Both wind tunnel testing and CFD (Computational Fluid Dynamics) simulation are valid methods for a wind assessment — and the right choice depends on your project type, scale, and what you need to prove. Wind tunnels use physical scale models in a controlled airflow environment, while CFD runs the same analysis as a computer simulation. Both methods are accepted under NEN 8100 and the Lawson criteria, and each has situations where it performs best.
The sections below walk through how each method works, where they differ, and how to decide which one fits your project.
Which method gives more accurate results for a building project?
Neither method is inherently more accurate than the other — accuracy depends on how well each method is applied to the specific situation. A well-executed CFD simulation using validated algorithms and a detailed 3D model is just as reliable as a properly conducted wind tunnel test. What matters most is the quality of the inputs, the expertise of the team running the analysis, and whether the method suits the scale and complexity of the project.
Wind tunnel tests have a long track record in structural wind loading studies, where physical pressure measurements on a scaled facade model are well understood and widely accepted by permit authorities. CFD has matured significantly over the past decade and now matches wind tunnel accuracy for pedestrian wind comfort studies — and surpasses it for large-scale urban assessments where building a physical model is simply not practical.
The honest answer is that both methods produce reliable results when used correctly. The question is not which one is more accurate in the abstract, but which one is the right tool for your specific situation.
How does a wind tunnel test actually work?
A wind tunnel test works by placing a scaled physical model of a building — along with its surrounding context — inside a controlled airflow chamber. Engineers measure wind speeds, pressures, and forces at specific points on the model as artificial wind flows through the tunnel at calibrated speeds and turbulence levels that replicate real atmospheric conditions.
The process typically involves three stages:
- Model construction: A physical scale model of the building and its immediate surroundings is built, usually at a scale between 1:200 and 1:500. The level of detail matters — nearby buildings, terrain features, and facade geometry all influence how wind behaves around the structure.
- Testing: The model is placed in the wind tunnel and exposed to airflow from multiple directions. Pressure taps on the facade measure localised wind forces, while probes at pedestrian height capture wind speed data across the surrounding area.
- Analysis: The measured data is processed and translated into usable outputs — pressure coefficients for structural engineers, or wind speed exceedance probabilities for pedestrian comfort assessments.
Wind tunnel testing is particularly well suited to facade pressure studies and structural wind loading calculations under Eurocode EN 1991-1-4. The physical measurement process gives structural engineers and facade contractors a direct, tangible dataset they can feed into their calculations.
How does CFD simulate wind conditions around a building?
CFD simulates wind conditions by building a detailed 3D digital model of a building and its surroundings, then using numerical methods to solve the equations that govern airflow across millions of small computational cells. The result is a complete picture of how wind moves through and around a structure — without needing a physical model at all.
The process follows three core steps:
- 3D model construction: The building and its context are modelled digitally, often using geodata sources such as 3DBAG or similar datasets. Existing and approved surrounding buildings are included, and the model extends outward with simplified volumes to ensure wind enters the computational domain correctly.
- Mesh generation: The air volume above and between buildings is divided into a grid of cells — the computational mesh. Cell sizes vary from very fine near surfaces (as small as 0.25 m) to coarser at the outer edges of the domain. This mesh is what the solver uses to calculate airflow at every point in the model.
- Simulation and post-processing: A solver calculates wind velocities, pressures, and turbulence across all cells for each wind direction. The raw results are then processed into colour-coded maps and visualisations that show wind conditions at pedestrian height, on facades, or across an entire urban area.
Modern CFD tools use validated turbulence models — such as the SST k-omega model — and draw on meteorological datasets to ensure the simulated wind climate reflects real-world conditions. The colour-coded output maps that CFD produces are particularly useful for presenting results to clients, planners, and permit authorities, because they make complex airflow patterns immediately readable. Our CFD simulation approach follows this exact workflow, using internally validated algorithms and high-performance computing to deliver reliable results at any scale.
What are the main differences between wind tunnel and CFD assessments?
