London Homes Are Overheating - But We Can Design Our Way Out of It

I sat down recently with BBC London's Alice Bhandhukravi to talk about a problem that's quietly shaping homes across the capital: overheating. Only a small part of that conversation made the broadcast, but we spent the best part of an hour on why so many London homes are now too hot in summer, and what architecture can do about it.

It's something we think about constantly at RISE, and not as a problem to solve with expensive kit. Most of the answer is in climate-responsive design: the decisions about orientation, shading and ventilation that make a house comfortable without leaning on mechanical cooling.

Sean Ronnie Hill of RISE Design Studio, interviewed by BBC London on how better design can reduce the risk of overheating in the capital's homes. RISE Design Studio.

Why so many London homes overheat

Much of London's housing was never built for the climate we now have. Victorian and Georgian houses were made to breathe: open fireplaces kept air moving, single glazing leaked heat, and high ceilings let warmth rise away from the rooms people used. They were inefficient in winter, but surprisingly tolerant of heat in summer.

Over the last twenty years, a lot of those houses have been sealed up in the name of energy efficiency. Draught-proofing, double glazing, insulated roofs and airtight construction have transformed their winter performance. But without matching attention to ventilation, shading and solar control, many of them now struggle in the warmer months.

Large glazed extensions facing west or south-west, unshaded rooflights, dark roof finishes and exposed thermal mass all push in the same direction. In a long heatwave, a house absorbs heat all day and releases it slowly into the evening, exactly when people are trying to sleep. The result is familiar across London now: bedrooms that stay too warm well into the night.

It isn't only the buildings, it's the city

The problem is also urban. London has a pronounced heat island effect, where dense expanses of asphalt, brick, concrete, paving and dark roofs soak up heat during the day and give it back slowly after dark. Areas with few trees and little open ground stay markedly warmer overnight than greener parts of the city.

Kilburn, where we've worked on several projects, is a good example. In a summer heatwave its night-time temperatures can sit well above those a short distance away in Regent's Park, where mature trees, planting, open ground and evaporation cool the local air. For anyone in a top-floor flat, a poorly ventilated terrace, or a heavily retrofitted house with no external shading, that's a real and growing discomfort, not a distant one.

What older buildings already knew

The irony is that the most effective cooling ideas aren't new. Around Barcelona, southern Spain and much of the Mediterranean, buildings evolved over centuries to handle heat without machinery. Deep balconies threw shade, external shutters stopped sunlight before it reached the glass, recessed openings cut solar gain, and tall rooms encouraged air to move. None of it was decorative. It was a response to the climate.

We draw on the same principles when we design and retrofit in London. The measures that tend to work are external shading that intercepts sun before it reaches the glass, such as a brise soleil, pergola, canopy or deep overhang; external blinds or shutters, which beat internal ones because they stop the heat outside the building; opening windows positioned to drive cross ventilation; rooflights placed to purge hot air by stack effect; restraint with unprotected south-facing glazing; and planting around the house to add shade and a little evaporative cooling. Passive design isn't primitive. Most of the time it's simply the smarter option.

Designing the comfort in before site starts

We model how a building will behave long before anything is built, using detailed environmental simulations and digital twins. That lets us test how sun, airflow, shading and thermal mass interact across the year: analysing peak summer solar gain, seeing how external shading changes internal temperatures, simulating airflow through stairwells and rooflights, finding the rooms most at risk of overheating, and comparing options before any expensive decisions are committed on site. The point is to design the comfort in from the start, rather than relying on mechanical systems to paper over an avoidable problem later.

Technology matters, but design comes first

Technology has a real role. Air-source heat pumps, MVHR, intelligent controls and high-performance glazing all help. But they work best alongside good passive design, not as a way to compensate for poor orientation or too much glass. Our order of priority is usually passive measures first, efficient systems second, and conventional air conditioning only where it's genuinely needed.

That order matters beyond any single house. Conventional air conditioning uses a lot of electricity and dumps waste heat into streets that are already too warm, so the more homes that install it, the hotter the city gets. Architecture should be reducing the need for cooling rather than treating it as the default.

Designing for a warmer climate

Overheating is becoming one of the defining design problems for cities. The homes that perform best over the next fifty years won't necessarily be the ones with the most technology. They'll be the ones that face the right way, shade themselves, ventilate naturally and respond to the climate around them. Comfort isn't a luxury bolted on at the end. It's one of the things good design is supposed to deliver in the first place.

If you're worried about overheating in your home, or planning a renovation or extension and want to get ahead of it, we'd be glad to talk it through.

→ Email us at architects@risedesignstudio.co.uk

→ Or call the studio on 020 3947 5886

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