Can CFD simulation improve wind comfort around buildings?

Yes, CFD simulation can meaningfully improve wind comfort around buildings. By modelling airflow patterns before construction begins, you can identify problem spots — such as downdraft zones near tall facades or wind acceleration through narrow passages — and adjust the design while changes are still straightforward and inexpensive. Below, we answer the most common questions about how CFD wind comfort studies work, what they measure, and when to use them.

How does CFD simulation model airflow around buildings?

CFD simulation models airflow by dividing the air volume around a building into millions of small cells and solving mathematical equations for wind speed, direction, and pressure in each one. The result is a detailed, three-dimensional picture of how wind behaves across an entire site — at pedestrian level, around corners, through passages, and across open squares.

The process runs in three main steps. First, a 3D model is built from geodata — cadastral maps, elevation data, and existing building footprints. Structures smaller than roughly one metre are typically left out because they have a negligible influence on the result. A surrounding buffer zone, usually around 250 metres wide, is added as simplified volumes so wind enters the model correctly.

Second, the computational mesh is generated. The air domain is divided into cells that vary in size depending on how much detail is needed. Near walls and at pedestrian level, cells can be as small as 0.25 metres. Further from the buildings, they grow to several metres. For a large urban study, a mesh can contain hundreds of millions of cells.

Third, the solver runs the wind simulation for each relevant wind direction using a turbulence model that accounts for the atmospheric boundary layer — the way wind naturally increases in speed with height. The raw output is then post-processed into colour-coded maps that show wind conditions across the site in a format you can share directly with clients, planners, or permit authorities. Our CFD simulations follow this same workflow, using OpenFOAM with an SST k-omega turbulence model and meteorological input data matched to the project location.

What wind comfort criteria does CFD measure against?

CFD results are assessed against standardised criteria that define acceptable wind conditions for different activities. In the Netherlands, the applicable standard is NEN 8100, which classifies locations based on how often wind speeds exceed 5 m/s at eye level (1.75 metres). For international projects, the Lawson criteria serve the same purpose.

Under NEN 8100, locations are assigned a class from A to E:

Class A — wind exceeds 5 m/s less than 2.5% of the time. Suitable for sitting, strolling, and walking through.
Class B — 2.5 to 5% exceedance. Good for sitting and strolling, moderate for walking through.
Class C — 5 to 10% exceedance. Good for sitting, moderate for strolling, poor for walking through.
Class D — 10 to 20% exceedance. Moderate for sitting, poor for other activities.
Class E — more than 20% exceedance. Poor for all activities.

In addition to wind discomfort, NEN 8100 also flags wind danger — locations where wind speeds above 15 m/s occur frequently enough to pose a safety risk. This is a separate assessment that matters especially for tall buildings and exposed public spaces.

The Lawson criteria follow a comparable logic but use slightly different thresholds and activity categories. We apply Lawson for projects in the UK, Gibraltar, and other international locations where NEN 8100 does not apply. Our wind engineering team advises on which standard applies to your project from the outset, so there are no surprises during the permit process.

How accurate is CFD compared to wind tunnel testing for pedestrian comfort?

For pedestrian wind comfort, well-validated CFD is comparable in accuracy to wind tunnel testing. Both methods are accepted by Dutch and international permit authorities. The choice between them depends primarily on project scale, not on one being inherently more reliable than the other.

Wind tunnel testing uses a physical scale model placed in a controlled airflow. It is well suited to individual buildings or smaller masterplans where a detailed physical model can be built. CFD, by contrast, is the practical choice for large urban areas — modelling an entire city district in a wind tunnel is physically impractical, while a CFD model can cover a domain of several kilometres without any loss of resolution in the areas that matter most.

That said, CFD accuracy depends on the quality of the setup. The turbulence model, mesh resolution, and boundary conditions all affect the result. Industry experience shows that CFD studies using validated solvers and appropriate atmospheric boundary layer profiles produce results that align closely with wind tunnel measurements when both are applied to the same geometry. Our team uses internally validated CFD algorithms and cross-checks results against wind tunnel data where possible, giving you a study that will hold up under scrutiny from municipalities and permit reviewers.

What inputs are needed to run a CFD wind comfort study?

To run a CFD wind comfort study, you need three categories of input: geometry data, meteorological data, and a clear definition of the assessment area and activities. Providing these accurately is what makes the difference between a useful result and a generic one.

For geometry, the model requires building footprints and heights for the project site and the surrounding area. Geodata sources such as cadastral maps, 3D building datasets, and terrain elevation models are typically sufficient. If your project includes buildings that are not yet constructed but have planning permission, those should be included too — they affect the wind environment just as much as existing structures.

