Flue liner: A flue liner is a round or square tube that fits inside the chimney flue (its inner vent). Some flue liners are made of clay, so they don't rust, but many are made from corrosive metal.

Installing an insulated flexible aluminum flue liner in your chimney Published: Aug. 28, 2007, 1:56 a.m.

One of the chimney repair people, however, says the problem is our high efficiency furnace, and that the condensation that occurs in the chimney from the good heat is crumbling the bricks.

Q. Our house was built in 1965 and has an interior chimney with three flues, each with clay liners. One flue is unused and was probably installed for a connection to a furnace that was not needed ...

My house is 1906 vintage, and a chimney sweep recently told me that I had a serious hazard because of not having a lining. Evidently buildings constructed before 1924 did not have them. Any comments?

Either way, these extreme temperatures can crack clay flue liners and bricks, vaporize mortar and warp metal chimney seams. Passages for flame and gases will have been opened.

What if I don’t have professional maintenance? Some zero-clearance fireplaces will have a metal flue that goes through basically a wooden box void, which is like a fake chimney, Jesberg said.

Ask the Remodeler: Does your chimney need a metal liner? Plus, advice on replacing wooden porch screens. By Mark Philben Globe Correspondent,Updated February 6, 2022, 12:00 a.m.