Heat, Health & Housing: A Special Report
We often hear – and with very good reason – about cold, damp and mould issues in homes. But we rarely hear anything about the issues surrounding excessive weather-related heat. So in this report we will take a look at the problem, as well as the implications from a housing enforcement point of view.
Excess heat – an increasing problem?
The last figures from the World Meteorological Office (WMO) forecast that the annually averaged global mean near-surface temperature for each year between 2025 and 2029 is predicted to be between 1.2°C and 1.9°C higher than that over the years 1850-1900. They say that there is an 80% chance that at least one year between 2025 and 2029 will be warmer than the warmest ever year on record (2024).1
In summer 2022 the highest recorded temperature in England exceeded 40°C for the first time ever (40.3°).2
While climate change and global warming are frequently held up as causes there are a number of other factors at play when it comes to excess heat in the home. Legislative changes – such as the Future Homes Standard, rising EPC standards for rented homes and Awaab’s Law – have potential to make our homes warmer. And not always in a positive way, especially in times of hot weather. Rising energy costs in recent years have likely encouraged homeowners and tenants to prioritise insulation at the expense of ventilation.
The impact of excess heat in homes
In a country known for its frequently cold and damp weather it may seem odd that anyone would complain that their home is too hot. But, surprisingly, this is not an uncommon issue.
A University of East London study published in the Energy Research & Social Science journal found that the rate of overheating in UK homes increased from 11% of homes in the summer of 2011 to 80% in the summer of 2022.3
A study for the (recently closed) campaigning group Warm This Winter claimed that 4.5m people or 8% of the population have been so hot in their home that it has made them unwell in the last 12 months.4
It is not too difficult to find social media posts where tenants are having serious issues with excess heat. This is just one example our research found:
‘I’ve been living in my current flat for roughly a year now. It’s a 2015 conversion block of flats above a pub. The issue is whenever the weather starts to get warm or it's sunny at all the flat begins to heat up really fast. It’s currently 20°c outside but it’s 27°c in my flat and that's with all the blinds closed, extractors on and the windows closed when it begins to get hot outside. I’m disabled and do not have the funds to move out, plus I have a fixed tenancy with 6 months remaining so moving isn’t an option.
‘Do my landlords have to do anything about it or is it a situation I just have to deal with? With the heatwave last year it was getting to roughly 40°c and was unbearable.’
While much is heard, again with good reason, about the health risks of cold, damp or mouldy homes much less is heard about health risks in excessively hot properties. However excess heat in homes is known to cause heat exhaustion and heat stress, which can be fatal in extreme cases. It is said to exacerbate underlying issues such as cardiovascular disease, diabetes and asthma. It is linked with mental health issues and is also believed to increase the risk of accidents.
Properties that are at most risk
A report by the Climate Change Committee, prepared by Arup5, suggests which areas and types of property are most at risk of overheating.
The report says that London and the south pose a high risk, the Midlands and Wales have moderate risk, while northern England, Northern Ireland and Scotland face a limited risk – at least at current temperature levels.
The report says that smaller houses and flats are generally at more risk of overheating than larger homes. It adds that smaller bedrooms and loft rooms are more prone to overheating than other rooms, particularly where loft insulation is not present.
Specifically on insulation the report suggests that, while roof insulation produced a reduction in overheating risk in most cases, wall insulation presented a very different scenario. It said it could actually make a property hotter unless the room had adequate ventilation. The reports says: ‘This shows that measures undertaken to improve homes’ energy efficiency can produce undesirable effects on overheating performance.’
The Housing Health and Safety Rating System (HHSRS) suggests that flats and bedsits have a greater tendency to be affected by excess heat. It explains that this is because these are more likely to be badly insulated or under an uninsulated roof, have only a south facing aspect, or have heating systems that are not under the control of the occupier.
What the law says on excess heat
It is perhaps not surprising that housing law is much less vocal on the issue of excessive heat than it is on cold, damp and mould.
The Decent Homes Standard, currently for social housing but proposed for the PRS too, says that homes must provide ‘a reasonable degree of thermal comfort’. But this is clearly skewed towards ‘efficient heating systems and proper insulation’ (which paradoxically could make homes hotter).
The Housing Health and Safety Rating System (HHSRS) offers a little more guidance. Category 3 covers excess heat. It states that ‘This category includes threats from excessively high indoor air temperatures.
The guidance on assessing when excess heat could be a HHSRS hazard is somewhat vague.
The HHSRS suggests that the causes of excess heat are likely to be ventilation conditions. It says that the thermal capacity of the dwelling is relevant – smaller dwellings are more prone than larger. It also notes that causes could include properties with large areas of south facing glazing or faulty or sub-standard heating controls.