For meteorological data, the simulation needs a wind rose that describes how often wind blows from each direction and at what speed. In the Netherlands, the NPR 6097 dataset (which underpins NEN 8100) is the legally prescribed source for permit applications. More recent datasets such as the Dutch Offshore Wind Atlas (DOWA) are also available and can be split by season or time of day, which is useful for more detailed analyses.

Finally, it helps to know what activities are planned where. A terrace, a children’s play area, and a building entrance all have different comfort requirements. Knowing this upfront means the output maps can be tailored to the questions that actually matter for your project. Our general overview of fluid dynamics consultancy services gives a sense of how this fits into a broader project workflow.

When should a CFD wind study be commissioned during a project?

A CFD wind comfort study is most useful when commissioned during the early to mid design phase — after the massing of the building has been established but before the layout is fixed. At this stage, findings can still influence decisions about building orientation, facade treatment, and the placement of entrances and public spaces.

Commissioning a study too late — during detailed design or at the permit application stage — limits your options. If the results reveal a wind problem, the changes needed to fix it (such as adjusting building height, adding a setback, or repositioning a passage) are far more expensive to implement when the design is already advanced.

That said, a wind study commissioned at the permit stage is still valuable. Many municipalities require one as part of the application, and a study that shows compliance with NEN 8100 or Lawson criteria gives the permit authority confidence that wind conditions have been properly considered. If results show issues, the report can also document which mitigation measures have been applied, which often satisfies the authority even when conditions are not perfect.

For projects with tight timelines, turnaround speed matters. We are known for our flexibility — for regular clients, we set everything aside to start the next day if needed, and our internal process automation continues to reduce delivery times.

What design changes can improve wind comfort when CFD reveals problems?

When CFD results show wind discomfort or danger, the most effective changes are those made at the urban planning level — adjusting building volumes and their arrangement — rather than adding screens or planting as an afterthought. A hierarchy of interventions, from most to least impactful, helps prioritise what to address first.

Level 1 — Urban massing: This is where the biggest gains are made. Clustering towers so they shelter each other, limiting height differences between adjacent buildings to around 30%, and orienting streets diagonally or perpendicular to the prevailing wind direction all reduce wind acceleration at ground level. A building more than twice the height of its surroundings is likely to cause downdraft problems — flagging this early gives you room to respond.

Level 2 — Building volume and orientation: Avoid placing the widest facade perpendicular to the prevailing wind. Setbacks (stepped facades) can redirect downdrafts, but they need to be deep enough to be effective — a rule of thumb is at least 5 metres of depth for every 100 metres of building height. Covered walkways provide direct protection for pedestrians but need to be at least 5 metres deep to be useful, and the area immediately beside them remains exposed.

Level 3 — Aerodynamic design and local measures: Rounded or tapered facades help wind flow around the structure rather than downward. Screens redirect local airflow but tend to accelerate wind at their edges and can affect the feel of a space. Vegetation — trees, hedges, shrubs — is effective for improving comfort but works best as a supplement to structural measures, not a substitute. Deciduous trees also lose their leaves in winter, precisely when wind speeds are highest.

Level 4 — Space programming: Sometimes the simplest fix is repositioning a terrace, entrance, or seating area away from the windiest spots. A small shift in layout can move a space from a Class D to a Class B classification without any structural change at all.

How Actiflow helps improve wind comfort around buildings

We have been carrying out pedestrian wind comfort studies since 2005, working with real estate developers, architects, structural engineers, and municipalities across the Netherlands, Belgium, the UK, and beyond. Our team knows the regulatory landscape — NEN 8100 for Dutch projects, Lawson for international ones — and we advise from the start on which assessment is needed and what the output should look like for your specific permit authority.

Here is what we bring to a wind comfort project:

Advanced CFD simulations using validated solvers and atmospheric boundary layer profiles, producing colour-coded maps ready to share with clients, planners, and permit reviewers
Wind tunnel testing for projects where a physical model adds value, such as facade pressure studies or complex geometries
Experience across all scales — from a single high-rise to city-wide area studies, including the comprehensive wind assessment we carried out for the city of Rotterdam
Fast turnaround without cutting corners on quality or defensibility
A single point of contact who stays close to your project from intake to final report
Clear, visual output — graphics and maps your team can use directly in client presentations or permit submissions

Curious how we can help with wind comfort around your building or development? Contact us — we are happy to discuss your project and help you find the right approach. You can also find out more about us and our background in fluid dynamics engineering.

Wind engineering

Indoor climate & air quality

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