Beat the heat: the dangers of letting your buy-to-let overheat

Our weather patterns are changing. This year’s successive heatwaves have shifted the thermal comfort conversation.

Homes that are too cold and damp in the winter are no longer the sole talking point. Now we are seriously evaluating properties that are unbearably hot to live in during the summer.

What does this mean for landlords and tenants? The message is clear: the private rental sector needs to improve standards when it comes to living with extreme weather.

A mandatory matter when the mercury rises

Controlling excess heat isn’t something landlords can opt out of. Creating a humane level of thermal comfort is mandatory, as detailed in England’s Decent Homes Standard. While there is no set regulation on excess heat in Scotland, this can still legally constitute a health hazard if caused by structural defects or lack of ventilation.

An estimated 441,000 private rented homes in England failed thermal comfort standards in 2024. The figure was the result of analysis by Inventory Base, using the latest Decent Homes Standard (DHS) data published by the Government.

Worryingly, 2024 was hot but not a record breaker. Summer 2025 is currently the UK’s warmest summer on record but for how long? Long-held heat records have already been broken in 2026 and August isn’t even over. To put the new levels of heat into perspective, the Met Office has said this summer is the first ever where a temperature of 35°C was reached in May, June and July. 

Measuring thermal comfort 

Levels of thermal comfort in England and Wales are measured using the Housing Health and Safety Rating System (HHSRS). This was revised on 23rd June 2026, making the identification of hazards easier.

The risk classification system was changed, with the previous A-J rating bands replaced with a High, Medium and Low. Additionally, the four classes of harm have been renamed to Extreme, Severe, Serious and Moderate.

The number of hazard categories was also reduced, decreasing from 29 to 21. Each is deemed a threat to an occupant’s health, safety and wellbeing. Number 14 is excess heat - classified as physiological hazard and characterised by a lack of ventilation that can cause a property to become overheated, airless and stifling. 

How can a tenant complain?

If a tenant feels their home is unbearably hot to live in and their landlord has failed to take action, they can make a complaint to their local authority. It’s highly likely a local council officer will visit to carry out an inspection. They will use their findings to make an assessment using the HHSRS framework.

The assessment will concentrate on the risks posed to the most vulnerable person in the property. In the case of extreme heat, this would be the elderly, infants, young children and people with chronic pre-existing medical conditions.

A score is generated for each hazard being assessed. A thermal comfort issue can be classed as a Category 1 hazard - a high risk – or a Category 2 hazard, either moderate or low risk.

Forced to cool off

If thermal comfort has been identified as an issue, the local authority can take one of five steps, depending on the severity. These range from a Hazard Awareness Notice (guidance for landlords where the hazard is minor) to Emergency Remedial Action (a hazard so grave the council can immediately undertake work).

Landlords who ignore category 1 hazards can receive civil penalties of up to £7,000.

How hot is too hot at home?

The ideal indoor air temperature is 18°C, which is easily surpassed in the summer. As a guide, the World Health Organisation (WHO) advises that an internal temperature of 24°C or above is excessive. 

Why might a property get excessively hot?

Older property stock and homes not built to accommodate hot weather are common in the UK. These aspects can all contribute to a home overheating:

• poorly insulated structures

• windows that are painted shut or broken to the degree they can’t open

• windows that, if open, create a fall risk, let in unsafe levels of pollution or present a security risk

• rooms directly below uninsulated roofs

• lack of ventilation and cross ventilation

• high levels of solar heat gain through windows, skylights and large areas of glass 

• inadequate heating controls

• materials with low thermal mass that do not regulate temperature well

How to improve thermal comfort 

Taking action to increase thermal comfort is a wise investment, especially as The Climate Change Committee has claimed 92% of existing homes could be at risk of overheating by 2050. Action could include:

• fitting external shades, shutters or awnings, especially to south facing orientations

• installing air conditioning

• applying heat reducing window film

• ensuring all windows open, with appropriate safety latching

• eliminating fall risks so tenants feel confident to open windows and doors

• repainting exteriors in a lighter-coloured or solar reflective paint 

• improving insulation and cross-ventilation

• ensuring central heating can be turned off

If you would like help meeting landlord compliance requirements, get in touch. Our property management team can take over the running of your rental so it’s always safe and legally sound.