Hi everyone, it's my first time posting after almost a year of reading this forum. I've learned so much from everyone! Thank you all.
We're currently in the process of restoring a late 1800's victorian terraced house. It's of a typical L shape to the back with a side return.
We have a disused chimney on the rear gable end and the stack is shared with our neighbours. Their chimney is also not operational.
On the ground floor there is an additional room which extends beyond the chimney. This is original to the house. On the first floor the stack is built into the gable end of the house.
See drawing below of the layout.
On both floors the fireplaces are blocked but our pots were left open. (Yes I did find 130 years worth of bird skeletons and nests inside!)
My question is about how best to insulate this? Should I fill the flue with insulation from the top and seal it off? Or should I insulate the interior walls around the chimney and leave the stack empty?
Has anyone done something similar? If so what did you use? If possible I would like to fill it in order to save floor space inside as we will be insulating the other external walls with wood fibre board.
Though I'm aware it would be a massive cold bridge at the back of the house if we don't insulate around it.
I'm currently slating the roof and this will probably be my next job before the scaffold is gone. So not afraid to get stuck in and do it DIY.
Our engineer advised filling with concrete, but I do not like this idea for lots of reasons.
Appreciate any advice, thanks.

We're currently in the process of restoring a late 1800's victorian terraced house. It's of a typical L shape to the back with a side return.
We have a disused chimney on the rear gable end and the stack is shared with our neighbours. Their chimney is also not operational.
On the ground floor there is an additional room which extends beyond the chimney. This is original to the house. On the first floor the stack is built into the gable end of the house.
See drawing below of the layout.
On both floors the fireplaces are blocked but our pots were left open. (Yes I did find 130 years worth of bird skeletons and nests inside!)
My question is about how best to insulate this? Should I fill the flue with insulation from the top and seal it off? Or should I insulate the interior walls around the chimney and leave the stack empty?
Has anyone done something similar? If so what did you use? If possible I would like to fill it in order to save floor space inside as we will be insulating the other external walls with wood fibre board.
Though I'm aware it would be a massive cold bridge at the back of the house if we don't insulate around it.
I'm currently slating the roof and this will probably be my next job before the scaffold is gone. So not afraid to get stuck in and do it DIY.
Our engineer advised filling with concrete, but I do not like this idea for lots of reasons.
Appreciate any advice, thanks.
