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Wind effect must be taken into account for new buildings in the City of London

The City of London Corporation has published the UK’s first wind microclimate guidelines for new development proposals in the Square Mile.

Going further than established thinking, the set of guidelines raises the benchmark for acceptable wind conditions in the City, putting the comfort and safety of cyclists and pedestrians first.

The guidelines provide a more robust framework for assessing the impact of planning applications on wind conditions. They will ensure what were previously acceptable ‘business walking conditions’ are now reclassified as ‘uncomfortable’, and to be avoided other than in exceptional circumstances of limited public access.

For the first time in the UK, effects on cycling comfort and safety arising from wind microclimate are also considered. The report points out that wind can, in extreme cases, destabilise or push cyclists into the path of vehicles.

By testing roadways as well as pavements through wind tunnel studies or computer simulations, it is expected that the more robust assessment will lead to a safer and more comfortable urban environment for all, in line with greater use of the City’s streets for cycling, walking and other outdoor activities.

The City Corporation collaborated with Ender Ozkan of RWDI, a specialist engineering consultancy, and sought input from members of the wind engineering community in preparing these state of the art guidelines.

The guidelines build on complex research previously undertaken by RWDI for the City Corporation, which was awarded the Mayor’s Award for Planning Excellence at the London Planning Awards 2017.

The guidelines will also require that wind impacts are tested at the earliest point of a scheme’s design development, such as height and massing, to avoid the need to retrofit wind mitigation measures.

They will also ensure more micro-level assessments of wind directions is carried out in wind tunnel testing, apply a new rigorous code of practice in the use of Computational Fluid Dynamics (CFD) techniques, require the commissioning of two separate consultants, one to carry out wind tunnel testing and the other CFD, and interrogate any discrepancies between both sets of results and assess the variation of mean and gust wind speed and height.

As the first wind microclimate guidelines ever published in the UK, it is hoped that the criteria could form the basis for national or international standards for wind microclimate studies.

‘With the number of tall buildings in the Square Mile growing, it is important that the knock-on effects of new developments on wind at street level are properly considered. These guidelines mark another significant step that the City Corporation is taking to put cyclists and pedestrians at the heart of planning in the Square Mile, prioritising their safety and experience,’ said Alastair Moss, chair of the Planning and Transportation Committee.

‘From the Transport Strategy to the City Plan, we are ensuring that our streets are a comfortable and pleasant place to live, work and visit. We hope these ground breaking guidelines can create a blueprint for others by delivering safer, more enjoyable streets that meet the evolving needs of this great City,’ he added.