Outdoor Cookstove Chimney & Secondary Air

Continued from here.

Almost done! For the cookstove chimney, Dan used the old ductwork we saved when our HVAC unit was installed. Why didn't he use double-wall stovepipe? Primarily, because the stove is in an open outdoor space; the chimney doesn't pass through walls, ceiling, or roof. In a house, building codes would require it to keep the house from burning down. Outdoors, we just want the smoke vented away from us as we're cooking. Secondarily, because the design of a masonry stove is such that 90% of the heat is retained in the stove rather than going up and out the chimney. That means that the stovepipe doesn't reach the high temperatures of a conventional woodburning stove.

Part of what helps the efficiency of our design, is the secondary air intake.

Secondary air tube

It fits into a channel built into the bottom of firebox (core). Click here for core construction photos here.

Dan welded an L-bracket to the tube to
keep firewood from hitting the air pipe.

When the door is closed, air is drawn through the tube under the door to the back of the firebox, where smoke and heat exit through a narrow side opening called the "port." This narrow opening slows the exit of the smoke, and when combined with heat from the fire and the extra oxygen from the secondary air, allows wood gases to be burned. The result is increased burn efficiency. (The concept is better explained at this website.)

Next, the chimney.

The insulation is non-combustible rock (aka mineral) wool.

How well did it work?!?!?!?!? More on that here.

Outdoor Cookstove Chimney & Secondary Air

© Nov 2021 by Leigh at http://www.5acresandadream.com