Warwick experts react to the tolls UK Heatwaves are having on infrastructure
Professor Xueyu Geng, Professor in Geotechnical Engineering and Dr Reyes Garcia, Associate Professor in Structural Engineering, from the School of Engineering respond to questions on how our buildings and transport networks cope with heat?
How do buildings and transport networks cope with heat?
Professor Xueyu Geng said: "When temperatures rise this sharply, and for this long, the effects ripple across everything we have built, our homes, our offices, our railways, our roads, the very ground beneath them. Buildings struggle to expel heat they were designed to retain, and cooling systems are pushed beyond their capacity. And beneath the surface, in the soils and earthworks that carry our transport networks, changes are happening that are invisible to the naked eye but deeply significant to those of us who study them.
"The rails that expand and buckle in the sun. The road surfaces that soften under tyre loads. And perhaps most critically, the earthwork embankments and slopes that have carried our trains and traffic for generations, and whose stability depends on a delicate balance of soil moisture, root systems and ground pressure that prolonged heat quietly but significantly disrupts.
"Railway track buckling. Steel rail expands significantly in extreme heat: a 1°C rise in temperature causes roughly 11mm of expansion per kilometre of track. Rail is installed with a 'stress-free' temperature in mind, and when ambient and solar-radiation temperatures exceed that threshold, the track can buckle laterally, what the industry calls a 'sun kink'. This is why speed restrictions are imposed on the network during heatwaves; it is not a precaution, it is a structural necessity.
"Road surface degradation. Sustained high temperatures soften bituminous asphalt surfaces, leading to rutting, shoving, and, very visibly, tyre-contact marks at junctions and bus stops where vehicles sit under braking load. These are not cosmetic issues; deformed surfaces affect drainage, vehicle handling, and the long-term structural integrity of the carriageway.
"Embankment stability. Perhaps the least visible but equally serious risk relates to the earthwork embankments, the engineered soil structures that carry railways and roads across the UK's landscape. In normal UK conditions, vegetated embankment slopes benefit from what geotechnical engineers call 'unsaturated soil suction’, a negative pore water pressure that gives soil additional strength beyond its basic material properties. Plant root systems reinforce this further, binding the soil and drawing moisture through transpiration. Prolonged extreme heat disrupts both. As soil desiccates, it shrinks and surface cracking develops. Vegetation under heat stress dies back and loses its root tension. The embankment becomes, in engineering terms, progressively weaker, quietly, and without any visible warning sign at the surface. The critical moment comes when intense rainfall follows: severely desiccated, cracked soil does not absorb water efficiently. Water runs off the hardened surface, dramatically increasing erosion, while water entering the crack network can reach depth rapidly, creating sudden and significant changes in the stress state of the embankment, exactly the conditions that precede slope instability."
Are there any specifics related to this forecast heatwave that present engineering challenges?
Professor Xueyu Geng continues:"This week's heatwave brings all of these risks into sharp focus simultaneously. The Met Office has forecast peak temperatures of 38°C in southern England, potentially breaking the UK's June record, with overnight temperatures remaining above 20°C, what forecasters call 'tropical nights'. Perhaps most striking is the humidity: dew points forecast at around 22°C this week, compared to single figures during the record-breaking 2022 heatwave. And critically, this is not a single hot day, it is a sustained, multi-day event, with thunderstorms and intense rainfall forecast to follow as the heat breaks down.
"From a ground engineering perspective, every one of these factors matters, and they matter not just for managing today's emergency, but across the entire lifecycle of infrastructure, from initial design through to long-term maintenance. Temperature, humidity, duration, and the pattern of heat followed by intense rainfall are not just weather statistics; they are the conditions that determine how soils behave, how slopes perform, and how earthworks age. What makes this moment particularly important is that we now have decades of climate data that allow us to understand these patterns and, increasingly, to predict what is coming. The challenge is knowing what to do with that knowledge, especially for infrastructure that was built long before we understood what today's climate would look like. Modifying or retrofitting existing earthworks, embankments and transport structures is far more complex and constrained than designing new ones from scratch. Existing assets have fixed geometries, live operational pressures, and physical limitations that make adaptation genuinely difficult. Yet that is precisely the challenge we must face, because the infrastructure that Britain built first, and that has served us longest, is also the infrastructure most exposed to a climate it was never designed for."
What are ways we can keep our homes cool?
Dr Reyes Garcia adds: "As temperatures continue to climb during heatwaves, British homes are increasingly feeling like ovens. The secret to surviving future summers lies in rethinking how our homes are built and insulated all year around. We have to shift our focus from simply winter warming to summer cooling as well, so we can design homes that naturally resist heat waves.
"Two ways modern engineering can keep our homes cool:
"1. Traditional walls made of solid bricks or concrete blocks act like sponges, absorbing heavy heat from the afternoon sun and slowly “baking” the inside of a home. A few years ago we designed a prefabricated wall specifically engineered to fight severe heat in tropical and warming climates. This new wall was designed as a layered “sandwich” structure using recycled aggregate concrete, expanded polystyrene and cement boards. This unique combination disrupts the path of heat. Heat cannot travel easily through the foam-and-air layers, so the walls act as a thermal shield. We did some laboratory testing and also built a full scale house, and we showed that the wall can reduce internal wall surface temperatures by up to 5°C compared to standard brick-and-mortar walls. This can make a huge difference in terms of comfort and electricity (mainly fans and AC) use, and eventually costs: https://doi.org/10.1016/j.conbuildmat.2024.135568
"2. We also normally think of insulation as a “duvet” to keep us warm in the winter, but it works just as well the other way around! High-quality insulation acts as a shield, blocking the hot afternoon sun from heating our houses. We are using Phase Change Materials (PCMs) as a thin “duvet” plastering, which effectively acts like microscopic built-in ice packs in walls. PCMs are blended directly into plasterboard (or ceilings) and so when the house gets too warm during the day, these materials melt at a microscopic level, absorbing the excess heat and keeping the room at a comfortable temperature. At night, when the outside air cools down, the PCMs solidify again, releasing the trapped heat safely when it is cool enough to open the windows. It is a completely automatic and cost-effective way to avoid extreme indoor temperatures. In our experiments we have observed that PCMs can reduce indoor temperatures by about 1-3°C: 10.1016/j.jobe.2023.108315
"By using better and cost-effective smart materials that block and/or absorb heat, we can keep British homes comfortable, sustainable and cool for years to come."