LANDSCAPING & EXTERNAL WORKS 89 KEEPING A COOL HEAD


With climate change already noticeably taking eff ect, housebuilders and developers must consider landscape design in this context, and get materials spec right. Jamie Gledhill of Brett Landscaping off ers his insights


T


he extreme heatwaves which characterised the summer of 2022 brought a level of risk and damage to urban environments and infrastructure which had never previously been seen in the UK.


Unprecedented temperatures led to


wildfi res which damaged numerous homes, and leading to evacuations in Dagenham, while another blaze reached the edge of the A2 dual carriageway near Dartford, causing major disruption. These wildfi res, caused by etreme heat, can be more common and are managed in rural areas, but should give housebuilders and developers pause for thought in the coming years. With periods of extreme heat likely to be a feature of UK summers, consideration will need to be given to materials used and landscape design practice that can prevent housing estates from becoming unwitting tinder boxes.


COOL THINKING


Housebuilders will need to look at the materials that are used for landscaping and at the layout of estates to fi nd ways to minimise and manage the worst effects of extreme heat. There are already products available, and research underway, on how to adapt to the changing nature of the climate at key parts of the year. While the majority of research and innovation has been focused on sustain- able drainage, and how to improve water management to mitigate large, unexpected volumes of water, there is also research focusing on how to keep paving cool and reduce the negative impact of the ‘Urban Heat Island’ effect. Industry body Interpave is looking at ways in which Concrete Block Permeable Paving (CBPP), already in wide use and a well-established SuDS technique can be harnessed to keep paving cool during the driest points of the year.


Although more research is required, the guiding principle is that porous pavements allow water to drain through rainstorms and evaporate during hot weather. Evaporation keeps the pavement cooler because heat is pulled out from the


pavement during hot weather. For these systems to be effective housebuilders and developers may need to specify a more sophisticated paving system and installation methods to harness the benefi ts. The aim is to keep a suitable volume of water, absorbed and attenuated within the paving voids. dditional interventions and fl ow control can be introduced to the system to create a ‘cooling zone’ at the base of the pavement during prolonged periods of dry weather, to supply a small reserve of water for evaporative cooling. Housebuilders can work with SuDS design specialists and manufacturers to develop a dynamic paving system that can adapt to the climate by managing water during heavy downpours, but maintains a volume of water for cooling the pavement. These CBPP systems can be integrated with other green design measures such as draining planters and tree pits to use the excess irrigation for cooling.


Furthermore, concrete block paving is a better product for ‘cool paving’ in comparison to conventional asphalt street surfaces often installed over the


original road base. Taken from locations where managing extreme heat is near the top of design challenges, there are some approaches that UK housebuilders can apply.


In the city of Phoenix in Arizona, USA, where temperatures at the height of summer average 40°C, with minimal rainfall, the City of Phoenix Street Transportation epartment and ffi ce of Sustainability have been piloting a cool pavements programme since 2020. The one-year results, presented in September 2021, demonstrated that light coloured, refl ective pavement surfaces will lower the temperature of the pavement considerably as the heat is refl ected rather than absorbed, as occurs with other surface options. Techniques developed to reduce the heat of highways in places such as Arizona are now to be found in use in projects across London, including The Bridget Joyce Square, and the Australia Road project. Concrete block paving can also be an easier product and system to use with layout alterations or reinstatements, reducing carbon footprint and whole life costs.


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