I have been using a split door vertical CharBroil smoker for the past 1.5-2 years, overall it is a pretty poor performing smoker unless you have time to babysit during the smoke. So I decided I was going to modify the existing unit with material I already have from salvage and recycling. I hate seeing things thrown away and am forever collecting materials/objects I feel can be repurposed. For the walls I used a left over sheet of cement board from my home remodel, reclaimed wood from pallets that I collected and leftover cutoffs from assorted projects. I will be using scrap hvac ducting from a local business remodel for the chimney. I will be using 1.5" ball valves for lower air control to wood/coal basket that I removed from an old vacuum sealing station at my office. Wood/coal basket was made from scrap expanded steel cutoffs. This spring I will be using 3" stainless exhaust pipe and v-band flanges to couple a keg with the smoker for an external firebox, but I have to wait for the weather to turn to pull my car out of storage in the garage to finish this step of the project. It's a work in progress but I should be running the first smoke with phase one this weekend to get a good idea of improved efficiency over the factory setup.