Climate Change and Overheating

Our sustainability, flood risk and ESG experts discuss the impacts of climate change and overheating on businesses and the key considerations that need to be addressed to become future-ready.


The impacts of climate change will be felt all across society and industry. This paper will provide further insight into the risk arising from overheating and, importantly, how this will be felt by businesses.

While not unsurmountable, measures to protect and mitigate against these effects can require significant time to plan and implement.

It’s critical for businesses to become future-ready; to identify how they will respond to key issues and prepare clear actionable plans to mitigate the risks and benefit from the opportunities.

Focusing on the considerations for property owners, developers and investors, we discuss the key areas of vulnerability and provide guidance on where to begin.


Overheating in buildings

One of the associated challenges of rising temperatures is overheating in buildings. There is growing evidence of an increased incidence of overheating in buildings without air-conditioning during warm weather, especially homes in temperate climates where the retention of winter heat has been the principal focus of thermal design.

The overheating issue is shaped by considering:

  • Why is overheating a problem and why now?
  • How do people respond to heat?
  • Can we predict overheating?
  • How can overheating be addressed?


Why is overheating a problem, and why now?

Researchers at the University of Bremen in Germany have recently completed one of the most comprehensive investigations of the Earth's climate history to date and their findings are not encouraging. They found that without immediate and stringent action, our planet is on track for one of the strongest and fastest climate change events ever experienced; eventually warming to levels not reached in at least 34 million years.

The report identifies that Earth has passed through four distinct climate phases: Warmhouse, Hothouse, Coolhouse and Icehouse states. The transition between states has generally been the result of a change in greenhouse gas levels (often triggered by volcanic eruptions and other natural disasters) as well as shifts in the Earth’s orbit, affecting the levels of solar energy reaching the planet.

Source: Statista

At its hottest, more than 50 million years ago, temperatures on Earth were over 10°C hotter than they are today. But it took the planet thousands, or even millions, of years to reach these temperatures - long before humans existed.

That’s in blatant contrast to the climate change that human activity is causing today. The good news is this isn’t an inevitable future.

Organisations continue to position themselves as responsible and sustainable whilst pressures from consumers, infrastructure, climatic impacts and the government drives forward the pace of change. It’s clear that those who are best prepared will be the ones that succeed in the coming years. Are you ready?



Defined as prolonged periods of excessive heat, heatwaves are a specific type of extreme temperature event with many adverse impacts on human health, agriculture, workplace productivity, wildfire frequency and intensity, and public infrastructure. These impacts will increase as global warming progresses, where more rapid heatwave trends will likely produce more severe and possibly irreversible impacts in some sectors.


Predictions and statistics from major organisations in the sector:

This paints a foreboding picture of our future; faced with the many challenges and adverse impacts of overheating. It prompts the question: do your business operations need to be climate temperature controlled, where any deviation could be business critical?

Source: UKCP18 National Climate Projections

UKCP18 National Climate Projections

How do people respond to heat?

Excess heat affects the health and wellbeing of occupants, especially if sleep is degraded. In extreme cases, the heat stress caused can lead to premature mortality, particularly amongst more vulnerable members of society. This problem was highlighted by the devastating 2003 pan-European heatwave which caused an estimated 70,000 premature deaths. In territories where air-conditioning is already used, or even essential to maintain comfort, there is an interest in the indoor temperatures that might occur should the mechanical cooling equipment or the electricity supply fail. The concern here is survivability in relatively rare and unpredictable circumstances.

There are currently around 2,000 heat-related deaths in the UK each year.  Much of this increased risk is thought to be caused by exposure to high indoor temperatures. 

Apart from the very real human cost of this, there is also an associated economic cost. The first UK Climate Change Risk Assessment (CCRA), published by the Department for Environment, Food and Rural Affairs (Defra) in 2012, estimated that the cost from heat-related mortality due to climate change would increase from a total annual figure of £10-50 million now to between £25-150 million per year by 2050 and £40-350 million by 2080. This is classed as a ‘high magnitude’ risk according to the Government’s own criteria. Overheating risks to health also emerged as one of the top six key risks where more action is required in the most recent CCRA evidence report for Government, published by the Adaptation Sub-Committee in 2016.

Increased mortality is only one component of the effects of overheating. Illness, poor thermal comfort and reduced productivity and wellbeing are all major economic and social concerns, but there is almost no robust measurement of these impacts in the UK.

A good proportion of UK buildings are over 100 years old. These can be at higher risk because of overheating and climate change. These may require conversion or retrofitting to address the above risks.

Can we predict overheating?

There are many factors that will determine indoor summer temperatures in UK dwellings. These factors include:

  • The external climate
  • Location
  • Dwelling orientation
  • Room type
  • Time of day
  • Building fabric characteristics
  • Occupant behaviour
  • Air movement
  • Shading, reflection and protection

A number of studies by RPS have identified that an unintended consequence of high insulation and air tightness standards of newly built and retrofitted houses may be overheating. Communal areas, corridors and elderly homes are among the areas which are more at risk.



How can overheating be addressed?

It has been suggested that changing the positioning of insulation, i.e. external rather than internal, may minimise the risk of extreme temperatures during the summer. Our study shows that generally, thermal mass coupled with night cooling through ventilation has been identified as a relatively effective measure to combat domestic overheating. Thermal mass refers to how light or heavy the structure is and is defined as the ability of a material to absorb and store heat energy. Another key finding with significant implications for design and operation is that natural ventilation may become a ‘double-edged sword’ in the future, coupled with low G-value glazing which determines how well the glass transmits heat from the sun.

