The Merton Rule
is named after the council in the UK that in 2003 adopted the first prescriptive planning policy that required new commercial buildings over 1,000 square meters to generate at least 10% of their energy needs using on site renewable energy equipment. The policy was developed and implemented by policy officers at Merton Council, who received corporate and political support. Its impact was such that the Mayor of London and many other councils also implemented it; and it become part of national planning guidance. Over the following few years, Merton worked closely with other authorities, professions and industry to embed the Rule into the UK mainstream. This work not only led to significant CO2 reductions in new buildings where previously there would have been none, but it also helped to support an emerging industry. In 2006 Merton won the Royal Town Planning Institute's Silver Jubilee cup for the policy, and in 2008 Adrian Hewitt (the Merton Council officer responsible for implementing and driving the policy) won the UK Heating & Ventilation Contractors gold award.
In 2008, the UK government published its central planning guidance, Planning Policy Statement - Planning and Climate Change - PPS1, that requires all UK local planning authorities to adopt a "Merton rule" policy. Receiving Royal Assent in November 2008, the Planning and Energy Act 2008 enables all councils in England and Wales to adopt a Merton Rule as well as specify energy efficiency standards over and above that of building regulations.
It was inevitable that such a radical policy would trigger a debate amongst property developers, energy companies, and practitioners. The policy has been criticised for assuming that in all cases, renewable energy generation represents the most effective method of reducing CO2 emissions at any given location. However, the policy is an incentive for architects and engineers to design and build energy efficient buildings. The more energy efficient the building, the less renewable energy is required to meet a percentage target.
The most commonly accepted threshold is 10 homes or 1,000m2of non-residential development - though this is sometimes lower. This is the accepted definition by local (and regional) planning authorities, academic institutions, trade and professional bodies, and the development, construction and engineering industries.
Not just homes
Very importantly, the Merton Rule encompasses all buildings and not just homes. As the huge number of planned houses gets built they will be accompanied by new schools, supermarkets, shopping, malls, office blocks, leisure centres, etc, and it is essential that these heavy energy users also play their part in contributing to the Government's renewable energy and climate change strategies and targets.