Domestic Flue Installation

D. F. Flue Installations are based in Devon and offer both commercial and domestic flue installation services throughout the South West of England.

What is a Flue?
For any stove or fire to work successfully it must be connected to a sound chimney and a correctly sized flue. A chimney works because hot air rises. Factors such as running the appliance at a very slow rate or cold air leaking into the flue, will cools the gases down and affect the performance of the chimney.

An efficient wood burning stove or boiler produces flue gases that are cooler than an open fire. For this reason it is necessary to install an insulated liner within an existing chimney when a wood burning stove is installed to ensure that there is a sufficient draw of air. If there is no existing chimney it is possible to install a wood burning stove or boiler by constructing a twin walled flue using one of the proprietary systems.

Flue outlets must be above the roof line to effect clear, unhindered dispersal of combustion products without creating a fire hazard. The direction of the flue should be should be straight and vertical where possible. Horizontal runs should be avoided and in any event must not exceed 150 cm in length. Bends should not exceed 45º to the vertical to maintain natural draft and ease of cleaning. There should be no more than two bends in a flue. Only one appliance may enter any flue and all flues should be insulated to prevent condensation of water/tar and to protect the building against the effects of chimney fires.

Flue Liners
Houses built since 1965 have chimneys built with liners during their construction. This was usually done with a clay liner which should last the life time of the building, although may do not due to poor installation standards. Prior to 1965 lining was less common and chimneys were instead rendered with a lime mortar.

Most old chimneys need to be relined before they can be re-used, particularly those that were built without a lining or have a flue that is too big and inefficient for modern stoves and fires.

Liners in chimneys serve three main puposes:

• The liner protects the house from combustion products and protects the chimney walls from heat and corrrosion. In some tests, unlined chimneys allow heat to move through the chimney so rapidly that the adjacent woodwork caught fire in only 3 1/2 hours.
  
  
• Liners protect the masonry from the corrosive byproducts of combustion. In unlined chimneys flue gases penetrated the brick and mortar. Due to flue gases being acidic they literally eat away at the mortar joints from inside the chimney.
  As the mortar erodes, dangerous gases such as carbon monoxide can leak into living areas in the home, which is potentially deadly.
  
  
• Liners also provide a correctly sized flue for optimum efficiency of appliances. The chimney is responsible for not only allowing the products of combustion a passage out of the house, but the draft generated by the chimney also supplies the combustion air to the appliance.

For professional advice and quotes on chimney and flue installation in Devon and the South West please call Dean Fletcher of D.F. Flue Installations on 01626 864159.