To achieve optimal results, the adaptation measures are implemented simultaneously on three scales: 1) city-wide, 2) local and 3) the individual person. The implementation of the adaptation measures described here just started or have been planned. Full implementation and city-wide results will take a long time and are only expected to be completed by 2030.
The construction of buildings in the city of Antwerp is regulated by a building code, which all inhabitants and developers need to adhere to when renovating or constructing a building. In this code, specific instructions were added (9/10/2014) to help reducing heat stress in the city over time:
- For all new or renovated roofs with a slope of less than 15% and a surface area of more than 20m², it is compulsory to install a green roof on top. This drastically lowers the temperature of the roof and cools air temperature by retaining and evapo-transpiring rain water. Additionally, green roofs provide extra thermal isolation for the building reducing the need for heating and cooling.
- All new installed private gardens and open parking lots need to be green and permeable. Only 20m² can be paved in gardens <60m² and only 1/3 in gardens >60m². All outdoor private parking lots need to have a permeable grassed surface.
- The majority of the buildings in the city centre have historical plaster facades. When renovated, these building fronts need to be painted in the original light, preferably white colour. White buildings reflect more sunlight and will not warm up as easily as dark buildings, thereby reducing the heat radiation from these buildings.
Regularly, large squares, parks and neighbourhoods in the city are renovated. During the planning phase, the city administration included the optimisation of the thermal comfort situation as a new factor to be considered. To enable targeting actions, detailed information is needed on the local microclimate. Advised by VITO, the city of Antwerp has decided to use the Wet Bulb Globe Temperature (WBGT) indicator when assessing and optimizing the heat stress impact of renovation plans. WBGT, in contrast to simple temperature measurements, takes into account the radiation load (both shortwave and longwave), humidity and wind speed, which all influence human thermal comfort. Several detailed (1m resolution) modelling studies were performed by VITO to quantify the local WBGT values and assess the potential impact of planned adaptation measures. This led to the inclusion of green-blue infrastructure measures (e.g. trees, permeable surfaces, water ponds, fountains) in renovation plans.
The modelling was complemented by a citizen science measurement campaign during the summer of 2018 in the framework of the H2020 Ground Truth 2.0 project. About 20 residents of Sint-Andries neighbourhood were engaged in measuring the WBGT in various types of locations. Besides validation of the model results, this campaign raised awareness of the heat stress problem and stimulated a discussion about the possible adaptation measures.
In Belgium, ‘heat health action plans’ are triggered based on temperature forecasts in rural settings. This leads to underestimation of heat stress in cities like Antwerp, where a considerable urban heat island effect causes twice as many heat wave days in urban areas than in the rural surroundings. In order to provide more accurate heat stress forecast for Antwerp, a short-term (5 day) heat forecast system, based on a combination of the regular European forecast model by ECMWF and the UrbClim model, was set up by VITO. The system delivers a forecast for each neighbourhood of Antwerp, taking into account the urban heat island effect. This allows efficient deploying of aid resources, targeting mostly the vulnerable elderly and children, to the places where they are needed most. Furthermore, a web platform was developed by the city of Antwerp to issue heatwave warnings to health aid workers and other relevant stakeholders, including advice what to do in case of a heatwave. The system is active during the warm months of the year in Belgium (April-September) and is managed by the city administration.