ᐅ Windows in a fire-rated wall

Hello everyone,
we are currently purchasing a plot of land where we plan to build an extension directly adjacent to the neighbor’s house. The building authority is now requiring the neighbor to modify their windows. Do these windows have to be completely sealed and bricked up, or would it be sufficient to cover them cost-effectively with F90-rated Fermacell boards to provide a fire protection wall?

Thanks and best regards

The certification of an F90 fire protection solution for a window that is not allowed in a fire-resistance wall is likely to be significantly more expensive than removing the window and sealing the opening with masonry. A detailed plan or concept from a fire protection expert or engineering firm may be required for the Fermacell solution.
I would avoid the extra effort. It’s not only about the 90-minute fire resistance rating (F90) but also about preventing smoke from passing through the joint areas.