We have the only stainless steel double pass flue and this just means more heat exposed to your tank of water; therefore, more heat to heat your home causing you to burn less wood. We only use a portion of our firebox and flue system to compute the BTU output of our Waterstove?. A large volume of water is an advantage to help retain those BTU's until you need them to heat your home or domestic hot water. Our furnace is eggshell tight with sprayed on urethane insulation so that virtually no heat escapes to the atmosphere and can be held for your use, thus requiring much less wood in a northern winter.Very little bending is required to load our stoves. We have a large door and our firebox is located at a comfortable height. These are very important features that allow the Taylor Waterstove?