This roof can be put right onto the rafters. There are 2 types, one is prepared with rails (17cm distance) to take the roof tilese, the other is not enabling you to put on rails according to your own needs.
Both roof elements cover a surface of 1,07 m² and have a width of 20 cm.
If this insulation is not enough, an additional insulation can be put between the rafters.
Puttig battens on the rafters are not necessary. The undeside of the elements have notches each 34 cm measuring 2*7 cm saving you the trouble of removing existing battens when renovating an existing roof.