Chimney Flues Size

A standard 12 x12 flue was what we now call a 13 x13 flue.

Chimney flues size.

If the flue is circular then it should be at least one tenth the size of the fireplace opening. The rule of thumb for sizing a chimney liner is that you never want it to be smaller than the appliance exhaust hole and you don t want the liner to be three times the area of the exhaust hole of the appliance. Design velocities of larger furnaces should not exceed 10 m s. Solving your chimney s math figuring out the proper size for your chimney flue can seem like a challenge.

A modular 12 x12 flue is what we now just call a 12 x12 flue. Dimensions for square rectangular and round clay flue liner. Flues should also mirror the size of a chimney. For example an 8 x 8 square nominal clay chimney flue tile liner has inside dimensions of 6 3 4 x 6 3 4.

Quality chimney liner material that meets astm and excels in freeze thaw environments. For example you could vent a 6 inch stove into an insulated chimney that is 8 inches in diameter. Please note that the chimney pot base should not impinge upon the inside surface of the flue liner. One exception to this is that round based pots may impinge at the corners of a square flue but not by more than 3 4 in.

In the end you just want a chimney that drafts properly and allows you to enjoy your fireplace. But chimney experts and draft measurements show that in a rectangular flue not all of the cross sectional area is equally effective in developing draft. The ideal flue size is typically determined by the exhaust outlet of the stove or appliance. As i said standard flues were designed to fit with standard brick.

In most cases a step up is also fine. A cross sectional area of chimney m 2 q volume of flue gases at chimney temperature m 3 s v velocity m s. Required chimney area can be calculated as. Square flue liners are nominally sized using outside dimensions.

However generally speaking a rectangular chimney flue size should be at least one eight of the fireplace s opening. For example a 13 x13 flue can be wrapped with eight standard brick per course to build a chimney that is 21 x21. The velocity of air and flue gas in a smaller furnace should not exceed 2 m s. A 6 inch stove requires a 6 inch flue.

If a chimney s diameter is six inches then the flue should also measure six inches. A q v 3 where.