A flue is one of the most important features of any stove installation. Exactly how the flue is installed can affect the performance of the stove. The flue has to be the right diameter for the stove, properly insulated as well as being as straight and vertical as possible.
A wood burning stove will be much hotter (and therefore more efficient) than an open fire. This means that the gases which are released as correspondingly hotter, which can be a problem if you intend to use a traditional chimney as a flue. Although this is possible, we strongly recommend that you have the chimney examined by an expert prior to use and if needed (which is likely) have a flue liner fitted.
An unprotected chimney being used as a flue for a wood burning stove is not terrible for the stove's performance, but the hotter flue gases will damage the brickwork. Leading to gases leaking into upper floors. If you have a thatched roof, you will need an expert to properly fit a flue or you are in danger of a thatch fire.
The other factor to consider, quite apart from efficiency, is that a flue's gases are toxic. The flue must not leak, something which is possible at the joints. An inefficient flue also risks carbon monoxide leaking from the stove as it is not extracted properly.
When installing a wood burning stove it is now part of building regulations to install a carbon monoxide detector. There is no substitute for a chimney not being in a full working order and a carbon monoxide detector is only a warning device