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Regulations affecting the installation of biomass systems

There are a number of regulations relating to the installation of solid fuel heating systems that apply to biomass systems. Many are derived from those originally drawn up for coal and smokeless fuel systems and may be imperfectly suited for modern biomass systems, which can cause difficulties.

Building Regulations

Building regulations place requirements on the installation of solid fuel systems, including room ventilation, flue characteristics and a fireproof hearth.

There can be difficulties with flue approval as the Building Regulation Part J (para 2.4) states that:

“Fluepipes should have the same diameter or equivalent cross sectional area as that of the appliance flue outlet and should not be smaller than the size recommended by the appliance manufacturer”

However para 2.5 states:

“Flues should be at least the size shown in Table 2 relevant to the particular appliance…”

and for most biomass appliances Table 2 requires:

  • 150mm diameter (or equivalent cross sectional area) for appliances up to 30kW
  • 175mm diameter for appliances between 30kW and 50kW.

For appliance such as small pellet stoves with a 100mm diameter flue outlet this can cause difficulties with compliance.

Clean Air Act

The Clean Air Act 1993 requires that in designated Smoke Control Areas only “authorized fuels” may be used, except in exempt appliances. “Authorized fuels” include gas, electricity, anthracite and specified manufactured smokeless fuels, but not biomass.

In order to qualify as an exempt appliance, a stove, oven or boiler must undertake specific testing. There are lists (below) of exempt appliances for the countries of the UK however many European and American appliances have not been approved, especially small pellet stoves.

Although BS EN 303-5:1999 sets emission limits, testing to this standard cannot at present be used to obtain exempt appliance status, a separate test is required.

BS EN 303-5:1999

British implementation of European standard for solid fuel heating boilers up to 300kW. Sets requirements, including for performance, efficiency and emissions, and testing and marking of equipment.

The test methods within BS EN 303-5 are used within the RHI for approval of equipment.

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