The system, originally designed by Ernie and Erica Wisner, was first designed with an exhaust route that leads through a mass in the form of a bench/island in the living room, and out through the side of the house. This system design is very efficient.
Paul and Jocelyn, though, host many folks of various RMHexperience in their home. Paul would like to accommodate for this unique situation, and would like the system to be as close to fail-proof as possible so that both learner and experienced RMH wizard can use this heat source with equal ease.
So, Ernie and Erica came over, many a discussion were had, and a new RMH exhaust design has been realized. The vertical exhaust now goes through less of the bench/island, then snakes up towards the barrel and then up out of the house. The intention of the new design is for the vertical exhaust to be warmed by the radiant barrel, making the draw through the system easier to achieve, and thus avoiding potential smoke-back problems.
This re-route has, however, brought the whole system away from maximum efficiency. It is easier to use, but not as efficient as an RMH can possibly be. This is ok- for this house it is a good compromise.
Some of the efficiency could be recovered by using a moveable insulating board that can be slipped between the barrel and the chimney pipe when the draft boost is not needed. This would be pretty much foolproof - even if left in place when starting a fire, it would only affect the draft after the fire was already hot.