On Sun, 23 Dec 2007 16:45:22 +0000, Anna Kettle wrote:

You are another person who would go for the insulated liner then ...

For preference, yes and to get the flue signed off yes also. There can be
efficiency improvements as it means you can reject flue gas at a
lower temperature and still have an effective chimney, but the woodburner
would need to be designed with this in mind. In fact there are all sorts
of reasons why an insulated flue of the correct cross section is better,
the only drawback is that the flue tends to cost far more than the wood
burner.

Some types of woodburner, masonry stoves, actually use a massive fireplace
to absorb heat and then release it into the room slowly, these burn at a
very high power and wouldn't work with an insulated flue as they depend on
the flue passage as a heat exchanger, a bit like roman hypercausts.

AJH