The main differences between wind tunnel and CFD assessments come down to scale, cost, flexibility, and the type of output each method produces. Wind tunnels rely on physical models and direct measurement; CFD relies on numerical computation and digital models. Each has clear strengths depending on what you need.
| Factor | Wind Tunnel | CFD |
|---|---|---|
| Model type | Physical scale model | Digital 3D model |
| Best for | Facade pressures, structural loading, smaller masterplans | Pedestrian comfort, large-scale urban areas |
| Scalability | Limited by physical tunnel size | Scales to city-wide assessments |
| Design iteration | Each change requires model modification | Design changes are fast to implement digitally |
| Output format | Pressure coefficients, point measurements | Full-field colour-coded maps and visualisations |
| Regulatory acceptance | Widely accepted, strong track record | Accepted under NEN 8100 and Lawson |
One practical difference worth noting: when a design changes mid-project, CFD is faster to update. Modifying a physical wind tunnel model takes time and cost; updating a digital model is comparatively straightforward. For projects where the design is still evolving, this flexibility is a real advantage.
When should a project use CFD instead of a wind tunnel?
A project should use CFD instead of a wind tunnel when the study area is too large for a physical model, when the design is still changing, or when the primary goal is pedestrian wind comfort rather than structural loading. CFD is also the practical choice for city-wide or area-wide assessments where building a scale model of an entire neighbourhood is not feasible.
Specific situations where CFD is the right call include:
- Large-scale masterplans and urban studies: A physical wind tunnel simply cannot accommodate a model covering several city blocks at useful resolution. CFD handles these scales without compromise.
- Early design stage assessments: When the building form is still being refined, CFD lets you test multiple configurations quickly and cost-effectively.
- Pedestrian wind comfort studies: CFD produces full-field results at pedestrian height across the entire site, giving a complete picture rather than point measurements at selected locations.
- Projects requiring visual output for planning submissions: The colour-coded maps CFD generates are well suited to planning applications and client presentations.
Wind tunnel testing remains the preferred method for detailed facade pressure measurements and structural wind loading studies, particularly where Eurocode EN 1991-1-4 compliance is required and direct physical measurement data is expected by structural engineers or building control authorities. Our wind engineering services cover both methods, so we can advise on which approach fits your project from the outset.
Are both methods accepted for NEN 8100 and Lawson compliance?
Yes, both wind tunnel testing and CFD simulation are accepted methods for demonstrating compliance with NEN 8100 in the Netherlands and the Lawson criteria used for international projects, including in the UK. The standard does not prescribe which method must be used — it sets out the assessment criteria and thresholds that results must meet, and both methods can produce the data needed to meet them.
For NEN 8100, the assessment measures the probability that wind speeds exceed 5 m/s at pedestrian height (1.75 m) across a range of wind directions, drawing on meteorological datasets such as the NPR 6097 dataset that the standard requires for permit procedures in the Netherlands. Both wind tunnel and CFD can generate this exceedance probability data when properly set up.
For Lawson-based assessments — common in the UK, Gibraltar, and other international contexts — the same principle applies. The Lawson criteria define wind comfort and safety thresholds; the method used to measure wind conditions against those thresholds is the engineer’s choice, provided the approach is technically sound and the results are defensible. Actiflow’s team applies Lawson criteria for projects outside the Netherlands, with experience across the UK, Gibraltar, and further afield.
What matters most to permit authorities is not the method itself, but the quality and credibility of the assessment — the methodology used, the meteorological inputs applied, and whether the results are presented clearly enough to support a planning or permit decision.
How Actiflow helps with wind assessments
We carry out both wind tunnel tests and CFD simulations, and we help you choose the right method for your specific project — whether that is a single high-rise, a mixed-use development, or a city-wide area study. With over 21 years of experience in wind engineering, we know what municipalities, permit authorities, and structural engineers need to see, and we build our assessments accordingly.
Here is what working with us looks like in practice:
- Method advice from the start: We tell you upfront which approach fits your project type, scale, and regulatory context — NEN 8100 for the Netherlands, Lawson for international work.
- Fast turnaround: For regular clients, we set everything aside and start the next day if needed. Internal process automation means we can deliver results within days for standard assessments.
- Clear, visual output: Our CFD results come as colour-coded maps and graphics you can share directly with clients, planners, and permit authorities — no translation needed.
- Full-scale capability: From a single building assessment to a large-scale urban study like the one we carried out for the city of Rotterdam, we have the computing infrastructure and expertise to handle it.
- One point of contact: You deal with one person from intake to final report. No handovers, no chasing updates.
Curious how we can help with your wind assessment? Contact us — we are happy to discuss your project and help you find the right approach. You can also find out more about our team and background on our about us page.
