Heat Ready London: A Wake-Up Call for a Warming Capital

As the UK experiences more frequent and intense periods of hot weather, overheating is becoming an increasingly important issue for homes, public services and infrastructure. Heat Ready London, the capital’s first dedicated heat resilience strategy, highlights the scale of the challenge and the action needed to protect people, buildings and essential services.

When Homes Become Too Hot

For many Londoners, particularly those living in modern apartment blocks with extensive glazing and limited opportunities for cross-ventilation, the recent heatwave pushed indoor temperatures to uncomfortable and potentially unhealthy levels.

Reports from residents across newer developments have highlighted growing concerns about how some homes are unable to cope with prolonged periods of hot weather. While energy efficiency has rightly remained a priority for the construction industry, overheating is increasingly challenging assumptions about how future-ready modern homes really are.

A notable example can be found in London’s Olympic Park. Reporting on a London Legacy Development Corporation survey found that only 39% of residents in Chobham Manor considered their homes comfortable during summer. Indoor temperatures were reported to regularly exceed 26°C, with many bedrooms becoming excessively hot.

The Strain on Services and Infrastructure

The consequences of overheating extend well beyond domestic comfort. During the heatwave, the London Ambulance Service recorded its busiest day in history, receiving 8,869 emergency calls in just 24 hours. Demand surpassed both the May heatwave and the peak pressures experienced during the Covid-19 pandemic.

Transport and education were also affected. Around 2,600 rail services were delayed or cancelled, Euston Station advised passengers not to travel unless necessary, travellers reported uncomfortable conditions on trains, and more than 1,000 schools and nurseries closed as temperatures climbed.

These impacts demonstrate that overheating is a wider resilience issue, affecting healthcare, education, transport and economic productivity.

The Economic Cost of Overheating

The economic implications of overheating are equally significant.

London generates 22.3% of the UK’s GDP, so disruption in the capital can have wider consequences for the national economy.

Heat is already affecting productivity and economic output. The Greater London Authority estimates that productivity losses linked to high temperatures were costing around £577 million each year in the early 2020s [5].

Poor sleep, reduced concentration and uncomfortable indoor environments can directly affect people’s ability to work effectively, particularly during prolonged periods of hot weather.

Heat Ready London

In response to these growing risks, the Greater London Authority has published Heat Ready London. The report sets out the scale of the challenge and the action needed to improve resilience across homes, public services and infrastructure.

The strategy focuses on five key objectives: protecting Londoners from the health impacts of high temperatures, reducing inequalities by prioritising those most at risk, adapting buildings and public spaces to provide shade and cooling, maintaining essential services, and supporting productivity and economic resilience.

London Was Ahead of Part O

London is not starting from scratch when it comes to overheating policy. The capital has considered heat resilience through planning policy for many years, well before the introduction of Part O of the Building Regulations in 2021.

Since 2008, developments seeking planning approval through the GLA have been required to consider overheating risk and follow the Cooling Hierarchy, which prioritises passive design measures, such as shading and natural ventilation, before mechanical cooling is considered.

From 2017, TM59 became the standard assessment method for residential overheating in London, helping to provide a more consistent approach to evaluating risk in new homes.

Part O later introduced a similar requirement into national Building Regulations, bringing overheating into the wider regulatory framework across England. In this respect, many of the principles now reflected nationally were already being applied in London through planning policy.

Awaab’s Law and Overheating

Heat Ready London also highlights that Awaab’s Law, introduced in 2025 to address damp and mould in social housing, is expected to be extended to cover additional housing hazards, including excess heat and overheating.

This represents an important shift in how housing quality is assessed and is likely to place greater responsibility on landlords and housing providers to identify and address overheating risks alongside other housing concerns.

Looking Back to Move Forward

One of the key messages from Heat Ready London is that many effective solutions already exist.

The strategy places strong emphasis on passive cooling measures, including external shading, natural ventilation, shutters, trees and green infrastructure. These measures are prioritised because they can help reduce overheating without increasing energy demand or placing additional strain on electricity networks during periods of extreme heat. Air conditioning will still be necessary in some settings, particularly in healthcare, care environments and buildings supporting vulnerable people. However, passive cooling is clearly positioned as the preferred first line of defence.

In many cases, this represents a return to design principles that were common in UK buildings more than a century ago. Features such as awnings, shutters, deep window reveals and natural ventilation were historically used to help keep buildings cooler during warm weather. As building design increasingly focused on retaining heat during winter, these features became less common, but they are now becoming increasingly relevant again.

The Challenge Ahead

Overheating is no longer a future risk. It is already affecting homes, public services, infrastructure and the wider economy.

As heatwaves become more frequent and intense, building design and retrofit will need to respond to the climate we are already experiencing. The challenge now is how quickly homes, buildings and communities can be adapted to improve comfort, protect health and strengthen resilience.

Further Information and Sources:

1. https://www.elmhurstenergy.co.uk/blog/2026/06/16/overheating-in-uk-homes-why-summer-comfort-can-no-longer-be-ignored/
2. https://www.elmhurstenergy.co.uk/blog/2026/04/09/government-announces-full-review-of-overheating-regulations-following-industry-feedback/
3. https://www.london.gov.uk/programmes-strategies/environment-and-climate-change/climate-change/climate-adaptation/heat-risk/heat-ready-london
4. https://www.london.gov.uk/heat-ready-london-londons-first-ever-heat-plan-sets-out-new-vision-protect-capital-extreme-heat
5. https://www.london.gov.uk/sites/default/files/2024-07/The_London_Climate_Resillience_Review_July_2024_FA.pdf
6. https://www.elmhurstenergy.co.uk/blog/2026/07/10/cibse-publishes-updated-tm59-overheating-methodology/