As UK summers become warmer, keeping our homes comfortable in hot weather is becoming just as important as keeping them warm in winter.
And this is no longer simply a theoretical concern. In 2025, the UK experienced its warmest summer on record, with a mean temperature of 16.1°C – 1.51°C above the long-term average. The five warmest UK summers on record have all occurred since 2003.
Overheating in homes is already widespread. The latest English Housing Survey found that around 3 million homes were reported as overheating in 2024, equivalent to 12% of occupied dwellings. That proportion has risen from 7% in 2019.
New build overheating is therefore becoming an increasingly important design consideration, with summer comfort now just as important as winter performance.
Large areas of glazing and highly insulated, airtight construction can create beautiful, energy-efficient homes, but without careful design they can also increase the risk of excessive summer temperatures.
The answer doesn’t necessarily have to be air conditioning. At our Mudeford Passive House in Christchurch, Dorset, we have used a fabric-first approach to create a low-energy home designed to remain comfortable throughout the year.
Start with orientation, not technology
One of the most effective ways to prevent a new home overheating is to consider the sun before the building is designed.
At Mudeford, we carefully considered the site’s orientation, sun path and prevailing conditions from the outset. South-facing glazing can provide useful solar gain during colder months, while carefully designed shading limits excessive solar gain when the summer sun is higher.
This approach reflects the Passivhaus Trust’s guidance on avoiding summer overheating, which emphasises that overheating should be considered from the very start of the design process, with building orientation, glazing and shading designed together.
Getting these fundamentals right early can significantly reduce the amount of energy needed to both heat and cool a home.
Design out overheating with solar shading
Well-positioned windows provide natural light, views and a strong connection with the garden, but large areas of unprotected glazing can also introduce significant amounts of solar heat.
External shading is one of the most effective ways of reducing solar gain, with fixed measures such as roof overhangs and brise soleil particularly robust because they do not rely on occupants remembering to use them.
The latest English Housing Survey data provides a useful reminder of the scale of the issue: 2.3 million homes that reported overheating in 2024 had little or no overshading of their windows.
At Mudeford, solar shading is therefore considered as part of the architecture itself rather than something added later to solve an overheating problem.
The principle is simple: welcome lower winter sunlight while limiting the stronger summer sun.
How do you stop a new build house overheating?
The most effective approach is to tackle overheating through the design itself:
- Consider orientation from the outset.
- Control the amount and position of glazing.
- Incorporate effective external solar shading.
- Design for cross-ventilation and night-time cooling.
- Create a highly insulated and airtight building envelope.
- Assess summer performance as carefully as winter performance.
These decisions are much easier – and considerably more cost-effective – to make during the early stages of designing a home than to correct once it has been built.
How insulation and thermal mass can help prevent overheating
A fabric-first approach isn’t only about keeping a home warm.
High levels of insulation help create a more stable internal environment, while appropriate thermal mass can help moderate changes in temperature. Airtight construction also gives much greater control over how air moves through the building.
Insulation, airtightness, glazing, shading, thermal mass and ventilation should therefore be considered as one integrated environmental strategy rather than as individual technologies.
Use natural ventilation and night cooling to remove excess heat
Preventing unwanted heat entering the house is only part of the solution. A home also needs an effective summer ventilation strategy to remove excess heat.
This matters because, when homes do overheat, opening windows is by far the most common response.
Carefully positioned openings can encourage cross-ventilation, while secure night-time ventilation through stack effect can allow cooler outside air to purge heat accumulated during the day.
This is another key principle highlighted by the Passivhaus Trust: once unwanted heat gains have been minimised, designers should maximise opportunities for passive cooling, particularly through window ventilation, cross-ventilation and cooler overnight air.
A Mechanical Ventilation with Heat Recovery (MVHR) system provides a continuous supply of filtered fresh air throughout the year, but summer comfort starts with reducing excessive heat gains and providing effective passive ventilation rather than relying on mechanical cooling.
Designing homes for hotter UK summers
Good Passivhaus design is about more than reducing winter heating bills. It means designing for comfortable living throughout the year.
For Passivhaus projects, summer comfort is an important part of performance assessment, with designers aiming to minimise the amount of time internal temperatures exceed comfortable levels.
That target becomes increasingly relevant as the UK climate changes. Summer 2025 was the warmest on record, and by mid-July 2026 the UK had already recorded more days above 30°C than during the whole of 1976. The Met Office also reported that 2026 had, by that point, become the first year on record to reach 35°C in May, June and July.
Mudeford Passive House demonstrates how orientation, solar shading, insulation, airtightness and ventilation can work together to create a low-energy home that responds naturally to its environment.
Design for comfort from the very beginning
At Footprint Architects, we believe the best time to address new build overheating is at the very beginning of the design process.
By working with the sun, climate and site rather than against them, we can create sustainable homes that are comfortable today and better prepared for the changing climate of the future.
Frequently Asked Questions
Can a new build home overheat in summer?
Yes. Highly insulated and airtight homes can still overheat if glazing, solar gain, shading and ventilation are not carefully considered. Good design should address summer comfort from the outset, not just winter energy efficiency.
Does insulation make a house hotter in summer?
Not necessarily. Insulation helps slow heat transfer in both directions and can help maintain more stable indoor temperatures. Overheating risk is more closely linked to factors such as excessive solar gain, large areas of unshaded glazing and inadequate ventilation.
How can you cool a new home without air conditioning?
Passive cooling measures can include careful orientation, external solar shading, cross-ventilation, night-time cooling and appropriate thermal mass. Used together, these strategies can significantly reduce reliance on mechanical cooling.
Can a Passivhaus stay cool in hot weather?
Yes, provided summer comfort is considered carefully during the design process. Passivhaus design looks at factors including glazing, shading, ventilation and overheating risk to help maintain comfortable internal temperatures throughout the year.
Why choose Footprint Architects?
At Footprint Architects, we believe great architecture should do more than look beautiful, it should improve the way people live. Our approach combines thoughtful Passivhaus architecture, sustainable design, and technical expertise to create homes that are comfortable, healthy, and built for the future.
Planning a new home and want to make sure summer comfort is considered from the outset? Get in touch with us to discuss how a fabric-first, climate-responsive approach can help create a comfortable and energy-efficient home throughout the year.
Case Study: Mudeford Passive House
Mudeford Passive House is a new-build sustainable home designed to Passivhaus standards within a sensitive historic coastal setting. The design uses a fabric-first approach, combining high levels of insulation, airtightness and carefully positioned glazing to reduce energy demand and improve year-round comfort.
The result is a low-energy home that balances environmental performance, comfortable family living and a strong connection to the garden. Explore the Mudeford Passive House project to see how these sustainable design principles were brought together.
