The importance of wind assessment
Cities become denser. We build more and more high-rise buildings, but these buildings typically induce high wind speeds on pedestrian level. As such, high buildings can reduce pedestrian wind comfort and the attractiveness of an entire neighborhood, but they can also lead to dangerous situations, especially for elderly or physically vulnerable people. Therefore, it is important to reduce high wind speeds in public spaces. A wind assessment gives you insight in local wind climate and how you can prevent wind hindrance and improve wind comfort.
But a wind assessment can also be used to determine how wind can help to solve another problem, such as increasing temperature in densely populated cities. These cities have difficulties to cool down, especially at night. The heat that is accumulated during daytime is trapped within the dense boundaries of the built environment. Significant research on this matter is performed at Eindhoven University of Technology (Toparlar Y, Blocken B, Maiheu B, van Heijst GJF; 2017; A review on the CFD analysis of urban microclimate. Renewable and Sustainable Energy Reviews 80: 1613-1640). Research shows that increased temperatures in our cities leads to an increased mortality, mainly for people over 65 years of age, due to cardiovascular and respiratory problems. To mitigate this problem, wind can play a major role. Wind can help to ventilate streets, to dissipate heat, and as such, to cool down our cities.
Guidelines for smart cities to design wind in public spaces
In many places in the world, (local) governments and municipalities start realizing the important influence wind can have on the quality of life in our cities. However, we now see that wind assessments are mainly used to study problems when they already exist, and if assessments are used in the design phase, they are used to check the impact of a single building or project, when the design is almost fixed.
Wind is a large-scale phenomenon, and therefore it should be taken into account on a large scale in a city. This means that wind effects should not be studied or solved on a building level, but in an entire area or neighborhood. Moreover, it is important to study the impact of a new development already in an early phase, when it is still possible to change building volumes, the landscape design or the orientation of buildings and streets. In a later phase, when the design of each single building is almost ready, a final check for pedestrian wind comfort can be performed and possible issues can then be mitigated with smaller measures like adding vegetation or small canopies or screens.
At Actiflow, we advise governments as follows:
- Assess the impact that wind has in your city, but also look at other aspects like shading, sound, heat islands, mobility, air pollution, etc.
- Determine the critical areas in the city, and consider how the challenges can be solved on a large scale (e.g. open up or densify the urban texture, introduce parks or other landscape elements, determine where high-rise buildings can be allowed, determine the orientation of important streets and corridors, etc.)
- Determine which quality standards you want to achieve, depending on the local function of the public space
- Translate the large-scale solutions and quality requirements into practical guidelines and codes for developers and architects: which building volumes are allowed, how to orientate the volumes, what is the maximum building height, where to place entrances or private outdoor spaces, and how to prove that a building design meets the requirements.
If good guidelines and rules are in place, developers and architects can easily check for each of their concept designs if they comply or not. By involving wind assessments during the design process, possible local issues can be identified in an early phase and the impact of a design modification can easily be assessed. When the building design is fixed, a final check can be performed to show compliance with the norms set by the government. A great example of this approach is the Amstel III area, where the municipality formulated guidelines and requirements for real estate developers.