That would depend on a number of things, including the size of your furnace and heat loss rate and size of your home. Example: I replaced a 100,000 btu furnace with a 50,000 btu to heat my 1200 sq ft...
Hi: It would be nice if you would have included just why you feel they need relining and what kind of liner you have at present. But then! if we had some green eggs and ham we could have some green...
A duct is a contraption used to transfer something from one locale to another. In fireplaces, the chimney is a duct that leads the smoke from inside the house into the air outside.