Sealed Surfaces:
Building Climate Resilient Cities

Wide streets, large squares, ample parking – urban sprawl and increasing transport infrastructure construction means that more and more natural land is being sealed with impermeable surfaces. As a result, managing the challenges of extreme weather conditions such as overheating and heavy precipitation is becoming more difficult. The wienerberger subsidiaries Semmelrock and Pipelife offer solutions for permeable concrete paving and efficient rainwater management that equip cities to adapt to the consequences of a changing climate. 

According to the European Environment Agency the surface area of cities in the EU has increased by 78 percent since the mid-1950s. Population growth, urbanization and economic development are exacerbating this trend. Although land take is now slowing, hundreds of square kilometers in the EU alone are still sealed each year, for example with asphalt, preventing penetration by air and water. Where surfaces are completely sealed, very little rainwater seeps away and evaporates. This is why intense rainfall often overwhelms sewer systems and leads to flooding. Moreover, the interruption to the natural water cycle causes the groundwater level to fall, with consequences ranging from subsidence to local water scarcity.

Climate change is increasing the frequency and intensity of extreme weather conditions, such as drought, severe precipitation and heatwaves. This is the conclusion of the current Assessment Report of the Intergovernmental Panel on Climate Change IPCC. Unsealing soil and green spaces makes a positive contribution to adapting to climate change. Unlike sealed surfaces, paving stones and turf pavers laid over a permeable base allow rainwater to seep away through wide gravel or grass joints, or through drainage holes, so that it can soak into the ground where it is stored.

One aim is to maintain the natural water cycle. The lasting water infiltration performance of Semmelrock pavers has been confirmed by expert opinions from the Neuwied Material Testing and Research Institute Neuwied in Germany. The wienerberger subsidiary offers special pavers with a high degree of permeability (Eco Paving) and is constantly looking for ways to improve them. Take for example, the turf pavers in new formats with a hole geometry that offers a drainage area of up to 30 percent. “Innovative developments by Semmelrock combine function and aesthetic appeal with excellent permeability and improve the micro-climate,” explains Christian Weinhapl, Category Manager Concrete Pavers at wienerberger. Moreover, concrete pavers are 100 percent recyclable. Read more here: Semmelrock: From Paver to Paver.

When surfaces are sealed, almost all rainwater runs off into the public sewer system. Together with underground retention, storage and infiltration systems, concrete pavers can help prevent local flooding and reduce the burden on the sewer system. “Well-designed complete solutions are essential for enabling cities to cope with severe precipitation,” says Ulrich Bohle, Category Manager Infrastructure at Pipelife.

From fall 2022, Semmelrock will offer its own gutter drainage system in southeast Europe to supplement its pavers. The system diverts rainfall into the sewer system or the modular rainwater management system Raineo^® from Pipelife, as torrential rain can cause flooding even on unsealed surfaces.

Thanks to Raineo^® rainwater is collected underground, filtered and channeled into retention cisterns, known as stormboxes. These boxes hold back precipitation, thus preventing the sewer system from coming under additional stress in the event of heavy rainfall. Afterwards, there are two options: the water can be reused – for example, for irrigation purposes. “Another option is to let the water slowly seep into the ground, maintaining the stability of the water table,” says Ulrich Bohle. Read more here: Smart Rainwater Management.

The issue of overheating in cities is an additional and growing problem for urban residents since cities are disproportionally affected by global warning. Urban heat islands are an increasingly frequent occurrence in high temperatures. However, this effect can be mitigated by using suitable materials. “Even the color of paving stones can minimize heat stress. Light-colored surfaces have great potential as they have a high solar reflectance index (SRI),“ says Christian Weinhapl. 

Dark surfaces with a low SRI absorb and retain more solar heat, which is then released with a time delay during the night hours. In comparison, light-colored pavers store and emit less solar energy as they deflect most of the sun’s rays. Supplementary measures, such as providing shade by planting trees and other forms of vegetation or creating bodies of water in the city, also mitigate the urban heat island effect.

wienerberger is concentrating resources across the entire group to develop innovative solutions for adapting to climate change. The company’s experts work closely with stakeholders in the areas of urban climate resilience and green urban architecture. At the same time, wienerberger does its utmost to minimize its own impact on the environment at every stage of the value chain. Read more here: How we Live ESG at wienerberger.