HEATING, VENTILATION & SERVICES 83
Challenges & opportunities T
he regulatory framework for construction is changing; from the Building Safety Act to the Building Safety Regulator, and National Construction Products Regulator, the Building Regulations Approved Documents are also being revised.
As far as heating appliances and chimneys/flues are concerned, it could be up to five years before the review of Approved Document J (Combustion appliances and fuel storage systems) is published. New product and installation standards for wood burning stoves and flues have also been delayed by the European Commission. In the meantime, up to date information on product standards can be found in guides on the BFCMA website
www.bfcma.co.uk The new Environment Act contains the long-anticipated Ecodesign changes for wood burning and solid fuel stoves. All new appliances must now comply with the new efficiency and emission limits, and appliances placed on the market for sale before 1 January 2022 can still be sold. The Ecodesign limit for particulate matter (PM) is 55% lower than for Defra Exempt stoves – the gold standard for many years. It is encouraging that many Ecodesign stoves produce significantly fewer emissions than the Ecodesign limit, and further emission reductions are being worked on. Stove manufacturers have employed a number of design features to reduce PM emissions. 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. 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. A potential reduction in velocity and temperature could reduce the draw of the chimney or flue. A straight chimney is the best solution, but where this is not possible, due the construction of the
ADF SEPTEMBER 2022
Dennis Milligan from the British Flue & Chimney Manufacturers Association gives his view on the ups and downs for the stove and chimney/flue industries currently
dwelling, there should not be more than four bends. The angle of the bends should be no greater than 45° from the vertical. When constructing a new dwelling, the route of the chimney should be thought about at the design stage. It is always advisable to check with the stove manufacturer’s recommendations and the chimney/flue company. BFCMA members can advise on chimney design and installation. This includes using standard software to check that the flue design will create the required draw.
The Ecodesign Emission limits could also spell the end of the traditional open fire, and this could bring about a change for architects who have tended to include 200 mm flues and a standard fire opening in their detached house designs. Architects and developers may now decide to install smaller flue diameters for wood burning stoves. This will also benefit architects in the air loss calculation in SAP. The general opinion is that new open fires will not be able to meet the new Ecodesign emission limits. HETAS, the largest competent persons scheme provider for solid fuel,
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When constructing a new dwelling the route of the chimney should be thought about at the design stage
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