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The Merton Rule

The Merton Rule was a ground breaking planning policy, developed by Merton Council, which required new developments to generate at least 10% of their energy needs from on-site renewable energy equipment, in order to help reduce annual carbon dioxide (CO2) emissions in the built environment. The rule applied to all types of buildings, not just homes.

Merton Council developed the rule and adopted it in 2003. Since then the Mayor of London and many councils implemented it, and it became part of national planning guidance.

Our planning policies have since changed, and the Merton Rule has been superseded by new energy requirements in building regulations.

On this page

The policy text

"The council will encourage the energy efficient design of buildings and their layout and orientation on site. All new non residential developments above a threshold of 1,000sqm will be expected to incorporate renewable energy production equipment to provide at least 10% of predicted energy requirements.

"The use of sustainable building materials and the re-use of materials will also be encouraged, as will the use of recycled aggregates in the construction of buildings. This will be subject to the impact on the amenity of the local environment, taking into account the existing character of the area."

The justification sets out that where the incorporation of renewable energy equipment would make the development unviable it will not be expected. So for example for technical reasons it may not be possible to mount solar or wind methods on a roof.

The justification also sets out the means of generating renewable energy to be photovoltaic energy, solar-powered and geo-thermal water heating, energy crops and biomass, but not energy from domestic or industrial waste.

Making a difference

Merton Council worked with other authorities, professions and industry to embed the Merton Rule into the mainstream, and was instrumental in persuading the UK Government to include an addition in its national planning policy guidance (PPS22), confirming the legality of such policies. With the policy nationally accepted, Merton officers have been working with others to spread good practice and knowledge.

The Merton Rule has led to manufactures of energy related construction products changing product lines. For example, after hosting a series of seminars, addressed by Merton officers, Mitsubishi Electrical developed a new range of heating and ventilation equipment that would meet the Merton Rule requirements. The Merton Rule is proving to be a boost to industry in the sector.

We have estimated that if applied nationally the application of the Merton Rule equates to an annual total renewable energy infrastructure industry of £1,125,000,000 - delivering a CO2 reduction of 160,000 tonnes.

Furthermore, if the Merton Rule policy is adopted for new housing by every council, it will trigger sufficient growth in the industry to create economies of scale that will reduce equipment costs to the point where they will become affordable to homeowners who want to 'retrofit' their homes.

How the policy was applied

Below is an outline of how the Merton Rule policy was applied:

  • Compliance with the policy is required as a condition of the planning consent. Until this condition is signed off the development will not be legal.
  • In order that the developer can get a clear idea of the costs it will be helpful for them to enter into discussion prior to submission of an application.
  • The basis for the 10% calculation is simply the energy consumption of the proposed building multiplied by the floorspace of the development.
  • Where speculative commercial/industrial development is intended and the end user cannot be identified fittings are not included in this energy assessment. This results in a reduction in the electricity use with only lighting being considered.
  • To work out the energy consumption we use the Energy Use Benchmarking Guides that have been produced by BRE (Building Research Establishment) for the Department of Trade and Industry (DTI). These guides give the energy consumption per metre squared for various building types, for example an open plan office with natural ventilation. A total figure should be worked out separately for gas and electricity values and then combined.
  • Energy consumption is then converted into carbon by multiplying by a simple fraction. This then gives the total carbon consumption for the building from which the 10% requirement can be determined. The figure is converted into carbon because of the differing quantities of carbon dioxide produced when generating electricity or producing heat from a gas boiler. Electricity generation produces more.
  • This is the figure that the developer has to satisfy and it is up to them how they do it. We meet (if necessary) initially to agree this figure and can meet further to negotiate ways of meeting the target. For example if energy efficiency measures are to be incorporated as standard into the building such as energy efficient lighting and increasing the thermal mass of the building then this will reduce the overall carbon footprint of the building thereby reducing the 10% requirement.
  • It is usually cheaper to reduce the energy consumption of a building than provide renewable equipment. Therefore if a building exceeds the requirements of the forthcoming Part L of the Buidling Regulations then we will take this into consideration and reduce the energy consumption for the development.

2008 conference

Merton Council hosted a conference about the Merton Rule in 2008. The speakers' presentations are available below.

Merton's current policy

The inclusion of energy requirements in building regulations has superseded the need for a prescriptive renewable energy targets for new development for an outer urban borough like Merton. We have adopted a new approach; as set out in Core Planning Strategy policy CS15 of the Local Development Framework, using nationally recognised sustainable design and construction standards. However, our new approach does not exclude the effectiveness of implementing ‘Merton Rule’ style renewable energy policies in other areas where there is greater scope for, and likely more effectiveness, from renewable energy installations.

See also

Related websites

Contact us

Strategic Policy and Research
Future Merton
London Borough of Merton
12th Floor Merton Civic Centre
London Road
SM4 5DX.

Telephone: 020 8545 3837
Fax: 020 8545 4160

This page was last updated on Monday 10 October 2016

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