A solution for weathering the future

Phil Allen, Senior Civil & Flood Risk Engineer at Thomasons, explains how we need to design & adapt our buildings to mitigate against the effects of extreme weather, believed to be an effect of climate change

2019 has been another year of climatic records and extreme weather events in the UK, from the highest temperature ever recorded in the UK to heavy rainfall and severe flooding, which threatened homes, businesses and lives in the North.

Extraordinary weather is the new norm and its effect on society is profound. Whether it is the economic cost of damage to buildings and infrastructure from flooding, or to human health from living in hotter, more polluted environments, the building industry must take steps to meet the challenges of extreme rainfall and rising temperatures.

As the atmosphere grows steadily warmer, its capacity to store moisture increases. This is creating bigger, more powerful storms, more extreme rainfall events and subsequent precipitation-related flooding.

How can we design and adapt our buildings to guarantee they remain fit for the future and mitigate the impact of major weather events?

While storms are releasing greater quantities of water in shorter periods of time, spells of relative drought and potential water shortages may follow. The dispersion of surface water is only half the answer. We need to cultivate a smarter, more balanced relationship with water in our developments placing green thinking at the forefront.

Where many of our clients are based in Surrey, there is already regulatory pressure on new developments to limit rates of surface water discharge to greenfield runoff. Pollution mitigation is also a key consideration, often achieved through attenuation, flow control and soakaways.

These are good engineering solutions, but they are focused on mitigation rather than adaptation. The next step must be to encourage developers to move away from hard engineering designs and to explore environmentally led, soft engineering solutions.

Green or brown roofs are one such example. While not a novel solution, ‘living roofs’ only started becoming legal requirements in various cities and countries around the world in the last decade, recognised for their ability to counteract the effects of climate change.

Up on the roof

As part of a sustainable drainage system, green roofs can intercept and store rainwater. They release surface water at a slower rate into the drainage system while transferring moisture back to the atmosphere through evapotranspiration. Green roofing systems also have the potential to filter and improve the quality of the water before it enters the drainage system. When faced with limited space for rainwater attenuation or habitat creation and greenspace, they should be a key consideration for developers looking to construct sustainably.

As well as offering a number of environmental benefits, green roofs can also be advantageous to people in urban areas. They can mitigate local air pollutants and boost thermal performance, either through cooling buildings in the summer months through evapotranspiration, or by providing better insulation in the winter. This can help reduce energy consumption.

Using green roofs in the built environment can also moderate the heat island effect, conducive to significantly lower temperatures than those of conventional roofs and reducing ambient daytime temperatures. Along with benefiting to the environment, it can also help city-dwellers get a better night’s sleep!

Hotter, drier summers lead to further overheating in urban areas, which is particularly concerning for the population’s most vulnerable. Thus green roofing can also help tackle the other major threat from climate change: rising temperatures’ threat to public health.

A collective effort

Beyond green roofs, there are many other design and construction strategies that enhance building sustainability and mitigate the effects of climate change, from material choices through to other social and economic decisions.

Overall, a collaborative approach from all involved in delivering new developments is needed to adapt infrastructure and buildings to cope with climate change effectively. Clients, consultants and research institutions all have a role to play, from demanding buildings which are fit for the future to supporting the industry with design guidance and training.

Finally, the regulators should continue to incorporate climate change adaptation into upcoming policies and hold developers to account that don’t provide sustainable designs.

Phil Allen, Senior Civil & Flood Risk Engineer, Thomasons