6 May 2025
Cameron McLaren, Senior Climate Consultant, Longevity Partners
An Unlikely Collision: Pandemic Meets Heatwave
In the summer of 2020, as London sat eerily still beneath the constraints of the first major COVID-19 lockdown, an unexpected and record-breaking heatwave swept across the city. The streets were deserted, public transport ran nearly empty, and for the first time in modern history, most of London’s commercial office spaces stood vacant for months. But while people hunkered down indoors, working remotely and weathering the pandemic, the capital’s skyline of glass and steel faced an entirely different crisis, one it was never designed to handle. As summer 2025 approaches, we should ask ourselves whether London workplaces are sufficiently equipped for similarly extreme – even potentially worse – heatwaves as we saw in summer 2020.
The high temperatures of 2020 were not just a statistical anomaly; they represented a scenario that building designers, engineers, and urban planners had largely pencilled in as unlikely until at least the mid-21st century. The scorching summer highlighted a pressing issue: much of London’s office real estate was underprepared for sustained heat extremes, and had the workforce been physically present, the consequences for health, comfort and productivity would have been severe.
Buildings Designed for Yesterday’s Climate
For decades, London’s office buildings have been constructed with the assumption that the city’s temperate, maritime climate would remain relatively stable. Traditionally, summers were mild, with average highs in the low-to-mid 20°C. As such, many office buildings either lacked high-capacity cooling systems and were equipped with systems designed only for moderate heat loads.
The 2020 heatwave shattered those assumptions. Temperatures in London soared well above 35°C on multiple occasions and night-time temperatures remained unusually high, compounding the thermal strain on buildings. According to the UK Met Office, 2020 tied with 2014 as the third warmest year on record, with several parts of the country experiencing one of their hottest summers ever recorded at the time.
In commercial properties, internal heat gains from lighting, computers, servers, and human occupancy are typically significant contributors to overall temperatures. Cooling systems are sized based on expected peak loads, but these calculations rely heavily on climate norms. With the sudden spike in outdoor temperatures, paired with climate change projections increasingly proving conservative, these systems would have been operating far outside their optimal design parameters.
A Quiet Crisis Averted by Remote Work
Ironically, the lockdown itself prevented a heat-related disaster in many of these office environments. With millions working from home, internal heat loads plummeted. Vacant desks meant idle computers, switched-off monitors, and zero body heat – all significant factors in keeping building temperatures lower than they otherwise would have been.
Had the pandemic not forced remote work on such a scale, the picture could have been dramatically different: offices running at full capacity, combined with inadequate cooling systems and unexpected external temperatures, would have posed serious risks. Overheating workplaces can lead to a sharp decline in employee productivity, increased health concerns, and in extreme cases, even heatstroke. Additionally, the energy demand for air conditioning surged, placing significant strain on the grid and inflating operational costs for businesses. All of this led to spaces becoming hotter and hotter until they could not be occupied at all – this included older, poorly ventilated buildings but also modern high glass proportion buildings.
Without the relief provided by remote work, some older or poorly ventilated buildings in London might have been forced to close temporarily due to safety regulations, compounding the economic stress already inflicted by the pandemic.
A Warning Sign for the Built Environment
The 2020 lockdown heatwave should have served as a stark wake-up call for London’s property owners, developers, and facilities managers. It exposed a critical vulnerability in the city’s commercial infrastructure: climate resilience had not been sufficiently prioritised in building design.
Of note, July 2022 also saw record-breaking temperatures in the UK: the first time that 40°C was recorded and a Met Office Red Extreme Heat Warning was issued. In the three days prior to the day of record-breaking temperature (19th July 2022), temperatures rose above 30°C across the country, which contributed to the overall challenge of dealing with the hazard. This was another stress test which placed immense strain on cooling systems. Since 2022, London has experienced heatwaves, but none as extreme as 2022, with cooler and wetter than average July and August months in 2023 and 2024. Attention should be given to the effects of heatwaves in 2020 and 2022 on cooling systems as we move into the summer of 2025.
