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If the existing flue is tested and leak-free, is it compulsory to get a liner fitted?

When installing a wood burning stove or a multifuel stove into an existing chimney around 75% to 80% of the heat produced goes into the room, with an open fire 75% of the heat goes up the chimney. This means that the amount of smoke and the heat produced from a stove is far less than a solid fuel open fireplace. This cooler smoke will never draw through the chimney as fast and the result of this is that a wood burning or multi fuel stove will never bring the operating temperature of the chimney up to the level it was intended for. This will more than often result in the chimney not drawing properly and the smoke, which is un-burnt fuel, will condense causing soot deposit build up. Even more dangerously this will cause tar deposit build up which cannot be cleaned away by a chimney sweeps brushes and tar build up on the chimney will result in a chimney fire. One sign of tar, or otherwise known as creosote, is where is leaks through the bottom of the register plate or through the mortar joints of the chimney. This is why it is always a good idea to insulate a chimney where ever possible or required.

We prefer to use Chimwrap, as this wraps around the liner itself and does not transfer moisture unlike vermiculite. Vermiculite is a well know insulation used with lining chimneys and fitting of fireplaces, however we have seen it in it’s wet state in chimneys and it transfers moisture all the way down the chimney. This is caused by bad chimney lining installations not terminating the lining system at the top of the chimney correctly and water penetrating the chimney. Or, more commonly the pointing on the chimney has not been well maintained along with flashing coming loose and water entering the chimney through the bricks.

This is why we prefer to use Chimwrap where ever possible, as any water leaking from pointing failing in future years after our installation will not be soaked up by Chimwrap, creating damp issues the through the whole chimney, it would show up quicker in a localised location on the chimney, normally at the first bend in the flue. This is a better situation than the whole chimney becoming damp. Chimwrap does cost slightly more than vermiculite, but this is because it is a better product that does the job. Vermiculite in our humble view is not always the best type of insulation.

The truth is, if a chimney were pressure tested 80% of chimneys would fail if they were Victorian or Edwardian properties as the chimneys are always in bad condition after years of usage, cold weather and rain damage.  With a gas fire, the gases in the flue cool and cause acidic condensation, which is very bad for the inside of the chimney.  Solid fuels leave soot deposits that need to be swept every year at least once.  This regular sweeping and high temperatures from the solid fuel can mean that the chimney can fail the year after it was confirmed safe to use.  Therefore, it is best practice to line the chimney before installing either a gas or solid fuel appliance.  Otherwise, the fireplace or stove might have to be removed to install a flexible liner.  In some cases, it is possible to line the chimney with the fireplace intact with the use of our Eldfast Ceramic Lining System.

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