The venting capacity of a rectangular or square masonry flue if translated directly into actual or measured square inches of cross section is less than a round chimney flue of the same square inches of venting capacity.
Chimney flue length.
Quality chimney liner material that meets astm and excels in freeze thaw environments.
For example an 8 x 8 square nominal clay chimney flue tile liner has inside dimensions of 6 3 4 x 6 3 4.
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Solving your chimney s math.
Chimney height also plays a role and taller chimneys generally draft better than shorter ones.
With that in mind the height of the chimney should be at least 15 feet from the floor of the fireplace to the top of the flue.
Dimensions for square rectangular and round clay flue liner.
Typical standards require a cross section area of the fireplace flue or chimney vent to be equal to 1 10 of the area of the fireplace opening itself for a conventional wood burning installation and without considering the effects of a glass fire door.