ᐅ Insulating a cold roof: best practices for the knee wall area

Hello, we are currently insulating the top concrete ceiling with a cold roof design using 26cm EPS insulation (10 inches).
My question is how best to insulate the knee wall and fill the gaps between the beams. Would mineral wool be a better option?
Thanks and best regards

Hello, we also have an uninsulated roof with an insulated ceiling of the upper floor. So, it looks the same in our case. The gaps were not insulated at all, only covered with fine mesh to prevent any pests from flying in. Why insulate them... it’s cold anyway. I actually like it this way... I dry my laundry under the roof and am glad that some air can circulate. Best regards, Steffi33

Hello Steffi, thanks for your reply, I believe you have helped me several times before. My main concern is the small triangle under the beam.

Since I need to insulate 26 cm (10 inches) in height, the wide gap between the roof joists will automatically disappear, but I am not sure how to handle the corner under the beam. At the moment, I can only think of using mineral wool or another loose, fibrous material.

Cellulose loose fill insulation or loose-fill insulation wool

Finally finished, it was a tough job, hopefully it wasn’t all for nothing and reduces thermal bridging.

Using loose fill insulation would surely have been easier and faster, good to know for next time.