I’ve been wondering about this.Potentially daft question here... why is that insulation necessary? It's certainly not to keep the warmth in for the fans sat below... is it as basic as keeping pipes from freezing over winter?
Interestingly, it looks exactly like the acoustic insulation I bought for the internal walls and downstairs ceiling in our extension a few months back. Same brand and colour.
But saying that, it has thermal properties, too.
It may well be for thermal regulation. To stop excessive expansion and contraction of the main roof structure.
It won’t be to keep fans cosy, because of the pitch-sized hole in the middle. But it might help keep heat off in the summer I guess.
It also won’t be to keep sound in, as that acoustic insulation absorbs sound. Perhaps it’ll help absorb stadium vibrations from fans / noise too?