BuroHappold calls for new thinking to solve the downdraught effect
After the recent articles published by the BBC ‘The problem with the skyscraper wind effect’ and the construction based news outlet bdonline.co.uk ‘Walkie Talkie wind complaints prompt City clampdown’ on ‘the downdraught effect’, Dr Bernardo Vazquez, BuroHappold’s leading expert in Wind Engineering and Sarah Cropley, Director reflect on the need to place people at the heart of how buildings are designed and cities planned.
Space is at a premium in most urban areas. Ongoing urban challenges are created by high-density residential, mixed use commercial buildings and the need for building spaces to work harder as the workforce number continues to increase. No matter how ‘smart’ the design, the need for citizen centric cities, matching environmental factors with urban design, development and redevelopment has never been greater.
Citizens’ needs have substantially changed within the last decade whilst urban planning criteria have largely remained the same since the 1970s. As buildings become higher, wind and its effects need to be appropriately considered within the design process. Buildings are constituent parts of cities; the relationship in terms of space between buildings needs to be thought about just as carefully as the buildings themselves.
Citizens’ needs have substantially changed within the last decade whilst urban planning criteria have largely remained the same since the 1970s. As buildings become higher, wind and its effects need to be appropriately considered within the design process
Dr Bernardo Vazquez comments that:
“Our extensive experience in masterplanning and the external urban environment analysis within the UK, Middle East and Europe, tells us that the main challenges for wind practitioners are the selection and use of the most appropriate models to aid in the design of external occupied spaces. Well established methodologies exist for the assessment of pedestrian comfort, such as the use of physical techniques (wind tunnel testing) plus the more recently introduced computer modelling techniques (CFD – Computational Fluids Dynamics). The traditional way to assess the external environment is based on the use of physical wind testing via a wind tunnel, but recently CFD has been incorporated into the design process. A common approach used by practitioners currently is to apply both physical testing (wind tunnel) and computational testing techniques, thus reaping the benefits of both types of assessment to inform building design. However, in the future computational CFD modelling may reduce the need for physical wind tunnel testing as modelling techniques evolve and are verified.”
There is currently a lack of agreed national/international guidance for appropriate wind speeds for pedestrians or vehicles. For pedestrian conditions, practitioners within the UK use the Lawson criteria to assess comfort and safety conditions in external areas. However without national guidance (via British standards or Eurocodes for instance), variations in interpretation of the recommendations can occur. Vehicles too lack guidance or accepted industry standards for Urban Designers to work within. The production of national guidance for acceptable wind speeds relating to vehicles would be an important step forward.
Fortunately future developments in the assessment/analysis of external spaces are now going beyond the analysis of wind only; temperature, solar radiation and humidity are also now being considered in the assessment of external and semi-external spaces. This opens a new set of challenges that are already being pursued by researchers and practitioners including the unification of several indices, for example the use of the Universal Thermal Climate Index (UTCI); used by BuroHappold Engineering in several projects up to date.
Sarah Cropley, Technical Director concludes:
“In order to ensure that the area surrounding the buildings we create is a great space, we need to widen our view from the building itself to the gap between the buildings. If looked at sufficiently early within a project’s conception, then small changes to the orientation or stepping/massing of a building can reduce/avoid wind downwash at pavement level, rather than needing to retro-fit often expensive and difficult solutions. Commercial value can also be created within these outside spaces, by identifying locations where the café culture can flourish within a sheltered position. The building then becomes part of the flowing urban landscape. This ownership of the outside spaces is a joint responsibility – shared between land owners, developers, urban planners, architects, engineers and local and national governments all need to be involved in getting this relatively new challenge right.”
If you would like to know more about BuroHappold’s work in urban planning or any of the issues raised here, please contact Sarah Cropley, Technical Director email@example.com: Dr. Bernardo Vazquez , Associate Bernardo.firstname.lastname@example.org: Simon Wainwright, Partner and MD Northern Europe email@example.com.