When should you commission a wind assessment for a project?

You should commission a wind assessment as early in the design process as possible — ideally during the concept or preliminary design phase, before key decisions about building height, orientation, and massing are locked in. Whether a study is legally required depends on your project type, location, and the applicable local regulations. The questions below cover the most common situations project managers and structural engineers run into when navigating wind studies.

Is a wind study legally required for your building project?

In the Netherlands, a wind study is not always a statutory requirement, but municipalities increasingly demand one as part of the permit application for tall buildings, large-area developments, and projects in densely built urban environments. The legal basis varies per municipality and project type, so the safest approach is to check with the local planning authority early.

In practice, most projects involving a building that is more than twice the height of its immediate surroundings will trigger a request for a wind comfort assessment. Rotterdam, Amsterdam, and other major Dutch cities have embedded wind assessment requirements into their spatial planning policies. For projects in the UK, a wind assessment is routinely required as part of an Environmental Statement for planning applications, particularly for tall buildings in city centres.

Even when a study is not legally required, commissioning one voluntarily is often the smarter move. Discovering a wind problem after planning permission has been granted — or after construction has started — is far more costly than addressing it in the design phase.

What’s the difference between a wind comfort study and a wind loading assessment?

A wind comfort study assesses the wind conditions experienced by pedestrians at ground level around a building or development. It answers the question: is it comfortable and safe for people to walk, sit, or linger in this outdoor space? A wind loading assessment is a structural calculation that determines the wind forces acting on a building’s facade, cladding, and load-bearing structure. These are two fundamentally different studies, serving different purposes and different audiences.

Wind comfort studies are relevant for urban planners, architects, and developers who want to understand how a new building will affect the public realm around it. The results inform design decisions such as building orientation, the placement of entrances, and the need for wind screens or canopies. Wind loading assessments are used by structural engineers and facade contractors to size structural elements correctly and comply with construction standards such as Eurocode EN 1991-1-4.

A third type of study worth knowing about is the large-scale area assessment, which covers an entire district or masterplan rather than a single building. This type of study is useful for municipalities and developers working on major urban regeneration projects, where the cumulative wind effect of multiple new buildings needs to be understood as a whole. Our wind engineering services cover all three types, from individual building assessments to city-wide studies like the one we carried out for the city of Rotterdam.

At what stage of a project should a wind assessment be commissioned?

Commission a wind assessment as early as the concept or schematic design phase. The earlier you introduce wind into the design conversation, the more options you have to address problems without significant cost or delay. Once the building’s massing, height, and orientation are fixed, your ability to make meaningful changes is limited.

A useful rule of thumb from our knowledge base: a building that is more than twice the height of its immediate surroundings is at elevated risk of causing wind problems at street level. If your project meets that threshold, a quick scan or expert opinion during the early design phase can tell you whether a full assessment is needed and flag any obvious risks before they become expensive ones.

For permit applications, the timing is also practical: municipalities and planning authorities typically require a wind study to accompany the permit submission. Commissioning the study too late means it sits on the critical path and can delay your application. Building in enough time for the assessment, any design iterations it triggers, and the final report is straightforward when planned from the start — and much harder to manage when it becomes urgent.

What happens if wind problems are found late in the design process?

If a wind assessment reveals problems after the design is largely fixed, your options narrow considerably. Structural and architectural changes become expensive, and some of the most effective mitigation measures — such as adjusting building height, orientation, or massing — may no longer be feasible. That said, there are still meaningful interventions available at later stages, though they tend to be more costly and less elegant than early-stage design changes.

The mitigation hierarchy works roughly like this, from most to least effective:

Urban planning level: Clustering towers so they shelter each other, keeping height differences between adjacent buildings below 30%, and orienting streets diagonally or perpendicular to the prevailing wind direction to prevent channelling effects.
Building volume and orientation: Setbacks (recesses in the facade) are effective when deep enough — a minimum of 5 metres for a building of around 100 metres tall. Avoiding the widest facade facing the prevailing wind direction also helps significantly.
Building-level additions: Aerodynamic facade treatments, covered walkways, and wind screens can reduce discomfort at specific locations, though screens tend to accelerate wind at their edges and are less visually appealing.
Public realm adjustments: Planting, sunken seating areas, and repositioning entrances, terraces, and play areas away from the most exposed spots. These are useful but should not be the primary line of defence.

