Insulating flat topped bay window

-taff

I have two bay windows, both are flat topped, both are quite cold.
I intend removing the plasterboard from the upstairs one, as there are not enough areas that are stable enough to screw in a curtain rail [ the window surrounds, upvc, butt right up to the plasterboard] to add some more points to screw into, probably a bit of 2x1 attached to the surround on the inside.

What's the best way of insulating this bay? The plasterboard is freezing to the touch and has leaked and been badly filled/repaired in the past so there have obviously been problems with the outside waterproofing before. There doesn't seem to be a problem with it now, but I will check before assuming.

Kiran

If you are stripping all the plasterboard back then PIR board (rigid insulation) such as kingspan or celotex. You need to leave an air gap between the insulation and the roof covering. If you are going to strip the old roof covering off then consider a warm roof construction. This is a better detail in my opinion if you can accommodate the extra depth as you eliminate cold bridging from the roof timbers.