NigelP wrote: ↑21 Jul 2020, 17:13
Woodburner and open chimney flue. I was advised this was better than installing a smaller liner as the chimney will last a lifetime but the liners only last for 10-15 years before corroding. Aloso easier to sweep...
I am afraid you have been given some poor advice and if you are in a thatched cottage, it gets more complicated.
A woodburner is much more efficient than an open fire and the temperature in an unlined chimney becomes too cool towards the top to clear the tars etc in fuels such as coal and wood. You end up with an insufficient draught, which is bad news all on its own, and tars condense on the walls of the chimney, presenting an increased risk of a chimney fire, and the first you see of this is a nasty black stain percolating through the brickwork on the outside..... Flues are therefore required for woodburners.
In thatched cottages the same applies except that there have been instances where the flue is against the wall of the chimney (flue liners should be encased in vermiculite but it is not always possible to avoid a hotspot). If you do not line there is the danger of fires going out of the chimney through cracks into the thatch but if you do line (preferable) the problem arises that the increased velocity can serve to eject hot particles that then fall onto the thatch.
The advice is "Wood burning and multi fuelled stoves are NOT recommended for use in thatched buildings as they have been demonstrated to present a greater risk to the thatch than other forms of heating INCLUDING traditional open fires".
So unlined chimneys are good for open fires except in thatched buildings with old chimneys. Lined chimneys good for woodburners. Woodburners not necessarily good for thatched cottages if you insist on insanely hot fires because chimney fires and ejected materials are represent a greater risk......
I think that was it - my head hurts
Oh - and only cheapskates put in liners that are not high quality stainless steel........
For those living in thatched cottages who are now concerned there is some guidance from Historic England and a wonderful 87 page report is available at:
https://research.historicengland.org.uk/Report.aspx?i=16101&ru=%2fResults.aspx%3fp%3d1%26n%3d10%26rn%3d49%26ry%3d2018%26ns%3d1