Many of the modern office buildings constructed between the 1980s and early 2000s favoured sealed façades, heavy reliance on mechanical ventilation, and expansive glazing. These are aesthetic choices that, while visually impressive, increase thermal risk especially in respect to solar gain. Without sufficient internal and external shading, passive ventilation, or adaptive cooling strategies, these buildings become heat traps during extreme weather.
In spite of improved developments over the years, energy efficiency regulations have not anticipated the speed or intensity of climate shifts that are now materialising. Building performance models based on historical climate data are rapidly becoming obsolete, necessitating urgent updates to ensure future proofing against higher temperatures.
Whilst this piece focuses on commercial office spaces in London, residential properties have also been significantly impacted by heat-related hazards in recent years and are projected to continue to be. Prior to the relatively recent implementation of the Overheating Mitigation UK Building Regulation, Part O (effective from 15th June 2023), the Standard Assessment Procedure (SAP) was often used relating to solar gain and excess heat removal (overheating assessment), despite its focus on energy efficiency as opposed to thermal comfort. This means that a very significant proportion of residential properties – those which are not new or were converted since 15th June 2023 – did not have to comply with Part O upon their completion and therefore their thermal comfort is likely to be insufficient during extreme heatwaves.
Toward a Climate-Resilient Future
The 2020 heatwave highlighted the need for building designs that go beyond current energy efficiency towards true resilience, but adaptive features like passive cooling, smart ventilation, dynamic façades, and green roofs are not yet being implemented at sufficient speed due to the lack of tangible effects felt during the 2020 lockdown. These need to be seen as essential tools for survival in an increasingly unpredictable climate, rather than just best practice green initiatives.
Whilst the above resilient features are important for long-term adaptation, short-term solutions are also crucial. One of the most immediate fixes is to increase the capacity of existing cooling systems, enabling buildings to better cope with sudden spikes in temperature during extreme heat events. At the same time, it is essential to ensure that the electricity grid can reliably support this increased demand. With heatwave events now inevitable, these immediate measures are vital for safeguarding occupant comfort and maintaining operational continuity.
Additionally, the lockdown experience demonstrated the flexibility and viability of hybrid and remote work arrangements. With many companies now adopting long-term flexible work policies, the reduced occupancy of office spaces could help mitigate some thermal risks. However, this should not lead to complacency; resilient design must account for both occupied and unoccupied scenarios, especially as extreme heat events are predicted to become more frequent.
The Temporary Avoidance of Working from Home
Whilst working from home was mandated during the 2020 lockdown heatwave, many people now have the option of working from home. Aggregated across the year, this has led to a reduced need for office space for many companies in major cities such as London.
However, where housing stock cannot cope with high temperatures, for example where there are no air conditioning units, occupancy rates in offices may be seen to increase as people seek cooler climates to work in. This temporary trend reversal increases the demand and therefore pressure on cooling systems due to the body heat and technology sources previously mentioned.
Conclusion: A Lesson Hidden in Silence
The quiet, empty offices of London during the summer of 2020 narrowly avoided a heat-related crisis. As we move into the warmer months of 2025, it is very likely that climate extremes will be seen, and buildings will be stress tested once again on their resilience to heat-related hazards.
Since buildings were empty and systems off during the 2020 lockdown heatwave, we have not learnt the lessons we should have and therefore remain significantly vulnerable to such climate phenomena. Future buildings must be ready not just for the London of the past, but for the London of the future – a city where extreme heat is not the exception, but increasingly the norm.
At Longevity Partners, we have conducted multiple asset-level climate-related risk assessments in London and across the world, supporting clients in measuring their assets’ and operations’ vulnerability to material hazards, increasing assets’ adaptive capacity through innovative implementations strategies. To draw on this expertise, please reach out to Cameron McLaren and the Climate Resilience team at cm@longevity.co.uk.