Dry park with deck chairs

The urban climate – what do we need to know?

I recently chaired a very interesting urban climate session at ARCC and CIBSE’s urban microclimate event. Here I report on conversations from the discussion groups – while these are not my opinions, there is much that I agree with.

Firstly, delegates were asked to consider what information do we know we are not using, and why?

The discussions concluded that the causes and impacts of the urban heat island (UHI) effect are well understood, however, less is known about available tools and models to help designers and planners combat the issue. Concerns were also raised about accessing models and data without getting entangled in the inherent complexities, and as a result using a lot of time that design fees would not cover.

Participants identified the wealth of information held by the GLA, and I suspect there are other useful GLA data sets and innovations we didn’t hear about as the event was not London focused. BRE have a UHI map of London and have also mapped the effects of the UHI in a specific year (2008).

To sum up, there is a fair amount of knowledge and data available, with more for London than anywhere else.

What do we need to know?

How should we examine the impact of hybrid areas? ‘Hybrid’ was understood to mean tall buildings and green roofs. This raised the question should we aim for a city that is one huge tower block surrounded by green areas, or dispersed low-rise buildings, like parts of Paris?

Participants commented on how much additional concrete is needed for green buildings, and queried how much green buildings do actually affect the urban climate. Mention of blue infrastructure was also made – while we are all aware that green and blue areas are important to ease urban climate challenges, there appear to be few metrics to measure the impacts. Establishing legal minimum / maximum standards for developers is an important task that needs to be addressed.

As more cities collect big data, questions were raised about how we actually analyse and use big data, and what the socio-economic impacts are.

Air quality is an area of concern across the UK – there are a number of useful tools to measure air quality which will help to enable mitigation strategies. While authorities such as the GLA and Kingston are working together to explore the impacts and solutions, more data is required from cities other than London.

Delegates discussed how useful mapping of the urban climate would be, and the need for a guide on how urban form relates to microclimates in order to help practitioners.

What’s next?

The workshop confirmed that it is vital for academics and practitioners to continue to mix: academic tools can be demonstrated and further developed to help practitioners, while practitioners can help researchers to understand what information would be most valuable, and the depth of detail they require for their designs.

Delegate’s suggestions and comments:

What do we need to know?

Models and planning processes capable of accounting for how cities evolve (land use, planning, human behaviours) in climate change scenarios.

New measurement protocols and parameterisation, capable of being used in different environments with cross-comparison of results possible.

Improved understanding of how green and particularly blue spaces can mitigate the UHI.

Better definitions –particularly of high density and appropriate density in relation to quality of built environment.

Research to reveal how air quality and thermal quality correlate within the urban heat climate to inform urban form and building design with regard to ventilation and passive cooling.

How to link measurement of city performance (heat, pollution) with investment.

Building-level fire safety standards exist. Are there wider area standards, for coping with multiple building emergencies in a dense urban setting?

What do we already know but are not using, and why?

Real time and empirical data for validation of models –suggestion that practitioners might not be aware of what’s available.

Current planning policy:

  • Evidence presented suggests policy on daylight, sun and wind need updating.
  • A microclimate perspective reveals negative unintended policy consequences e.g. air source heat pumps are encouraged but add to microclimate overheating.

Making urban research models more accessible could be helped by:

  • Establishing if they better than commercial “black box” models?
  • Improving the user interface and data set compatibility and integration with existing planning tools
  • If specific real time datasets are required, consideration as to whether local authorities should be mandated to collect them.

How are we going to tackle or take it forward?

Produce a standard for city modelling and a standard data-sharing clause in funding bids, taking into account confidentiality, intellectual property and privacy laws.

Research outputs need to be disseminated quickly and simply to practice and industry.