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Kari Nöjd_Kohti resusrssiviisasta rakentamista

Modelling of extreme weather phenomena reveals wind tunnels and heat islands, making it an important tool in designing climate-sustainable urban neighbourhoods

How will the city blocks of the future deal with heavy rain or scorching heat? Adaptation to extreme weather phenomena is supported by modelling their impacts on residential areas. Read the views of Sweco’s sustainable area design specialist on developing climate-sustainable cities through modelling.

The UN predicts that two thirds of the world’s population will live in cities by the year 2050. The cities of the future must become denser, but also adapt to the impacts of climate change, such as heatwaves, droughts, heavy rains and floods. Sweco’s Urban Insight report investigates how cities can be developed sustainably while taking climate efforts into account. According to the report, the population, jobs and green areas of cities need to double in a way that improves the climate sustainability of neighbourhoods.

But how can we tell if a neighbourhood will be functional in 30 or 50 years? How will windiness change the regional conditions? How will heavy rains affect the amount of stormwater? Kari Nöjd, Sweco’s project manager on sustainable area design, works at the development stage of projects. At that stage, it is not a question of designing buildings, but figuring out how the area should be used. Sweco is continuously developing improved modelling tools to simulate the effects of extreme weather phenomena.

“We focus on preparedness and the future development of the areas. The changes in conditions caused by climate change are under investigation. We emphasise rains and dry periods that have been forecast scientifically. Our team consists of engineers who analyse and set requisites that the architects must take into account in order to create a functional neighbourhood.”

Limit values for a functional neighbourhood guide architectural design

Nöjd and his colleagues do not model the development of extreme weather phenomena as such. The specialists use existing statistical and scientific forecasts in order to observe changes in conditions in a particular region.

“It is essential that the areas we develop today will work in the future, which means that we cannot ignore adapting to and preparing for climate change. Unfortunately, we are unable to perform field tests on what the rain or drought will be like somewhere in 50 years’ time, but we can analyse areas through simulation and modelling.”

Nöjd brings up 3D models calculated by supercomputers that simulate how the built environment impacts windiness. The models show how buildings direct air flows from different directions and where unpleasant or even dangerous areas are created. When these areas are discovered already at the design stage, they can be prepared for and their negative impacts decreased.

“Another example of modelling involves the path of the sun. Simulation allows us to see how future structures, such as buildings and bridges, are shaded. Climate change will not change the path of the sun, but the strength of radiation can vary according to the future cloudiness in the area,” Nöjd explains.

Nöjd speaks of so-called heat islands. If an area is highly covered by asphalted streets, parking lots and bare roofs, the temperature can be over 10 degrees higher than in green areas.

Modelling makes design more efficient and increases understanding

Models make designing faster and more efficient while improving its quality, but another essential thing is their ability to visualise and produce understanding. For example, Nöjd was involved in a project in Siberia that included the impact assessment of windiness, sun path and climate change. There, permafrost supporting roads, houses and other infrastructure is slowly melting.

An example of the impact of simulation comes from Suonenjoki, a town in Finland, where a regional energy simulation survey of the town centre was performed. Together with VTT and Siemens, Sweco’s specialists developed a model that could dynamically simulate 170 different buildings, the district heat network and heating plants on an hourly level throughout the year. Nothing similar had been done before.

“I believe that modelling and simulation will continue to be developed and used increasingly in urban development. Land use planning is already being supported by gamification and game engines. In architectural design and engineering, game engines offer new opportunities for producing videos and animations of living urban areas. The viewer can also move around in that world and influence it. This makes visualisations even easier to understand,” Nöjd explains.


Neighbourhoods of Tomorrow: Designing for climate resilience in dense urban areas is the second Urban Insight report from Sweco in 2020 on the topic of climate action. In these reports, Sweco’s experts highlight specific data, facts and science that are needed to plan and build safe and resilient future urban environments.