Currently there are no building regulations that say you must insulate your chimney liner when installing into a chimney stack.
There is however a regulation in place though where gases must be vented safely out a building.
Insulating your chimney liner ensures that waste gases are safely vented and travel externally away from the burning appliance.
If your existing chimney is located on an outside wall it is advised to insulate your liner, similarly if you have a large chimney stack it is also recommended.
Choosing to insulate your chimney liner, ensures that gases are safely vented and will travel directly up from the multi-fuel stove.
So by insulating your chimney liner within