Chimney Height for a Downdraft Pottery Kiln: The Draft Pressure Needed and the Height Beyond Which Fuel Use Barely Falls

This paper addresses downdraft kilns that stall, smoke back, or burn unevenly because the chimney provides too little draft. It presents a chimney-height selection rule based on stack draft pressure, derived entirely from stated assumptions and a computation whose code and full output accompany the paper. The sweep covers chimney height from 2 to 10 m. The headline outcome is: best x 3; best fuel kg 427.2; draft at best pa 22.3; fuel at 2m kg 453; fuel at 10m kg 514.6; saving best vs 2m pct 5.7. These figures identify a specific operating point or bound that a workshop can apply directly, and they also show how quickly performance deteriorates away from it. No kiln was built, no ware was fired, and nothing was measured for this study. SIMULATED, NOT MEASURED.