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Take a closer look at NOx emissions

NOx emissions are the latest regulatory hurdle for boilers that installers must understand. The following information provides a brief guide on this subject.

Nitrogen oxides (NOx) released from burning fossil fuels is a relatively new issue for the UK heating industry, but one which will grow in importance. NOx emissions have always occurred, but only recently has there been any movement to limit them.

Attempts to control the environmental impact of domestic heating systems have been concentrated on limiting CO2 emissions, but increasingly attention is turning to NOx.

The key point to remember is that NOx has nothing to do with efficiency. NOx is a measurement of exhaust gases.

With domestic condensing boilers there are no models on the UK market that really emit or create high levels of NOx emissions, but with standard efficiency boilers and the prevalence of atmospheric burners, higher NOx levels were quite common.

NOx is back on the radar because emissions are an influential part of the technical guide for the Code for Sustainable Homes.

The code allocates a certain amount of points for each environmental innovation. Historically, NOx emissions have been split into five categories; however, code level 5 has now been split to introduce a new lower level of 40 mg/per kW hour which rewards the property or design with two points rather than one.

At the moment, the NOx emissions issue really only affects new-build properties, but could be taken up by existing housing stock along the way, particularly in light of the EuP or ErP Directive, which includes NOx standards.

The controversial requirement from the European Commission for NOx emissions for oil-fired boilers to not exceed 35 milligrams per kWh looks likely to be dropped, with the latest version of the directive likely to recommend NOx emissions be set at 120 milligrams per kWh.

This is still a very tough figure for UK oil-fired boilers to reach; however, this is not as impossible as the original 35 milligrams figure was.

The commission has now realised that previous drafts were not workable, particularly for the UK. We now have a practical set of proposals that can be implemented within the UK market, but which are still demanding.

The timetable for implementation starts with a new document drafted at the start of the year, followed by further consultations with representatives of member states (Defra in the UK).

Presently there are no real minimum levels required other than the already mentioned Code for Sustainable Homes. The UK is the biggest condensing boiler market in Europe and, at one time, was selling more than the rest of Europe put together.

Currently it is not that important, as installers are unlikely to find homeowners questioning them on NOx emissions. However, the key issue is that from 2015 installers won’t be able to fit a higher NOx specification boiler.

Martyn Bridges is director of marketing and technical support at Worcester, Bosch Group