According to the latest forecasts, a heatwave is imminent across Europe, with southern and southeastern Europe expected to see temperatures rise to 46 degrees Celsius in the coming days.
For example, in Italy, authorities have issued a ‘red alert’ due to dangerous weather conditions in seven cities, including the capital, Rome.
Cities are set to be particularly affected by the rising temperatures, where high levels of sealing with heat-retaining materials can make urban areas up to 15 degrees hotter than surrounding rural areas.
“This so-called ‘heat island’ effect is extremely damaging to health,” says Gregor Grassl, an associate partner and head of green urban development at the consulting firm Drees & Sommer. “Dehydration, cardiovascular problems, and respiratory difficulties disproportionately affect older and health-compromised individuals.”
The silver lining is that cities and municipalities are not powerless in the face of the climate crisis, Drees & Sommer suggests. Here are five recommendations to combat urban heat islands:
1 – Ensure Sufficient Shade
The simplest and most cost-effective method to protect streets and open spaces from heat is through trees or other shading elements. “Urban tree cover is crucial,” explains Grassl. “Trees not only provide shade but also cool the air through evaporation.”
In Rastatt, Germany, for example, approximately 1,000 newly planted trees have contributed to cooler summer temperatures while absorbing CO2 and pollutants, enhancing air quality.
2 – Cool with Green Facades and Decentralised Areas
Greening urban spaces and reducing sealing play vital roles in improving microclimates. Grassl suggests alternatives like gravel surfaces in beer gardens or grass pavers in parking lots, which reduce heat effects and promote biodiversity compared to traditional asphalt – and are more cost-effective.
3 – Use High Albedo Surfaces
In addition to more green spaces, light, reflective materials counteract the heat in cities. These can reduce excessive heat radiation on hot days. In urban planning, this is known as the ‘albedo effect’.
The albedo effect has particularly positive results in densely built-up areas with large roof areas. Light concrete surfaces, paving made of concrete or natural stone or gravel-bound ceilings are best suited. A combination of rough surfaces, porous materials and lighter colours in the paving also ensures a lower surface temperature and a higher thermal storage capacity.
4 – Employ Low-Energy Cooling Solutions
Avoid exacerbating the heat island effect with air conditioning systems. Grassl advocates for low-tech building solutions that use thermal mass to cool buildings naturally during the night, reducing energy consumption and improving sustainability.
“In future developments, even energy-saving and sustainable buildings will have to be renovated due to climate change,” he adds.
5 – Build Higher to Prevent Overheating
Tall buildings can provide shading and create air currents that enhance neighbourhood ventilation. They contribute positively to urban cooling strategies when designed with reduced glass surface areas and integrated natural landscape elements.
“High-rise buildings shade each other,” says Grassl. “For this to work, the window area must not exceed 40%. Glass palaces are expensive in terms of energy consumption, both in summer and winter, because glass offers poor insulation.”
Climate Interconnectedness
According to Gregor Grassl, climate protection and climate adaptation are two inseparable dimensions of the climate crisis and should not be played off against each other.
As he notes, heat stress in urban areas is a major challenge for the present and the future, but it also offers an opportunity to make our cities more liveable, sustainable and resilient.
