Heat is no longer an exceptional phenomenon, but a dominant parameter in the design of our cities. Anyone planning open spaces needs to know today: The next summer is sure to come – and with it the question of how we can ensure urban quality of life in times of overheating. It’s time for heat to finally be taken seriously as a key design parameter in open space competitions. Because the city of tomorrow will not only be built, it will be cooled, shaded and – cleverly designed – become an oasis against climate stress.

• Why heat is now a decisive factor in open space competitions
• The most important urban climate principles that every planner needs to know
• Innovative strategies for heat reduction through design, choice of materials and vegetation
• How competition procedures can systematically demand and promote heat integration
• Practical examples from Germany, Austria and Switzerland that serve as role models
• Legal and planning framework conditions for dealing with heat
• Tools, simulations and evaluation procedures for heat-adapted designs
• Opportunities, risks and challenges – from acceptance to maintenance
• Why heat protection is more than just shade and misting

Heat stress as the urban norm – a paradigm shift in open space design

The urban reality of Central Europe has changed fundamentally in recent years. Where summer heat used to be considered a temporary nuisance, cities are now experiencing temperature peaks that not only affect the quality of life but also threaten the health of the population. Germany, Austria and Switzerland are experiencing record levels: Nights in which the thermometer does not fall below 25 degrees are no longer a rarity in city centers. The heatwaves of 2003, 2019 and 2022 were by no means the last – and they hit densely built-up districts in particular, where sealing and a lack of vegetation massively increase the urban heat island effect.

What does this mean for planning? Heat is no longer a “nice-to-have” issue, but a must. Anyone entering competitions for parks, squares or schoolyards today is confronted with the question: How can the open space be designed so that it is still suitable as a place to spend time even at 38 degrees? The days when a few trees on a site plan could be used as heat protection are over. The demands on designs are increasing rapidly because users, politicians and administrators are increasingly realizing that any open space planning must also provide an answer to climate change.

The causes of heat stress are complex. In addition to global warming, local factors play a prominent role: dense buildings, dark materials, a lack of evaporation areas and the decline in green structures are major contributors to cities heating up and barely cooling down at night. As a result, heat stress is becoming a permanent condition, with serious consequences for vulnerable groups such as children, the elderly and people with pre-existing conditions.

For planners, this means a paradigm shift. It is no longer enough to deliver pretty pictures in the competition. What is needed are resilient concepts that systematically address the issue of heat – from analysis and strategy to detailed training. This requires a new self-image: designing today also means creating resilience to the climate. Anyone who ignores this is failing to plan for reality.

But how can heat be assessed in competitions? Where are the greatest levers for heat-compatible design? And how can the focus on climate adaptation be reconciled with other objectives such as quality of stay, biodiversity and social participation? These are questions that pose new challenges not only for planning offices, but also for awarding authorities and juries.

The key finding: heat is no longer a subordinate criterion, but a design parameter on a par with aesthetics, functionality and cost-effectiveness. Anyone planning open spaces today must know how their own work influences the microclimate – and be prepared to take responsibility for it.

Urban climate basics – why every degree counts

Anyone concerned with heat as a design parameter cannot ignore the fundamentals of urban climate. The urban climate is the result of a complex interplay between buildings, materials, vegetation, bodies of water and meteorological factors. The urban heat island effect is particularly relevant: due to their dense structure and high level of sealing, cities store enormous amounts of heat during the day, which they only slowly release again at night. The temperature difference between the city and the surrounding area can be up to 10 degrees in hot phases – a value that is anything but trivial for the well-being and health of residents.

The phenomenon of tropical nights, when the temperature does not drop below 20 degrees, is a direct result of these effects. Inner cities, districts with little greenery and areas characterized by tall buildings and narrow streets are particularly affected. This creates a dangerous mixture of heat build-up, lack of ventilation and insufficient shade. Anyone who has ever experienced how an asphalted square heats up under the midday sun knows that without targeted countermeasures, the open space becomes an oven.

