[Heat Wave 2026] Cooling Ladder 2.0: It's Time to Cool Cities Before Buildings

The recent European heat wave should force Belgium to ask a harder question: Are our buildings and cities designed to protect people from heat, or only to pass a calculation?

Last week, I gave five interviews to news outlets across Wallonia. Most questions focused on the Belgian EPBD overheating indicator: Is the calculator accurate? Does it capture future overheating risk? Should the method be revised?

Yes, it should. But Belgium’s problem is not only an EPBD calculation problem. It is a climate policy problem. It is a social justice problem. It is a strategic financing problem. And it is an urban planning problem.

We cannot continue to discuss overheating only at the scale of individual buildings. Regional weather forecasts and building regulations cannot fully capture the microclimatic conditions experienced inside cities, where solar radiation, urban geometry, heat storage in materials, limited vegetation, and the urban heat island substantially increase thermal stress.

As a consultant, I have seen this happen repeatedly. A school receives funding for two air-conditioned classrooms, but not for external shading. Another buys portable air conditioners but has no mechanical ventilation. Another replaces windows while leaving the façade exposed to the afternoon sun. Every project solves one symptom, but none solves the problem. This is a classic example of maladaptation: fragmented funding leading to fragmented solutions, instead of one integrated strategy that addresses the root causes of overheating.

This is why I now plead for a Cooling Ladder 2.0. The original Cooling Ladder is rooted in the sustainable cooling hierarchy: reduce cooling demand first, use passive cooling, then efficient systems, and only then active cooling. The framework was developed by the Dutch Climate Adaptation Platform OSKA and recently promoted at the European level by ES-SO. European Solar Shading Organisation ES-SO, Peter Winters, Yves Lambert and Ann Van Eycken. This logic is consistent with the work of researchers such as Mattheos Santamouris on passive and active cooling for the built environment and with the European Environment Agency’s call to prioritize passive cooling strategies. But the first step of the ladder must now be upgraded:

Step 0: Cool the city. Before cooling buildings, we must cool the urban environment through trees, shaded streets, parks, permeable surfaces, cool roofs, cool pavements, water, urban ventilation corridors, and climate-sensitive planning. Then we can cool buildings properly:

1. Avoid heat gains. Limit excessive window-to-wall ratios, especially on east and west façades. Use external shading, vegetation, reflective roofs, appropriate glazing, and better envelope design.

2. Remove heat passively. Use cross ventilation, night cooling, thermal mass, shaded courtyards, and safe operable windows.

3. Use efficient systems. Ceiling fans, smart controls, reversible heat pumps, and efficient cooling should support good design, not compensate for bad design.

4. Install active cooling where health and safety require it. Hospitals, nursing homes, schools, childcare centers, emergency facilities, and social housing must be able to maintain safe indoor temperatures during heat waves. Air conditioning everywhere would be irresponsible. But refusing active cooling in sensitive buildings is also irresponsible.

France is now openly debating whether air conditioning remains taboo during heat waves. Belgium should have had this debate a decade ago. We also need to speak about inequality.

Belgium has large disparities in housing quality, wealth, and climate protection. Lower-income households are more exposed to poor housing and energy vulnerability, while wealthier households are often better protected through ownership, better locations, larger dwellings, private gardens, insulation, shading, and the ability to buy comfort. Belgian wealth is also strongly shaped by housing assets and ownership patterns. (NBB)

Yet the environmental and adaptation costs are not fairly distributed. Wealthy households are rarely forced to reduce oversized glazing, renovate poor-performing homes, limit cooling demand, or pay the full environmental cost of their comfort choices. The people least responsible for climate emissions are often the first to suffer from overheating.

Next month, Sciensano’s Be-MOMO surveillance will help us understand the mortality impact of this heat episode in Belgium. Be-MOMO monitors all-cause mortality and can detect unusual excess mortality related to extreme weather or environmental conditions. We do not yet know the final number, but we already know that overheating is not only a comfort issue. It is a public health issue. (sciensano.be)

I see the same problem in education. In my Sustainable Building Design courses, students understand the Cooling Ladder and apply it well. But when they move into other design studios, the conversation often shifts back toward form, aesthetics, spatial experience, and iconic façades. Climate-responsive design becomes secondary instead of becoming the foundation of architecture. This is not a criticism of students. It is a warning about our professional culture. If cooling is discussed only after the city is planned and the building is designed, we have already failed. Belgium needs a coherent climate adaptation policy for the built environment. Not emergency advice during heat waves. Not only better EPBD calculators. Not air conditioning everywhere. But a clear hierarchy:

1. Cool the city., 2. Reduce heat gains., 3. Design passive resilience., 4. Use efficient systems., 5. Actively cool sensitive buildings where health and safety require it.

That is the Cooling Ladder 2.0.

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