When looking at new developments it is always important to consider the environmental impact that the building might have on the surrounding area. When looking at developments in busy cities one of the important factors is pedestrian comfort and safety as a result of the change in wind microclimate.

Wind Microclimate

Changes to the built environment, from building new structures, to removing existing buildings, can have a significant impact on the local microclimate and conditions experienced by the residents and users of those spaces. One of the major impacts caused by changes to the built environment is the effect on local wind conditions. The introduction or removal of a large structure can have substantial, and even surprising changes, on the wind speed and direction. When considering the wind microclimate, the massing and locations of the buildings relative to the wind conditions at the site will determine the level of impact that wind will have on and around the proposed development. The common industry standard analysis is to compare the calculated wind levels against the Lawson Comfort Criteria for pedestrian comfort and safety, which will give an indication to any mitigation measures which may be required at the proposed development.

Wind Microclimate Specialists

By using Computational Fluid Dynamics (CFD) modelling our engineers provide accurate models which analyse how the wind will affect a space. We assist in modelling real-life spaces that are suitable for their intended design use and above all, are safe for all those using the area. Where a tall or large development takes place, it is common for local authorities to require a wind microclimate assessment to be submitted as part of the planning application process. Xi Engineering helps at all stages of the design process from concept through to the planning stage and provides input to Environmental Impact Assessments (EIA).

Wind Microclimate as part of the planning application process – environmental chapters

In submitting a planning application, it is common to include wind microclimate assessment chapter as part of the wider Environmental Statement. Our wind microclimate modelling team are experts in producing the wind microclimate chapter along with the associated technical summary. We also help to advise the architects and project design team regarding mitigation where it is required, providing simulations to support any recommendations.

Wind Microclimate Assessment

Whilst there is some variation depending on the local authority, the basic requirements of all assessments are to ensure the comfort and safety of those in and around the new development. As well as assessing whether wind conditions are suitable for a given environment and intended usage for a space, the assessments will also look to evaluate whether a space is safe, particularly for vulnerable users. Where mitigation is required to resolve unfavourable wind conditions, Xi’s Computational Fluid Dynamics (CFD) modelling approach can quickly and efficiently be used to test changes to development layout and environment feeding back quickly to the project architects and designers.
Our assessment includes:

• Combining local wind statistics with Computational Fluid Dynamics (CFD) simulations to assess the wind speeds at pedestrian level.
• Comparing statistical wind speeds against the Lawson wind comfort criteria to determine the effect on pedestrians.
• Assessing the effectiveness of possible mitigations and suggesting solutions

Computational Fluid Dynamics (CFD) Wind Modelling

When resolving a wind microclimate assessment, it is important to understand how a space will change following a development and then again over time where other significant developments take place nearby. Therefore, it is common for at least two models to be built and often a third if appropriate. These models will consider the wind conditions in the following scenarios:

• The existing baseline conditions
• Following the new development
• The new development in conjunction with any neighbouring development schemes

Wind data specific to the development site will be fed into the model and the wind velocity profile calculated for each model for a range of wind directions.
For each scenario that is modelled, the wind environment will be assessed between models to evaluate if the change in the built environment will result in a beneficial or an adverse change to the wind microclimate. We regularly undertake CFD wind studies using industry-leading software SimsScale, partnering closely with architects, developers, councils, civil & structural engineers and planning consultants to simulate how air flows around new developments.

City of London Wind Guidelines

To help ensure a more comprehensive and standardised approach to wind microclimate assessments the City of London introduced “Wind Microclimate Guidelines For Developments In The City Of London”. The very large skyscrapers and dense construction within the City of London have led to concerns that the urban wind microclimate may lead to wind speeds capable of knocking over vulnerable road users, cyclists and pedestrians. The new guidelines set out some key requirements that must be followed when planning a new development and set out the steps a wind microclimate assessment should follow.

Environmental Statement Chapters

Further to carrying out Wind Microclimate Assessments, Xi’s wind microclimate expertise is regularly called upon by industry leaders for the review of Environmental Statement Chapters as part of the planning process. For more information on this service please visit our Environmental Statement Creation and Review page.

Why Choose Xi Engineering?

Our specialised team has extensive experience simulating complex wind microclimate models. By early involvement in a project, we can help you avoid last-minute delays in the planning process. By using detailed Computational Fluid Dynamics (CFD) modelling our team will identify potential issues with pedestrian safety and comfort and suggest realistic solutions as well as providing support throughout your planning applications. Contact our team to talk in more detail about your enquiry and offer complimentary guidance for the next step of your project.

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