I have just dismantled my wood burner in the bedroom as it was getting clogged every year with tar crystals from the wood and the thin black Spanish pipe is far too weak in my opinion for the job this year it was rotten outside.I think the main fault was the angle at which the pipe left the house it was too horizontal so allowing the build up of the tar residue not to fall back into the stove and burn off. These crystals are formed when the hot gases meet the cold outside part of the pipe.Double skin pipe prevents this as it has a layer of air between the two skins and this allows the smoke to escape and not form the crystals. I have been to a place in I think was Tortosa which sold this stainless steel pipe it was a few years ago and I would like to have the fire reinstated.Does anyone know it's whereabouts ? I am not sure if it was Nigel who gave me directions.Anyway I found this website I would love to have mine fitted like this but here the cost does not bear thinking about.  ::) There is some great advice on the site re fitting and planning your stove.

http://www.stovefittersmanual.co.uk/articles/installing-a-twin-wall-flue-chimney/