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The Danger of Merton

Opinion The Merton Rule could lead us down a blind alleyway as we aim to go green, says Peter Fisher

The Merton Rule, pioneered by the London Borough of Merton, requires schemes to use renewable sources to produce at least 10 per cent of the energy used on site.

But the most effective way to reduce CO2 emissions is simply to not use energy. In new buildings this is most effectively done through better passive design rather than through bolt-on renewables.

CO2 emissions can be reduced at little cost by using intelligent, passive and importantly inherently good design – which in large part means keeping glazing ratios down.

The danger of Merton for architects is that it removes the emphasis from good inherent design and instead concentrates effort on the least effective and most expensive way of reducing CO2 emissions. A few token wind turbines placed on the top of a fully glazed office building will save only a fraction of the energy that a sensibly designed facade will.

However, the issue is muddied slightly because it is often hard to tell whether or not installed renewable technologies and passive design measures are delivering the savings they claim to. This highlights the urgent need for much more objective post-occupancy data on actual performance, so that informed and objective decisions can be made.

This, in turn, requires national postoccupancy standards rather than prescriptive technical solutions, and a separate renewable feed-in tariff. The first will drive the most effective reductions in emissions from new buildings – be they delivered through passive design or renewables – while the second will make renewables more feasible across the whole building stock rather than just on the small number of new buildings.

The key in any post-Merton debate is understanding that there is a fundamental difference between industrial policy and standards for new buildings.

In the absence of any other wide-scale policy mechanism, Merton has been Britain’s most successful policy driving renewables. It has unquestionably had a huge positive impact, but changes are needed. More ambitious CO2 emission reductions are required across new and existing buildings.

Renewables have a role in new buildings, but the energy savings that can be made by using good passive design need to be considered before they are used.

Peter Fisher is an associate at Bennetts Associates

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