To ensure better and more inclusive health outcomes, the TCPA has identified 12 Healthy Homes Principles that all new housing developments must provide. Each month, this blog series explores one of the Principles.
Healthy Homes Principle: Thermal comfort
The state of the UK’s housing stock is not just a matter of comfort but of life and death (Shahzad et al., 2025). Climate change, alongside with poorly insulated and inefficient homes, are leaving millions of people vulnerable to the increasing dangers of extreme temperatures.
In winter, excessive cold causes severe health problems and burdens residents and the NHS with preventable costs (BRE, 2023). Meanwhile, overheating in summer, exacerbated by climate change, is becoming an increasing threat, particularly for older people and those in urban areas (Basaly et al., 2024; UK Health Security Agency, 2024). Addressing thermal comfort issues thus requires a comprehensive approach that includes improving insulation, ensuring adequate heating, cooling and ventilation, and strengthening of housing regulations.
The dangers of cold homes
Cold homes are a major public health crisis in the UK, with millions of households unable to afford adequate heating. According to research, 9.6 million UK households are living in poorly insulated homes and struggling with energy costs (Friends of the Earth, 2024).
This has dire consequences for health, particularly for older people, children, and those with pre-existing conditions. Studies show that living in a cold home doubles the risk of adults developing new mental health conditions (Institute of Health Inequality, 2024). It also increases blood pressure, which can lead to heart attacks and strokes. Cold air restricts the airways, suppresses immune responses, and exacerbates damp and mould, leading to respiratory illnesses such as asthma and chronic obstructive pulmonary diseases. Conditions such as arthritis and sickle cell anaemia worsen in cold environments, while reduced dexterity increases the risk of falls, particularly for elderly residents (Institute of Health Inequality, 2024).
Children’s lung function and cognitive development can also be negatively impacted, with school attendance suffering as a result. Many families are forced to make difficult financial decisions between heating their homes, rental costs and other essentials, leading to increased malnutrition and stress-related health issues (Institute of Health Inequality, 2024).
The economic impact of cold homes is staggering. The NHS spends over £540 million a year treating people affected by the worst housing conditions, while the overall cost to the economy, including lost productivity and higher energy bills, runs into the tens of billions (BRE, 2025).
The NHS is spending over half a billion pounds a year treating cold-related ill-health caused by EPC F and G banded homes. (Building Research Establishment)
A national insulation programme, requiring an investment of £6 billion annually, could generate long-term savings that far outweigh the initial outlay (Friends of the Earth, 2024). And the Building Research Establishment (BRE) has called for the Warm Homes Plan to urgently prioritise the one in ten cold homes that have an Energy Performance rating of E or less (BRE, 2025). Addressing this issue would not only improve public health but also reduce fuel poverty, lessen the strain on public services and help to lower carbon emissions.
The growing threat of overheating
While the UK is traditionally associated with cold damp weather, the risk of overheating is an increasing concern. Climate change is driving more frequent and intense heatwaves, and millions of homes are ill equipped to manage high indoor temperatures.
Poorly designed, insulated and ventilated properties trap heat, making them dangerous during the summer months. More than half of UK homes, 15.7 million, fail to meet the bedroom overheating criteria, and an estimated 791 deaths occur annually due to excessive heat (TCPA, 2024). Increased temperatures can lead to and exacerbate cardiovascular, pulmonary, and respiratory conditions. Sleep disruption caused by excessive heat affects both mental and physical health, reducing productivity and worsening existing health conditions (Arup, 2022).
Older adults are particularly at risk, with mortality rates significantly higher among those aged 85 and over. A particularly dire example of heat mortality is highlighted by the four heat episodes of summer 2024, with 1,311 heat-associated deaths (UK Health Security Agency, 2024).
Source: UK Healthy Security Agency, 2024
Permitted development rights housing and the regulatory gap
Despite the clear risks, current building regulations do not adequately address overheating in homes produced through ‘permitted development’ (PD) conversion of former office blocks and other commercial buildings. While new homes must comply with Approved Document O of the Building Regulations, which sets overheating standards (Arup, 2022), these regulations do not apply to PD flats. This loophole leaves many residents vulnerable to extreme heat (TCPA, 2024), particularly in urban areas where temperatures are naturally higher due to the urban heat island effect.
Poorly insulated PD flats at Delta House, Croydon (credit: Rob Clayton)
The lack of thermal comfort in many PD conversions exacerbates both winter heating costs and summer overheating risks, aggravating an ongoing cycle of poor health and financial hardship (TCPA, 2024).
Additionally, the Decent Homes Standard, which requires social housing to provide a ‘reasonable degree of thermal comfort,’ only applies once buildings are in use. The standard is not a mandatory requirement for PD housing, or indeed private rented or owner-occupied homes. Too many people living in these properties are living in conditions that fail to provide adequate heating in winter or protection from overheating in summer (TCPA, 2024).
If the government is serious about tackling fuel poverty, improving health outcomes, and reducing carbon emissions, it must close legislative loopholes and ensure all homes, including those developed through PD rights, meet proper thermal comfort standards. This includes clear requirements in the Future Homes and Buildings Standard on ‘Overheating’ and ‘Excess cold’ for all housing tenures, and housing produced through ‘Material Change of Use’ and PD conversion.
Good practice: the Passivhaus standard in action
A compelling example of how housing can be built to mitigate both cold and overheating risks is the UK’s largest Passivhaus council housing scheme, of 496 homes – including 273 affordable council homes, at Agar Grove in Camden.
The development, designed to the Passivhaus standard, ensures homes are highly energy-efficient, with superior insulation and airtight construction (PassivHaus Trust – Phase 1 review) . This approach dramatically reduces heat loss in winter while also preventing overheating in summer. By using mechanical ventilation with heat recovery, these homes maintain a comfortable indoor temperature year-round, significantly cutting energy bills and improving residents’ health (Passive House +, 2020). Projects like this demonstrate that with the right design principles, it is possible to create homes that are both sustainable and protective of occupants’ wellbeing.
This flat is 100 times better than where we used to live. There is a huge difference in heating and hot water costs – much less than where we lived before. Agar Grove resident
The crisis of cold and overheated homes is not just a housing issue; it is a public health emergency. Without urgent action, millions will continue to suffer, and the NHS will bear the financial burden. Investing in better housing today will save lives, reduce healthcare costs, and build a more resilient future for everyone in the UK.
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Building homes that provide thermal comfort all-year-round, is a central Healthy Homes Principle in the Campaign for Healthy Homes. To promote thriving healthy and inclusive communities, a fundamentally different approach to delivering new homes is required – one that puts the quality and affordability of new homes and communities as highly as the quantity that are delivered.
Clémence Dye and Rosalie Callway