The important principle here is that wind problems are much harder to solve at building level if wind has not been considered at the urban planning level first. Late-stage mitigation is always a compromise.

Which norm applies to your project — NEN 8100 or Lawson?

For projects in the Netherlands, NEN 8100 is the applicable standard. It classifies wind conditions at pedestrian height based on the probability that wind speed exceeds 5 m/s (for comfort) or 15 m/s (for safety), expressed in hours per year. For projects outside the Netherlands — including the UK, Gibraltar, and international locations — the Lawson criteria are the most widely used framework, though some cities such as London and Leeds have their own specific guidelines.

Under NEN 8100, wind comfort is classified on a scale from A (best) to E (worst), with each class linked to acceptable activities: sitting, strolling, or passing through. Wind danger is assessed separately, with an exceedance probability above 0.30% for 15 m/s classified as unacceptable. The meteorological input for Dutch assessments is based on KNMI wind data, with the NPR 6097 dataset legally prescribed for permit procedures.

The Lawson criteria follow a similar logic but use different threshold values and activity categories. If your project spans multiple jurisdictions, or if you are working in a country without a formally prescribed standard, we can advise on which framework applies and what the relevant planning authority will accept. We apply both NEN 8100 and Lawson across our projects in the Netherlands, Belgium, the UK, and beyond, and we are familiar with the specific requirements of individual municipalities — which matters when you are preparing a report that needs to hold up under scrutiny.

What inputs does a wind consultant need to start an assessment?

To start a wind assessment, a consultant needs a 3D model of the proposed building, information about the surrounding built environment, and the intended use of the outdoor spaces around the development. The more complete and accurate this information is at the start, the faster and more useful the assessment will be.

In practice, the minimum inputs needed to get started are:

A 3D volume model of the proposed building (or buildings), including height, massing, and key architectural features
The project location, so the surrounding context can be modelled using geodata sources such as 3DBAG or equivalent
The intended uses of ground-level spaces — entrances, terraces, play areas, public plazas — so the assessment can evaluate comfort against the right activity categories
Any relevant planning documents or permit requirements that specify which standard applies

For CFD-based assessments of larger areas, the consultant builds a computational model that includes all existing and permitted buildings in the surrounding area, typically within a radius of several hundred metres. Details smaller than about one metre are generally omitted, as they have a negligible effect on results. Meteorological data — wind speed and direction distributions — is sourced from established datasets such as KNMI’s NPR 6097 or DOWA, depending on the project and the applicable standard.

You do not need a finished design to get started. An early-stage volume model is enough to run a quick scan or expert opinion, which can already tell you whether the project carries significant wind risk and what design directions are worth exploring. The Actiflow overview gives a good sense of the range of services available depending on how far along your project is.

How Actiflow helps with wind assessments

We work with project managers, structural engineers, architects, and municipalities at every stage of the design and permit process — from early-stage quick scans to full CFD assessments and wind tunnel tests that meet the requirements of permit authorities in the Netherlands, the UK, and internationally.

Over 21 years of experience with wind assessments in the Netherlands and Belgium, including familiarity with the specific requirements of individual municipalities and planning authorities
Full range of assessment types: expert opinion and desk study, quick scan CFD, full CFD assessment, wind tunnel testing, Environmental Statement wind chapters, and large-scale area studies
Both NEN 8100 and Lawson criteria covered, with experience in the Netherlands, Belgium, the UK, Gibraltar, the Middle East, and Southern Europe
Clear, visual output — colour-coded maps and graphics produced using our advanced CFD simulation technology that can be shared directly with clients, planners, and permit authorities
Speed and flexibility: for regular clients, we set everything aside to start the next day if needed, and our internal process automation keeps delivery times short without compromising quality
Single point of contact from intake to final report, with engineers who understand both the technical and regulatory side of wind studies

Curious how we can help with your wind assessment? Feel free to contact us. We’d be 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.

Wind engineering

Indoor climate & air quality

Aerodynamics for R&D