As developers seek to promote comfort and safety in recreational spaces through sustainable urban development, Rachel Brown, Senior Planner at Deloitte, assesses the importance of Environmental Impact Assessments (EIA) – particularly in terms of external microclimate – in the planning stage.
The comfort and safety of users in recreational spaces is an imperative requirement for planning approval and is crucial to the success of large scale developments. As a result, EIA requires the developer of tall buildings to embark on the detailed study of external microclimate from the earliest stages of development proposals to ensure the end design is suitable within the existing urban landscape.
Practising as both a coordinator of planning applications and coordinator of EIA, I have witnessed first-hand the benefits of expert advice and testing, and how it is now best practice as opposed to an added extra to undertake microclimate studies during the development of planning proposals.
These detailed studies from the earliest stages of development proposals ensure the end design is suitable within the existing urban landscape, creating attractive and comfortable places to live, work and visit.
While there exist various means of testing, the two most common methods are desk-based and the wind tunnel test.
As a first step, at an early stage in the design development, experience-based wind microclimate assessments using desk study methodology can provide useful guidance to design development by way of identifying key areas of potential impact on ground level conditions and the likely extent of required wind mitigation schemes.
Identifying a range of potential mitigation measures can then be tested to make the most out of wind tunnel time. This means that when a scheme, should it be deemed necessary, goes into a wind tunnel or CFD analysis, it is more likely to yield helpful results.
In cases where you have a proposed building that is tall in its context, it has the potential to catch accelerated winds and change wind conditions at ground level. Detailed wind modelling studies are recommended to provide quantification of ground level impacts in terms of accepted comfort and safety criteria. Once comfort and safety classifications have been derived the wind environment can be easily interpreted in terms of the suitability for the intended pedestrian uses, thereby allowing the need for inclusion of wind mitigation schemes in further design development to be gauged.
There are a number of key benefits to this testing. Perhaps the most significant is that knowing the potential wind microclimate issues early on results in mitigation measures to be designed into and embedded within the scheme, thereby forming part of the design development process.
Furthermore, identifying ‘red flags’ early on before the design is fixed avoids a retrospective design which may distract from the original vision and subsequently incur delays in obtaining planning permission through redesign, further assessment, and discussions with the local planning authority.
In advance of defining functions of a development, early testing can assist in the design and functionality of areas best placed in terms of areas to dwell. This ensures they can function correctly and maximise their potential. For example, a café with outside seating which is sheltered from adverse wind conditions will have a better prospect of success compared to if located in an area of problematic comfort ratings.
From a financial perspective, costing wind testing and mitigation up front reduces the danger of the development halting due to lack of funding available to incorporate measures and prolong the overall delivery of the scheme. In addition, early testing avoids complicated planning conditions on the decision notice, which may delay commencing development.
Knowledge and awareness of the potential problems upfront results in a proactive rather than a reactive process, with measures being incorporated into the scheme as opposed to an afterthought which ultimately may diminish the overall quality of the development.
In summary, wind testing is an extremely useful tool for tall buildings and constrained sites. The costs associated of not testing can be significant both in time and money. Nevertheless, there is also a necessity in gaining the right balance between early testing and ongoing design changes to the extent where re-testing is required. Similarly, wind testing itself is a costly process and therefore a proportionate approach is important and to only undertake wind tunnel testing where necessary; obtaining expert advice as first step is key to understand the wind dynamics of a site and input early into how the design can be evolved to take into account any potential issues.