The HHSRS suggests a hazard assessment for excess heat should take account of provision for natural ventilation, especially at night, and the provision and condition of any mechanical ventilation or air conditioning. It also refers to the level and position of insulation, extent and direction of glazing and the state of repair of the heating system.
It suggests that 25°C could be the trigger point for what could be considered excess heat by saying ‘mortality increases in temperatures over 25°C.’
The age of occupants should also be taken into account. In this regard those over 65 are considered more at risk of health issues as a result of excess heat. (Interestingly, perhaps, the HHSRS does not take account of the fact different individuals have a different tolerance to heat.)
Part O of the Building Regulations came into effect in 2022 and affects residential buildings built after this date. It says that residential buildings should make reasonable provision to limit unwanted solar gains in summer and provide an adequate means to remove heat from the indoor environment.
The assessment procedure for Energy Performance Certificates (EPCs) is not orientated towards assessing thermal comfort in warm weather conditions. Part L of the Building Regulations (on conservation of fuel and power) are at odds with Part O to some extent.
Complaints and enforcement – a case history
Tenants who have issues with excess heat in their homes may, of course, take up the issue with their landlord. They can also pursue a complaint to their local authority in the usual way.
However it is very difficult to find any evidence of numbers of such complaints, or what the outcome was – if indeed such data exists at all. Indeed, the latest release of data from the English Housing Survey (EHS) on energy efficiency focusses firmly on damp and cold homes.
An interesting case in the First-tier Tribunal (Property Chamber) in 2024 – between Virginia House Ltd. and Worcester City Council6 – illustrates the difficulty of deciding if excess heat is an enforcement issue, what kind of enforcement might be appropriate and what kind of evidence is needed to support it.
In June 2023 the occupants of two flats in a block in Worcester complained to the local authority about excess heat in their homes. A subsequent inspection judged that a category 1 HHSRS Hazard of Excessive Heat was present. The local authority then issued Improvement Notices which required the installation of additional opening windows and/or air conditioning within a short timeframe. (It later transpired that the inspecting officers did not consider the situation appropriate for the issue of a Hazard Awareness Notice.)
The landlord responded to the local authority and cast doubts on the veracity of the inspection. They claimed that the weather was to blame, being excessively hot on the day of the inspection, and that to only consider the temperature on one day was not reasonable. The alleged that [ventilation] aids were deliberately turned off to inflate temperatures at the time of the inspection. (The landlord later argued that the property’s ventilation aids were adequate if used as intended.)
The landlord then appealed the Improvement Notices to the First-tier Tribunal.
The Tribunal visited the property alongside the parties themselves. They examined the physical layout of the property, including the position of windows and the provision of ventilation. They examined the methods by which heat levels had been recorded, including the use of an uncalibrated thermometer. They also looked at what had been done to attempt to remedy the issue, and at the experiences of other residents in the block.
In reaching its decision, the Tribunal also examined the procedure the local authority used to issue an Improvement Notice. In conclusion it found that the inspecting officers did not collect appropriate evidence, the policies and calculations were not appropriately applied, and the justification of the decision was not correctly recorded. It found that the time in which the landlord was required to carry out works was also ‘wholly unreasonable’.
The Tribunal ruled that the Improvement Notices should be quashed.
Conclusions: What should landlords do about excess heat?
Although excess heat is perhaps not the most pressing issue facing landlords at the moment it is certainly not something that should be ignored. So let us summarise by thinking about how landlords might address this issue.
Firstly, it might make sense to consider the issue when purchasing a property in the first place. Be aware that some types of property are more prone to the issue than others. A viewing on a cold, damp winter’s day may mask a serious underlying problem. An EPC report banding does not tell all of the story (or even any of the story) when it comes to excess heat.
When renovating a property that may be prone to excess heat, landlords might look at measures that could be installed – such as more opening windows, additional ventilation or blinds – to moderate the temperature in hot weather. Done at this stage the work is likely to be much more cost effective than a retrofit.
Given the health risks, landlords should certainly take any tenant complaints about excess heat seriously. In a country where warm weather is usually to be welcomed it seems sensible to assume that tenants will not complain about excess heat until it becomes a serious issue.
Should a complaint about excess heat be escalated to a local authority landlords might bear in mind that they are, to some extent, moving into a grey area. There is so little data and past experience to draw upon. Local authorities and the property tribunals do not have a great deal of experience in dealing with excess heat. Potentially anything could happen.
Sources:
1. WMO Global Annual to Decadal Climate Update (2025-2029)
2. Record breaking 2022 indicative of future UK climate – Met Office
3. A Nation Unprepared: Extreme heat and the need for adaptation in the United Kingdom – UEL
4. New research shows nearly one in 10 made ill by 'Hot House Syndrome' – Warm This Winter
5. Addressing Overheating Risk in Existing UK Homes – Climate Change Committee
6. Virginia House Ltd. and Worcester City Council – First-tier Tribunal
