tallen1950

tonyv, we installed a SUPRA wood burning stove last year with a single pipe of interconnecting tubes. The problem you outline has confirmed my thoughts also. From the very beginning we had tar dribbling down from the interconnection points. The wood we bought was "sec" however I suppose any gases given off from even the dryest wood can condense if they get cool enough. Our pipe is vertical and about 4m long. Enough for the temperature to diminish below boing point I suspect. Anyway having taken further advice it seems the double paroi is the solution most likely to solve this problem. If as you say it makes the flue temperature higher (which it should) and then the stove more efficient, it should pay for itself in the long term. Many thanks for your comments.  I will ask the chimney guy about mechanically redistributing some of the heat.