Installation of Stove using the existing chimney will require a Liner
Houses which were built anytime before the late 60’s will almost certainly need a chimney liner. These are made from stainless steel wound spirally into two concentric tubes using a special machine. They are available from at least a dozen different manufacturers and come in different grades of metal (316 and 904). It is our policy that the inner skin should be made from the higher grade 904.
Insulation of the Liner
It is our policy that a newly installed liner should be insulated wherever possible. This is usually achieved by pouring Vermiculite (mica) insulation in from the top of the chimney to fill the void between the liner and th bricks. Many installers will fit a liner without insulating it. The reasons for this are a) the expense of the Vermiculite and b) because of the extra work involved in the removal of the chimney pot and the sealing of the bottom end to prevent the insulation from escaping into the fireplace.
What is the key reason to insulate the Liner
The insulation will prevent the flue gases from rapidly losing their heat and thus causing condensation inside the liner which could, in time, prove problematical. A well insulated system makes the fire easier to light in adverse conditions and the chimney will have a better draw.
Possible exceptions as far as Liners are concerned
If a chimney has been built within the last 40 years or so, it should have a clay or pumice liner and it is therefore possible that a stove can be installed without using a stainless liner. this has the major advantage of reducing the cost.