HEATING, VENTILATION & SERVICES 29
CHIMNEYS ARE CHANGING
The British Flue and Chimney Manufacturers Association (BFCMA) gives an update for housebuilders and developers on the latest in chimney design and installation.
C
himney standards are changing. The first of a new suite of standards were published in 2019,
with more to follow in the next two years. Approved Document J, Combustion appliances and fuel storage systems, has not been updated since 2010. It is increasingly becoming out of date and does not reflect the use of new flue products and installation practices. The BFCMA is lobbying MHCLG to
update Document J as quickly as possible. The Association represents the UK in European Standards on behalf of BSi (the UK national standards body) and works closely with Government departments. As a result, BFCMA member companies are in the best place to keep you up to date on product and installation standards.
GUIDANCE & ADVICE IS READILY AVAILABLE
BFCMA members can advise on chimney design and installation. This includes using industry standard software to check that the flue design will create the required draw in the chimney. The function of a chimney or flue is to allow the products of combustion to escape freely to the atmosphere. This however is not as straightforward as it may sound. Most chimneys operate under negative pressure, relying on the laws of
STOVE MANUFACTURERS HAVE EMPLOYED A NUMBER OF DESIGN FEATURES TO REDUCE EMISSIONS UNDER THE 2022 ECODESIGN REGULATIONS
thermal dynamics to transport the flues gases up the length of the chimney/flue to the atmosphere. This requires an unimpeded flow path to the top of the flue that maintains the temperature of the gases above the dew point. Good flue design and product choice are key. A straight chimney is always the preferred option, but where this is not possible due to the construction of the dwelling, the flue design software will identify potential problems. Stove manufacturers, for example, have employed a number of design features to reduce PM emissions under the 2022 Ecodesign regulations. One of the ways in which they have reduced emissions is to retain the products of combustion in the fire chamber longer before releasing them into the flue. This needs to be factored into a chimney/flue design as this can reduce the velocity and temperature of the flue gases as they enter the flue. Chimney or flue height is also
important, both in terms of the draw of the chimney and air quality. In accor- dance with Document J the minimum chimney height recommended for the minimum performance of an appliance is 4.5 metres from the top of the appliance to the top of the chimney. It should be stressed that this is the minimum height, and some Ecodesign stoves for example may require more height. It is always advis- able to check with the stove manufacturer’s recommendations and the chimney/flue company.
SAFETY Safety is the overriding priority of the chimney standards, and BFCMA chimney and flue companies can also advise on key design features like distance to combustible material. Product testing is the backbone of setting standards.
WWW.HBDONLINE.CO.UK
Chimney and flue components are rigor- ously tested to prove that they can meet the required performance. Chimneys and flues are required to
discharge a variety of combustion gases. Different types of flue will be required to safely handle the different gases. A key feature of the chimney and flue standards is a user-readable classification system that designates the features of the flue components. The features covered include temperature and pressure rating, fire, condensate and corrosion resistance and distance to combustibles. The classification system is known as the CE Designation. With stainless steel components a label showing the classification must go with each flue component, so that its specification can be easily verified. Product standards and CE marking
apply to both flue components and to system chimneys. It is worth pointing out that a CE mark for a system chimney applies to the complete flue system, including add-on components like rain caps. The use of components that have not been tested with the flue invalidates
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
