Chimneys & flues
www.heatingandventilating.net The road ahead for flue installers
Dennis Milligan, president of the British Flue and Chimney Manufacturers Association (BFCMA), examines the upcoming opportunities and challenges for stove and flue installers
W
ith the increase in the price of gas, oil and electricity households are increasingly turning to wood burning stoves as an efficient and cost- effective way to heat their living space.
According to the Stove Industry Alliance (SIA) stove sales in the second quarter of 2022 were 40% up compared to last year.
Ecodesign
The Environment Bill has enshrined the significant reductions in stove emissions introduced as part of the Ecodesign regulations. To give the consumer even more confidence on emissions the Clear Skies mark certifies that a stove meets the Ecodesign emission limits or has even lower emissions. Installers need to be more aware than ever of the draw of a chimney. To
reduce emissions, Ecodesign stoves retain the products of combustion in the fire chamber longer, before releasing them into the flue. This can reduce the velocity and temperature of the flue gases when they enter the flue. To work well the stove and flue must work together as a unified system. When a new stove or flue is installed, the installer should carry out a draw test to prove that stove/flue system is working properly. It is always advisable to check the
12 December 2022
stove manufacturer’s recommendations and with the chimney/flue company. BFCMA members can advise on chimney design and installation.
Design
Most residential chimneys/ flues rely on natural draft, the pressure difference between cold and hot air, to draw the flue gases up the chimney to the atmosphere. Excessive use of bends can also cause a reduction in velocity and temperature that could reduce the draw of the chimney or flue. The best design is to have a straight chimney but where this is not possible, due the construction of the dwelling, the number of bends should be kept to a minimum and must not exceed more than four. The angle of the bends should be no greater than 45° from the vertical. When constructing a new dwelling the route of the chimney/ flue should be thought about at the design stage. Consistent insulation along the complete length of the flue is important for a
well performing chimney/flue. The last thing you want is for the temperature of the gases to fall below the dew point. Clay, concrete and pumice liners require insulation to be prepared and added on site. Stainless steel system chimneys are supplied with effective insulation. Double wall pumice chimney systems have
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