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by Sean Hill on Dec 17, 2025
For years, the UK built homes to keep heat in. Now we are discovering the uncomfortable truth: many of them cannot keep heat out.
Overheating in UK homes is no longer a niche concern or a theoretical future risk. It is happening now – in Victorian terraces, 1930s semis, post-war housing and contemporary extensions alike. Each summer, more homeowners experience sleepless nights, stifling internal temperatures and the creeping sense that their house is working against them.
The instinctive response is often to reach for technology: cooling systems, smart controls, or mechanical fixes layered onto an already struggling building. But in practice, overheating is rarely a technology problem. It is a fabric problem.
Designed to block high summer sun while welcoming winter light, the green concrete canopy and timber brise-soleil play a key role in preventing overheating.
Overheating starts with the building, not the gadgets
A home that overheats in summer is usually telling us something fundamental about how it is designed. Too much unshaded glazing, poor control of solar gain, gaps in insulation continuity, or uncontrolled air leakage all play a role. Add rising external temperatures and dense urban conditions, and the problem accelerates quickly.
The irony is that the homes most at risk are often those that appear “high performance” on paper. Large areas of glass, minimal shading and open-plan layouts may look modern and bright, but without careful fabric-first thinking they can lock in heat just as effectively as they lose it in winter.
In London retrofits and extensions, we regularly see internal temperatures exceeding 28°C for extended periods during summer. In some cases, this happens for more than 10% of the year – far beyond accepted comfort thresholds. Yet in many of these homes, active cooling could have been avoided entirely through better early design decisions.
A layered approach to overheating control: deep green concrete overhangs, external shading and a fabric-first extension designed for year-round comfort.
Why overheating risk is rising in UK housing
Several forces are converging. UK summers are getting hotter and more prolonged, while night-time temperatures – particularly in cities – are no longer falling enough to allow buildings to cool naturally. Urban heat island effects mean central London can remain several degrees warmer than surrounding areas well into the night.
At the same time, domestic architecture has shifted towards larger glazing ratios, especially in rear extensions. Floor-to-ceiling glass facing south or west has become a default move, often introduced late in the design process with little consideration of shading or ventilation strategy.
The result is predictable. Homes absorb solar heat during the day and struggle to release it at night. Opening windows is not always viable due to noise, pollution or security concerns. The building becomes a thermal trap.
External spaces that work with the climate - shaded terraces, planting and breathable materials helping to cool the home naturally in summer.
Orientation and shading: simple moves with outsized impact
One of the most effective ways to reduce overheating is also one of the most overlooked: responding properly to orientation.
South-facing glazing is not inherently a problem, but it must be paired with external shading. High summer sun can be blocked very effectively using overhangs, fins, brise-soleil or deep reveals, while still allowing valuable winter sunlight to enter the home.
West-facing glazing is more challenging. Low-angle afternoon sun is harder to control and often coincides with peak internal heat gains from cooking, appliances and occupancy. Here, external blinds, shutters, pergolas or carefully designed planting can make a dramatic difference. Sometimes the most sustainable move is simply to reduce glazing slightly without compromising the sense of space or connection to the garden.
Even north-facing elevations deserve attention. Without good insulation and airtight detailing, they contribute to winter heat loss and summer gains alike. Fabric performance is a whole-building issue, not something that applies only to “sunny” façades.
Insulation and airtightness: part of the solution, not the problem
A common misconception is that insulation causes overheating. In reality, insulation only traps heat if solar gain and internal loads are left unchecked.
Well-insulated, airtight homes perform better in summer when combined with shading and ventilation. They slow heat transfer from outside, retain cooler night-time air and prevent hot air from leaking in during the day. In fabric-first retrofits aligned with AECB or EnerPHit principles, we consistently see lower peak temperatures and more stable internal conditions.
This is where mechanical ventilation with heat recovery (MVHR) also plays a quiet but important role. MVHR does not cool a building, but it allows controlled night-time ventilation without relying on open windows. In noisy or polluted urban areas, this can be the difference between a home that sheds heat overnight and one that does not.
Ventilation as a design strategy, not an afterthought
Natural ventilation works best when it is designed into the building from the start. Cross-ventilation, stack ventilation and secure night-time purge routes all help remove heat without mechanical cooling.
Stairwells, rooflights and high-level openings are particularly powerful. As warm air rises and escapes at high level, cooler air is drawn in below. This simple physical principle often delivers more comfort per pound than any active system.
Yet ventilation is still too often treated as something occupants will “figure out” later. In reality, without deliberate planning, many homes simply cannot ventilate effectively during heatwaves.
Why fabric-first standards matter
Frameworks such as the AECB Standard provide a practical, UK-specific route to tackling overheating. By setting clear expectations around glazing ratios, shading, airtightness, insulation and summer comfort metrics, they help teams design homes that perform well without defaulting to cooling systems.
Passivhaus and EnerPHit go further, but the principle remains the same: control heat at source, then manage ventilation intelligently. Most homes can meet acceptable summer comfort levels without active cooling if these fundamentals are addressed early enough.
This approach also aligns with broader goals around energy efficiency, retrofit policy and long-term resilience. A home that avoids overheating today is far less likely to require expensive and carbon-intensive interventions tomorrow.
Designing for hotter summers ahead
The UK climate is changing faster than our housing stock. Designing for occasional hot days is no longer enough; homes must remain comfortable during sustained periods of high external temperatures.
Mechanical cooling will become more common, but it should be a last resort rather than a design starting point. Fabric-first design – prioritising shading, airtightness, insulation continuity and passive ventilation – remains the most reliable and cost-effective way to tackle overheating in UK homes.
The message is simple. If we want homes that are comfortable, healthy and resilient in a warming climate, we must start with the building itself. Get the fabric right, and the need for gadgets often disappears.
Building for a warmer future
At RISE, we believe tackling overheating in UK homes isn’t about adding more technology. It’s about designing buildings that work with the climate, not against it. Homes that stay comfortable through intelligent fabric-first thinking. That respond to sun, shade and air with quiet confidence. That are resilient enough for the decades ahead, yet simple enough to endure.
Designing for summer comfort is no longer optional. It is a responsibility – to occupants, to cities, and to a changing climate.
If you’re planning a retrofit, extension or new home and want to future-proof it against overheating while reducing energy use year-round, we’d love to help you get the fundamentals right.
Thinking about a fabric-first approach?
Let’s talk about how your home can stay cool naturally – and perform beautifully in every season.
→ Email us at architects@risedesignstudio.co.uk
→ Or call the studio on 020 3947 5886
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