The Evaporative City Bioclimatic adaptation and regeneration using water

The present extended abstract highlights preliminary steps of an ongoing industrial doctoral thesis, developed in the context of a European Commission’s Horizon 2020 innovation programme (SOLOCLIM-EU) conducted in partnership with the industry, which aims to educate, supervise, and train six Early-Stage Researchers (ESRs) on generating microclimate solutions that can respond to urban overheating1 in outdoor environments throughout a Ph.D. Program developed inside an industrial setting. The programme is divided into three work packages (WP): Vegetation (WP-1), Water (WP-2), and Responsive Systems (WP-3). The solutions within each cluster are examined at two scales: the streetscape, i.e., the interface of buildings and their outdoor environment, and the larger scale of the urban block, neighborhood, and city-scale. The principal methodology of all three WPs is “Research Through Design” (RTD) supported by rigorous analysis as appropriate for the different scales (such as microclimate simulation software, geoprocessing using satellite images, and spatial analysis using GIS software). The Thesis titled “The Evaporative City: Bioclimatic Urban Regeneration Through Water” is part of the WP-2 “big scale” and seeks to define strategic urban water use guidelines that can help alleviate the heat stress in neighborhoods located in different European climate regions.

Designs and plans delivered now by design, planning, and engineering need to incorporate a microclimate sensitive approach that can respond to shifting extremes (too hot, too cold, too dry, and too wet). However, apart from the need for new solutions, the industry currently lacks expertise. On the academic side, some of this body of knowledge is also lacking research. The use of vegetation in cities, for example, is well known to reduce the Urban Heat Island (UHI) effect. Still, there are remaining questions about the proper allocation of green in cities to have an optimal effect. Little is also known about the efficacy of water-based interventions to the urban microclimate such as misting systems, evaporative cooling of facades, sprays, fountains, water walls, etc., in relation to the surrounding urban fabric and when applied broadly in the city. 2 3 4 These interventions also have social and urban ecological co-benefits such as stormwater infiltration and storage and provide a respite to citizens during heatwave events—instantly generating space liveability.

Besides being a powerful tool for transforming urban spaces in new commons and its role in promoting the “Right to the city,” as proposed by David Harvey (2008), water has several advantages as a natural cooling technique. The two main effects are the high thermal mass of water and evaporative cooling, due to the evaporation process. A lot of energy is needed to convert liquid water to vapor, and this energy comes from the water and surrounding air, resulting in cooler air and water. Regarding cooling principles and physics, urban water cooling can be divided into three main groups: ponds or water bodies (P), fountains, sprays, jets (F), and misting or fog systems (M). The way citizens interact with urban waters and thus experience such principles can be divided into nine verbs: to swim (on), to perform (on), to transit (through), to shelter (in), to sightsee (to go see and be seen), to manage (store, infiltrate, conduct), to play (with), to listen and to contemplate. In Figure 1, nine contemporary design projects were linked to “water interactions” and to “water cooling principles.” These projects constitute the preliminary steps in the research and one of its products: a catalogue of references containing a description of the project and the microclimate benefits provided by the water cooling features. The situation before and after the intervention is simulated using ENVI-met software to estimate gains in thermal comfort such as air temperature decrease, mean radiant temperature, and wind speed. An example of the Grotestraat in Nijverdal-NL, an intervention project from Dutch Landscape office OKRA Architects is highlighted in Figure 3. This project puts together rain gardens, bioswales, fountains, and splashes. Fountains are remarkable elements in several cultures and carry enormous symbologies. Nowadays they became key elements to urban revitalization because can at the same time engage citizens and provide respite during heatwaves. The way they are now conceptualized is key to achieving a more sustainable urban water management. The new Grotestraat addresses both heat and flooding.

The Grotestraat is almost unique because there’s a gap of cases that purposefully addresses multiple instances. The announced climate crisis upon us is widely advertised but is surprising how little the design discipline, and especially the design of cities, devotes to thinking about the way architecture interacts and influences climatic processes.5 The issue seems to be two-fold: technical and scalar. First, thermal and microclimate analysis demand specific knowledge and software that is out of reach to most architects. Second, it requires to be seen in multiple scales. The Urban Heat Island, for example, is expressive in the city scale, but to address it, solutions happen in the very small scale of buildings and squares and need to resolve not only environmental concerns but also livability, disuse, and equality. A view from the city allows to identify of local hot spots, as Sofia Dona poses in the text “Moving from the Macro to the Microscale in the Anthropocene6,” the UHI problem is not enough faced from the small scale, spaces must be also integrated into a network of medium and large-scale green corridors to generate continuous masses of plants, pedestrians, and breezes, to be more effective physically and collectively.

With the goal to generate a design decision support system (DDSS) regarding urban planning, design, and policy guidelines for implementation of the water systems in the masterplan scale, or the neighborhood, the thesis was divided into four main parts: the Block, the City, the Neighborhood and Guidelines. In the Block scale, several ENVI-met simulations are performed in ‘test-bed’ blocks selected from urban morphometric analysis for European cities in three different climate zones (Milan, which has hot Mediterranean summers, Rotterdam, with cold oceanic summer and Madrid, located in arid hot summer climate). Data such as temperature, humidity, and wind speed are also collected on the field with a mini mobile station to gain insights into the human scale of the “testbed” blocks. In the City scale, morphometric analysis using momepy Python script7 is combined with GIS spatial analysis and heat and flooding vulnerabilities to gather insights into water-cooling aptness in these cities (see Figure 2 maps for Nijverdal as reference for studies in the City scale). Results from Block and City together inform the Neighbourhood study: quantitative results are used to test and simulate toolkits of solutions in this scale, that are re-assessed together with a group of experts in an iterative design process (RTD). Lastly, Figure 3 also brings the question of different cultural relationships communities might have with water by placing together a small-town project in the Netherlands and one in northern Italy.