and/or bases made of (porous) material having pores, the porous material having the following properties: (a) a water absorption of 15 to 30 liters/m2 in the case of a material thickness of 30 mm, and (b) a water permeability normal to the plane of 8 to 16 liters/(m2 s), in the case of a water column of 200 mm and a material thickness of 30 mm.