The Infrastructure Challenge Behind Urban Heat: Why Cities Need a New Approach to Heating and Cooling

Last month, the Climate Change Committee (CCC) published one of its starkest assessments yet of the UK's preparedness for a changing climate.

Among its conclusions was a warning that around nine in ten UK homes could face overheating risks by 2050. Heatwaves exceeding 40°C may become commonplace across all parts of the country, potentially contributing to an additional 10,000 heat-related deaths each year. Cooling, the report argues, is becoming a matter of public health and national resilience.

For a country that has historically focused far more attention on keeping buildings warm, the implications are profound.

The CCC's recommends that air conditioning should be installed in all hospitals and care homes within the next decade, and in all schools within the next 25 years.  

Offices, universities and residential developments will also face growing cooling demands – and much of this challenge will play out within the buildings and districts that already exist today. Industry estimates suggest that around 80% of the buildings expected to be occupied in 2050 have already been built. The future of urban heat will therefore depend as much on retrofit and adaptation as it does on new development.

That raises a question which receives surprisingly little attention.

Where will all that cooling actually come from?

At first glance, the answer appears straightforward. Buildings install cooling systems in much the same way they install heating systems today. Yet the more closely the challenge is examined, the more complicated it becomes.

A modern city centre concentrates people, activity and energy demand. Residential towers, offices, commercial zones will all require cooling – and heating.

The challenge is finding space for the infrastructure required to deliver it. Rooftops already compete with solar PV, biodiversity requirements, amenity space and other building services. Plant rooms consume valuable floor area, while planning and acoustic constraints further narrow the available options.

As cities become denser, the question becomes less about how individual buildings provide heating and cooling and more about how thermal energy is managed across entire districts.

A Challenge Cities Have Faced Before

Interestingly, this is not a new problem.

The idea that thermal energy can be shared across communities is one of the oldest forms of energy infrastructure in Europe.  

In Chaudes-Aigues, France, geothermal water was being distributed through a network of wooden and stone pipes as early as the 14th century. Residents paid for access to shared heat infrastructure maintained by the local authority, creating one of the earliest known examples of district heating anywhere in the world.  

More than six centuries later, European cities are once again exploring how thermal energy can be shared, stored and reused more effectively.

In Salaspils, Latvia, where winter temperatures regularly fall below -15°C, the local district heating system has undergone a remarkable transformation. Since 2018, the share of renewable energy within the network has increased from 56% to 94%, while heating-related emissions have fallen by 88%. The next phase includes heat pumps supplied by waste heat recovered from data centres.

Paris-Saclay offers another example. The district heating and cooling network serving the innovation district draws geothermal energy from an aquifer approximately 700 metres below ground. Water at around 28°C is upgraded by heat pumps before being distributed across the development. By 2027, the network is expected to serve more than two million square metres of floor space while sourcing the majority of its energy from renewable and recovered sources.

Neither project was developed around a single technology, but around a broader question: how can cities move thermal energy more intelligently?

Rethinking How Thermal Energy Moves

That same question is beginning to emerge across the UK.

Earlier this month, Arup and Ordnance Survey announced a major update to the national heat network zoning model being developed on behalf of the Department for Energy Security and Net Zero. The model will support at least ten English towns and cities as they begin establishing heat network zones, with further locations expected to follow.

The government's ambition is significant. Under the Warm Homes Plan, heat networks are expected to supply 7% of UK heat demand by 2035, more than doubling their current contribution, with a longer-term ambition of around 20% by 2050. Mandatory heat network zoning is expected to begin later this year.

While heat networks represent only one part of the future energy mix, the programme reflects a broader shift in thinking. Heating and cooling are being planned at district and city scale rather than solely at the level of individual buildings.

This is where the ground starts to become particularly interesting.

Why the Ground Matters

Ground source heat pump systems are often discussed in terms of efficiency, carbon reduction or operating performance. Those benefits are important, but they do not fully explain their growing relevance within dense urban developments.

The ground provides something that cities need: the ability to store, move and reuse thermal energy.

And one of the most distinctive characteristics of ground-coupled systems is their ability to support both heating and cooling within the same infrastructure.

Rather than simply rejecting excess heat, ground-coupled systems can store, share and reuse thermal energy, creating opportunities to balance heating and cooling demands across buildings and seasons. The principle sits at the heart of many emerging shared ground loops and ambient heating and cooling networks, where buildings can simultaneously consume and contribute thermal energy depending on their needs.

Underpinning this approach are the stable temperatures found below the surface. The ground can act as a thermal source in winter and a thermal sink in summer, helping turn excess heat into a resource rather than a by-product.

And that flexibility may prove just as valuable as the efficiency gains traditionally associated with ground source heat pumps.

Ground infrastructure can also help reduce pressure on some of the most commercially valuable parts of a development. Rooftop space, visible plant locations and internal plant areas frequently compete with other project priorities.

At 52 Avenue Road in central London, for example, shared ground source infrastructure was integrated within a high-specification, heritage-sensitive development, supporting long-term low-carbon heating while accommodating the demands of an ultra-prime residential scheme.

Of course, no two sites are the same.

Ground conditions, existing utilities, drilling access, planning constraints, heating and cooling loads all influence what is possible on a site. Understanding those factors early allows project teams to make informed decisions before key aspects of the design become fixed.  

A New Layer of City Infrastructure for the 21st Century

Cities have always evolved by adding new layers of infrastructure.

Water networks transformed public health. Electricity transformed buildings and industry. Telecommunications transformed how cities communicate and operate.

A hotter, denser and increasingly electrified future will require a similar shift in how we think about thermal energy.

The examples emerging across Europe, alongside the UK's move towards heat network zoning, show that waste heat, geothermal resources and shared thermal infrastructure are moving from niche considerations towards mainstream infrastructure planning.

As cooling demand grows, electricity networks come under greater pressure and urban developments become more constrained, thermal infrastructure will be judged not only on efficiency, but on resilience, flexibility and long-term performance.

The UK has spent decades discussing how buildings consume energy.

The next phase of the conversation may be about how cities move it.

As heat network zoning, urban cooling and shared thermal infrastructure continue to evolve, staying close to the conversation matters. Subscribe to The Source for the latest insights, project updates and industry developments from the Genius Energy Lab team.  

‍