The government’s warm homes policy has a major contradiction

The Warm Homes Plan is fundamentally about enabling people to live affordably in their homes, using modern and renewable technologies to reduce energy consumption and carbon emissions at a time when fuel poverty is rising. That principle is sound.

Equally, well-ventilated homes are directly linked to good health and well-being. Overheating has a measurable impact on physical and mental health, including sleep quality, metabolic health and productivity.

An occupant-centred approach therefore has to underpin the Warm Homes Plan, balancing affordability with health outcomes. The policy’s recognition that passive or active cooling may be required to mitigate overheating is an important acknowledgement that energy efficiency alone is not enough – but it remains a complex challenge to address.

“Highly insulated, airtight homes – including those built to high specifications and Passivhaus principles – can be vulnerable to excessive internal temperatures if ventilation and heat removal are not carefully designed in”

The risk of overheating is surprisingly acute in well-performing homes. Highly insulated, airtight homes – including those built to high specifications and Passivhaus principles – can be vulnerable to excessive internal temperatures if ventilation and heat removal are not carefully designed in at the outset.

For residents in affordable housing – including older people and those requiring specialist care – getting this balance wrong has serious consequences. The response to the Warm Homes Plan therefore needs to be right first time, with health and well-being underpinned by the appropriate level of technical expertise and correct and ideally regulated execution.

Well-insulated buildings make absolute sense, but insulation, airtightness and ventilation must be addressed as part of a cohesive energy strategy.

Comfort cooling is a more practical solution for reducing temperature. Air conditioning also manages humidity but is energy-intensive, maintenance-heavy and costly to run, even when paired with solar. However, there is significant untapped potential in passive measures such as external shading, blinds and shutters – commonplace in warmer climates but still under-utilised in the UK.

Overheating cannot be considered in isolation. Whole-life carbon, operational emissions from heating systems, materials selection, and long-term maintenance and repairs all need to be addressed as part of the transition away from fossil fuels and towards more energy-efficient homes.

Ventilation may be key to passive cooling, but real-world constraints quickly emerge.

The external acoustic environment matters – homes adjacent to busy roads or railway lines may not be able to rely on opening windows for ventilation without compromising well-being. In dense urban areas, background noise can itself become a health issue.

Regulatory requirements will also shape the solution. The Building Safety Act requires consideration around fall protection, which may limit window openings through restrictors.

“The starting point is to treat each building as a whole, rather than a suite of measures to be installed”

Air pollution is another constraint, particularly in city centres. The layout of multi-occupancy housing can severely limit natural cooling strategies. Traditional apartment layouts – with homes on either side of a corridor – make cross-ventilation for cooling extremely difficult, regardless of insulation levels.

These inter-relating factors vary widely depending on location, building age and housing typology. Improving thermal performance through additional insulation also introduces the risk of interstitial condensation if ventilation levels are not properly understood. There is no silver bullet or single solution.

The starting point is to treat each building as a whole, rather than a suite of measures to be installed. No single element should be changed without first getting clarity on how it affects the whole property and its occupants. This requires time, analysis and robust thermal modelling, enabling housing providers to understand, at a systems level, what interventions will deliver the greatest benefit without creating new risks and health hazards such as condensation or overheating.

Technology is rapidly advancing. The first ventilation systems with integrated cooling are now available and can be combined with building fabric upgrades and low-energy renewable heating. Where roof orientation allows, solar energy can help offset the additional electrical demand of these cooling systems. But technology alone is not the answer.

Occupant-profiling is critical. Homes occupied by older or more vulnerable residents, who are likely to remain in the property during the day, need to perform very differently from those properties occupied mainly in the evenings. Overheating in daytime is harder to mitigate than night overheating, and these factors need to inform the performance strategies from the outset.

There are significant risks to undertaking blanket upgrades to heating, glazing and insulation without detailed analysis. Homes can take many hours to cool once overheated, and what appears to be a sensible energy upgrade in theory may be hugely detrimental to resident health and well-being, and may increase risk of non-compliance with Awaab’s Law.

There is a delicate balance between resident comfort, health, running costs and carbon emissions, and it cannot be achieved without detailed analysis, modelling and complex calculations.

New build affordable homes have more flexibility – window orientation, shading and layout can all be optimised. Retrofit is more challenging.

Orientation of roofs or windows cannot be changed; internal insulation reduces room sizes, and the existing interior is someone’s home. The solution will differ from building to building, even across similar typologies. The key is to design for residents – present and future – rather than relying on standardised assumptions.

The new legislation rightly raises expectations around building safety, health and affordability, but overheating must be treated as a core risk, not an afterthought. Without a holistic, evidence-led approach, these well-intentioned policies risk poor outcomes for the very people they are designed to help.

However, this is also a huge opportunity to increase the affordability, health and resilience of social housing in a changing climate.

Doug Johnson, founding director, Mesh