Scientific studies show that even a moderate increase in vegetation density has a significant effect on the microclimate. Trees, shrubs and green facades cool not only through shading, but above all through evaporation. This so-called evapotranspiration effect measurably lowers the ambient temperature – up to 3 degrees are possible in green areas. Water surfaces and open ground structures, which also promote evaporation and thus ensure pleasant temperatures, have an even greater effect.

Materiality plays another key role. Dark, dense surfaces store heat particularly effectively, while light, reflective materials and porous coverings reduce heating. The design of open spaces also influences the urban climate: wide street profiles, low buildings and open squares promote ventilation, while narrow courtyard structures and high perimeter buildings inhibit the exchange of air.

For competitions, this means that without in-depth knowledge of the urban climate, any design strategy will come to nothing. Not only a feeling for the location is needed, but also an understanding of climate simulations, bioclimate maps and the effect of different measures on the microclimate. Only then can heat be specifically integrated as a parameter in the design – right from the start, not as an afterthought.

Anyone planning open spaces for the 21st century today must take every degree seriously. Because the difference between pleasant city life and unbearable heat stress is decided in detail – and in the competition for the best ideas.

Creative strategies against the heat – from vision to concrete measures

The good news is that the toolbox for heat-adapted open space design is full to bursting. It’s no longer just about the number of trees, but about a clever interplay of vegetation, water, materiality and spatial structure. Those who take heat seriously as a design parameter develop multifunctional solutions that improve the microclimate and at the same time increase the quality of stay.

One of the most effective approaches is targeted shading. Trees are still the champions here: they not only provide shade, but also cool through evaporation and contribute to air purification. However, the right choice of species, site suitability and long-term maintenance are crucial. Urban-proven heat tolerance, sufficient root space and an easy-care structure are just as important as the arrangement – linear avenues, dense groups or specific individual positions each create different microclimates.

Water plays an increasingly central role. Open water surfaces, fountains, mist jets or – particularly clever – water-permeable coverings with integrated water storage provide evaporative cooling and offer children and adults alike a welcome way to cool off. The integration of rainwater management into the open space design creates additional synergies: infiltration areas, swales, infiltration trenches or retention areas buffer heavy rainfall and improve the microclimate at the same time.

The choice of materials also makes a difference. Light-colored, reflective surfaces reduce heating, while porous, green or partially unsealed surfaces promote the water balance and evaporation. Innovative solutions such as cooling paving stones, green seating or mobile shade providers open up new horizons. It is important that these measures are not seen as individual actions, but as part of a holistic concept that takes into account the specific conditions of the location.

The design of the spatial structure has a decisive influence on how heat is experienced. Open, ventilated spaces, small-scale structures with green retreats, flexible uses and adaptive elements such as temporary shading systems make the difference between heat hell and a favorite place. In competitions in particular, it is worth proposing bold and experimental solutions – such as modular greening systems, seasonal water installations or participative elements that actively involve users.

Finally, maintenance and development should not be forgotten. Heat-adapted design is not a one-off event, but a process. Only if the measures are maintained and further developed in the long term will the open space remain liveable in the future. This requires close interaction between planning, operation and users – and a new culture of cooperation between all those involved.

Integrating heat into the competition process – from the competition brief to the jury’s decision

Dealing with heat as a design parameter does not begin with the design, but with the competition brief. Competition procedures that systematically address the issue create the basis for innovative solutions and ensure the quality of the results. This begins with a precise brief: What urban climate challenges are to be expected? What requirements result from climate analyses, heat maps or local experience? The clearer the specifications, the more targeted planners can develop their concepts.

Binding evaluation criteria play an important role. Are heat reduction measures explicitly required and weighted? Are there minimum standards for shading, evaporation or ventilation? Is the long-term development of the microclimate taken into account? Competitions that make such criteria transparent not only promote the quality of the designs, but also the comparability and comprehensibility of the jury’s decision.

Climate simulations and evaluation tools are increasingly being used to analyze the impact of designs on the microclimate at an early stage. Tools such as ENVI-met, urban climate maps or thermal comfort simulations provide valuable data – provided they are interpreted by experts and integrated into the planning process. The involvement of climate experts in the jury is also increasingly becoming the standard in order to ensure a professional assessment.

