something other than metal?!

We are building our first RMH!! Just a couple questions; is it efficient to have the insulated pipe, or is there another type of pipe I can use...it seems like its counter productive to use an insulated pipe when you want the heat to radiate into the mass.

why would you put insulated pipe in the bench?
where did that idea come from?
ducting works in the bench the only insulated place is around the feed tube heat riser areas.

N. Harris : Please explain a little more where you got the idea that an insulated pipe was proposed for use inside the thermal mass, the stove pipe is there because it is round,internally smooth, easily locked in place with Short screws/rivets, and sealed against leaks, but its Two most important jobs are to be a form around which to to pack our cob/stones/urbanite, and to help in radiating heat from the horizontal piping into the thermal mass . After the Exhaust gasses leave the thermal mass they should be at the planned point where the stove pipes job is to carry them out of doors vertically or horizontally and there a case can be made for the use of an Insulated Stove Pipe ! In some locations all wood stoves must vent exhaust gases to the outside of the dwelling through insulated piping ! As always please feel free to ask any questions you have here in these forums, If you were thinking it, it had to be a question in someone else's mind , together we share and learn ! Pyro - maticly yours Allen l.

I had to edit this, i had misread.

You are right the exhaust pipes are NOT insulated, the core of the heater has insulation between the burn chamber and the area where the exhaust flows downward.

Laura : find Paul Wheatons pod cast 225, and listen to Paul, and Ernie and Erica Wisner talk about upcoming changes to how we will be expecting rocket stoves to be built 12 -14 months from now !
The Heat Riser/chimney tube has been, in the past made of steel for longevity, with insulation on the outside of the tube facing the barrel.
I mention that because more and more Rocket Stove Mass Heater builders want to line the inside of the Heat Riser tube with insulation to achieve maximum high temps. This,combined with the heat radiated out from the 55 gal barrel Seems to 'create a heat engine' ( my word choice ) that helps push the exhaust gases horizontally 30 ' or more. With the introduction and further testing of ceramic refractory materials as a replacement for the Steel heat riser we have seen an increase in the burn temps, and soon perhaps we will have proof of longevity with these new materials !
This is almost exactly what you said just restated for clarification !
I am planning my next build for my self, building this way, even though I may be removing my barrel at some future time to install a new upgraded heat riser/chimney - rather than waiting and building later ! hope this helps Pyro-Al