9. Keep the chimney warm by keeping it inside.

The other thing that has a big impact on temperature is of course exposure to the elements. You may have noticed that in all the illustrations in this series, the top few centimetres of chimney have always been given a bluish tinge. This is to illustrate the fact that we can do nothing to stop the head of a chimney being cooled by the weather.
XXWe can however do something about keeping the rest of the chimney as warm as possible. The best way is to locate it within the main body of the house (A). Not only will this raise the operating temperature several vital degrees – it will also ensure that heat lost from the chimney percolates into the building where it will do some good instead of being lost to the cold night air (B)
XXIf a chimney is badly located the end result will always be the same; degradation in performance and the prospect of long-term maintenance head-aches.
XXSometimes when a chimney is suspected of running cold it is worth examining the amount of fouling up that occurs at the extreme top. A warm chimney that's running well will tend to precipitate a crust of soot and tar in the top half metre only – where the flue gasses are chilled suddenly. A cold running chimney may appear to be relatively clean at the extreme top, for the simple reason that most of the really nasty stuff has been precipitated further down.