Rocket Stove query

I'm wondering how important it is to insulate the heat riser section of a rocket stove? I'm thinking of just using some old flue. Any help out there? Thanks.

Graaly

It is critical to have an insulated riser. Temps inside run 1500 F + .    You want to keep that heat traveling up to strike the top of your barrel and do a complete burn . An non insulated riser is going to shed its heat outward not up , your rmh will not draw  well and you may end up with smoke back, plus excessive ash buildup .  Just not a good idea.  

Buy the builders guide or the dvd collection or both to understand how a rmh needs to be built to function properly.  

Build it by the book the first time. You can always play with design changes later, outside ... after you have a perfectly working wonderful  rmh in your living room.  

Legend, thanks Thomas. Much apprecaited.