As ambient temperatures are projected to increase, daytime ventilation may not be beneficial for the mitigation of overheating as the incoming air will be at a high temperature. In addition, night purge ventilation will be effective only if the diurnal temperature variation is significant enough to flush away the heat stored in the building. However, this is also likely to change under current climate change projections. Night-Purge Ventilation (or "night flushing") keeps windows and other passive ventilation openings closed during the day, but open at night to flush warm air out of the building and cool thermal mass for the next day.


Wider environmental impacts

Though an obvious conclusion, the increased heat will lead to more droughts in the UK. However, what is perhaps not as obvious are the far-reaching consequences of these droughts. With the advent of longer and more frequent heatwaves, the summer periods become dryer - not only because less rain falls but because the rain that does fall tends to fall in shorter and more intense storms. Such rainstorms cause water to move quickly to streams with far less infiltrating into the ground. The result is that the groundwater tables around the country are not recharged, and this is happening at a time when the vegetation will draw more water from the groundwater to help them deal with the intensified hot weather.

The result of this is less water for vegetation. And this leads to a phenomenon called “stress” which eventually kills off grass, trees and bushes. Following a few summers of this type of weather, root systems are destroyed and bare earth is exposed. The intense rainfall washes away the exposed soil and less water is held back to infiltrate into the groundwater, leading to longer and more severe droughts. What makes these processes so dangerous is the fact they are happening year on year and so there is little chance for nature to recover.

Drought - cracked soil

The flipside of the coin is that the occurrence of shorter sharper rainstorms during heatwaves is exactly the type of storm that is the most dangerous for creating flash flood events. These events are created from the fact that hot air can hold more water vapour, but the more water held, the less of a change is needed to create a devastating rainfall. The process of water vapour coalescing into raindrops releases energy that manifests itself as wind. This wind moves more air and under some circumstance brings increased vapour-filled air into the location of the rainstorm, further fuelling it. These flash floods are far less predictable, in terms of location, than the river floods and can occur almost anywhere.

The reduction of the groundwater table during summer months means that the ground will store more water during the winter months, which is a slight positive as it takes away a minor amount of water in our rivers that otherwise might contribute to flood conditions. However, large changes in groundwater levels between summer and winter months will destabilise soils, especially in embankments and along slopes, leading to more frequent landslides.


Checklist: Water considerations you should be addressing

  • Are you aware of where water flows around you? Just because flooding has never happened before does not mean that you are not at risk
  • Are your assets in good working condition? With sudden flash flooding a reality almost everywhere, a poorly maintained drainage network can spell disaster
  • Are you vulnerable to water shortage? We take water for granted but what would happen to your business if there were restrictions placed on water consumption?


  • Is your supply chain reliant on water? You could find yourself subject to second tier impacts
  • Have you got responsibility for amenity areas with green infrastructure? If so, are you looking out for early signs of water stress? Early intervention could be necessary to maintain operation without major disruption
  • Are you looking to how you can reduce your water consumption/reliance? This would benefit society as a whole as well as protect you

The impact of climate change on businesses

Aside from the social impacts mentioned above, businesses are likely to see increased energy demand from air conditioning. There will be a need for enhanced building or plant specifications and operational capital expenditure to cope with climate variability and consequential increases in carbon emissions. Business assets will need to be future-ready.

In terms of day to day business, new strategies and performance improvements will need to consider how businesses will remain on-target with existing commitments made on climate action and resource efficiency. This is where it helps to have a good technical partner on-board to anticipate and navigate business operations through these changes.

What is clear, is that very few sectors will be unaffected moving forwards. From property estate managers, investors and asset owners through to insurers, the cost of maintenance and refurbishment is set to rise. The industrial sector will likely witness impacts as refrigerant demands change, affecting the chilled / frozen food sector and data-site operations against a rising growth of demand fuelled by e-commerce (more so during Covid-19 restrictions). The rising energy demand and refrigerant specifications will require careful consideration.

Outside of these areas, key commercial areas in the UK are reliant on raw materials and agricultural commodities. We acknowledge that in the above scenarios, increased water demand from crops due to overheating may be unsustainable in the medium-longer term, leading to water scarcity issues that have far wider reaching implications for business and society as a whole.

Covid-19 has focused the minds of business leaders and has exposed weaknesses in the way business activities, operations and supply chains are managed. Many are taking the time to act now and are preparing themselves for a more normal return to business that is better prepared to adapt to climate change impacts.

Checklist: Are you future ready?

  • Have you considered climate change risks and opportunities in your business?
  • What would be the impact if investors and lenders would no longer engage with or fund your business, owing to a lack of response on climate matters?
  • Do your operations need to be climate temperature controlled, where any deviation could be business critical?


  • Does your business rely on agricultural and labour-intensive supply chains that are time or availability dependent?
  • What would be the impact on your operations if the availability of water resources for production were to be cut?
  • What impact would there be on your future business if the availability of workers were to change through migration complications due to climate change or water shortages?

How we can help

At RPS we have an experienced energy and sustainability team, specialising in overheating and thermal comfort assessment for both residential and non-residential buildings. We use advanced 3D modelling and CIBSE TM 59 and TM 52 to model and assess potential overheating issues, followed by assessing the potential effectiveness of remedial measures.

We also have a strong multidisciplinary environment team who can provide all the relevant know-how needed to ensure that assets such as roads and buildings, agricultural land and landscaped gardens and all other built environment assets are designed in a manner that renders them heatwave resistant. The Sustainable Business and ESG team can help businesses assess the liabilities associated with heatwaves and plot the best course of action to minimise the future impact of what we all can see is coming.

Thanks to the RPS Energy & Sustainability, Hydrology and Sustainable Business & ESG teams for their contribution to this White Paper.


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