Involving users and the public can help to increase the acceptance of heat-adapted measures. Participatory elements – such as citizen workshops, feedback rounds or temporary test installations – make the effect of shading, water or greening directly tangible and create a common understanding of the need for heat protection. Especially in densely populated neighborhoods, such approaches can help to defuse conflicts and develop viable solutions.

Finally, communication is also crucial. Competitions that communicate the importance of heat protection clearly and comprehensibly set an example – not only for the planning offices, but also for politicians, administrators and the public. They make it clear that heat is not someone else’s problem, but a central design task that can only be solved together. Those who ignore this risk not only poor planning, but also a long-term loss of quality of life.

The integration of heat as a design parameter in the competition process is therefore more than just a technical challenge. It is an expression of a new understanding of planning that sees climate change as a starting point and not as a side note. Those who take bold action here will shape the open spaces of tomorrow – resilient, liveable and sustainable.

Practice, perspectives and challenges – what really counts

Successful examples from Germany, Austria and Switzerland show that the integration of heat as a design parameter is not a pipe dream, but a feasible reality. The new city park in Vienna-Favoriten, the redesign of Munich’s Elisabethmarkt and Zurich’s Turbinenplatz set standards for a combination of shading, evaporation and innovative choice of materials. They show how competitions can be specifically geared towards microclimate, quality of stay and social usability – and still create distinctive places.

At the same time, planners are facing considerable challenges. Uncertainty about future climate scenarios makes long-term forecasts difficult, while tight budgets, differing interests and often contradictory requirements for land use, nature conservation and infrastructure make implementation more difficult. Added to this is the balancing act between short-term attractiveness and long-term climate resilience: what is considered a cool design element today can be high-maintenance or even counterproductive tomorrow if it is not well thought out.

A key risk is the tendency towards symbolic politics. A few additional trees, a spray mist feature or fancy awnings are not enough to achieve real heat reduction. What is crucial is a systematic approach: a well-founded analysis, a consistent strategy and the willingness to take uncomfortable measures – such as removing parking spaces or redistributing land in favor of greenery and water – are needed.

The legal and planning framework conditions continue to evolve. Municipal climate adaptation concepts, funding programs and new urban land-use planning instruments create leeway, but also place new demands on documentation and verification. Planning offices are required to continuously expand their expertise in the areas of urban climate, simulation and monitoring – and to actively participate in the development of new assessment standards.

In the long term, open space planning faces a dual task: it must react to the increasing heat in the short term and at the same time create structures that will still function in 30 years’ time. This requires the courage to innovate, an open culture of error and a willingness to learn from pilot projects. Because one thing is clear: the heat problem will not disappear. But it can be managed – creatively, intelligently and in the best sense of the word.

What ultimately counts is the added value for people: Open spaces that offer quality of life even on hot days, protect health and enable social encounters. Those who see heat as a design parameter are not planning against climate change, but with it – and turning the city into a stage for a future worth living in.

Conclusion – heat as an opportunity for a new planning culture

Heat is more than just an annoying side issue. It is the litmus test for the future viability of open space planning. Anyone who takes heat seriously as a design parameter in competitions assumes responsibility for quality of life, health and urban resilience. This requires new skills, creative solutions and the courage to question the tried and tested. The tools are there, the examples are available – now the task is to disseminate the findings and implement them consistently.

The open space competitions of tomorrow will no longer be decided solely on beauty and functionality, but also on how well they deal with the challenges of overheating. This is not a restriction, but an invitation to innovation and excellence. Those who ask the right questions now, develop the best strategies and seek dialog with users, administration and politics can not only make the city cooler, but also more liveable, fairer and more future-proof.

In the end, heat is not an opponent, but a catalyst for a new planning culture. The city of the future will not be built, it will be designed – with a cool head, creative ideas and a willingness to take responsibility. Garten und Landschaft remains your guide on this path: professional, critical, inspiring. Because nowhere else will you find such concentrated expertise and so much passion for the open space design of tomorrow.