First point to be aware of here is the fibre board may be asbestos based if it was installed in the 1960's.
If you are removing it you should not break the board and disturb the fibres. We would advise that this work is checked by a builder with asbestos accreditation.
It is unlikely that the dormers are insulated. You could do one of two things:
- Have a builder remove the board and reinsulated
- apply new insulation internally, this will leave the original board in place and improve the thermal performance of the dormer. Whilst this will reduce the area of the dormer it will be the intrusive, what about the rest of the roof space, we would suggest this is also un-insulated and will require the same treatment as the dormers.
