Trading up: preparing old and new urban housing for higher temperatures

How can #London and other #cities ensure their aged #urban housing stock and new buildings will be ready for higher #temperatures? Innovations in Britain’s colonies at the end of empire provide lessons on delivering #sustainability amid climate change.

Homes in cities in northern countries such as the UK, France and Germany were often built over the last century or so to withstand generally cool and damp conditions. Many were built long before modern insulation was commonplace.

The brick or thick stone walls of houses and apartment buildings and the reinforced concrete and steel of tower blocks were designed to retain warmth during cold winters, not shed heat during scorching summers. Older wooden buildings with many windows  with low-quality, poor insulation also struggle in extreme heat. Top floor apartments or those with dark-coloured roofs can turn into literal ovens when temperatures soar. One answer is air conditioning but that can be very energy intensive.

And the outlook is getting more dire. The 2023 European heatwave caused the deadliest summer on record. Just under 63,000 people died in Europe from heat-related causes, according to a study in the scientific journal Nature Medicine — many of them isolated elderly people in urban areas.

Last year is not likely to be a one off. According to the UK’s Met Office the temperature of hot summer days, by the 2070s, show increases of 3.8 °C to 6.8 °C, under a so-called “high emissions scenario”, along with an increase in the frequency of hot spells. As the climate continues warming, fatal heatwaves could become a more regular occurrence.

This means that policymakers in cities, which are likely to have worse problems because of the urban heat island effect that keeps temperatures hotter, need to take decisive action now to retrofit existing housing and ensure new construction is designed for the new climate reality. There are some, relatively easy wins. Upgrading insulation and ventilation for temperature control, replacing old windows with double or triple-paned versions, adding wall and attic insulation, and installing shades or window tints can all make a big difference.

Not that that would be cheap and the bill would depend on how extensive the interventions were. Work by the Climate Change Commission and Arup looked at a number of packages. One scenario included installing blinds, roof insulation and low G-value window film — which blocks all solar energy — as well as active cooling for some modern flats in London to completely eliminate the overheating risk. They estimated the bill at around £250 billion, (including for the London flats) or five times the UK’s annual defence budget.

Given the low prospect of either major party including this in their 2024 general election manifesto, the next step is to look at what changes can be made to regulations for building new homes (remembering that a Labour government would build 1.5 million over the next five years).

Open facades and sun shades

An exhibition at the Victoria & Albert Museum in London that profiles two post-war British architects, Jane Drew and Maxwell Fry, shows that the past can offer useful lessons for the present (even if that history is itself severely tainted).

The focus is on the pair’s work to develop an architecture that would be suitable for the hot and humid conditions in parts of what was then the British Empire. They were among the British Modernist architects to take the view that new buildings made using concrete, glass and steel would create a better world.

Post-war Britain was not yet ready for that more severe style of building and the exhibition makes clear that Fry and Drew were able to find opportunities in West African countries then under colonial rule such as Nigeria, Gold Coast (now Ghana), Sierra Leone and Gambia

They used what was then the latest science around the environment and construction to create what is now known as Tropical Modernism aimed at providing passive cooling, maximising shade and allowing better ventilation.

Techniques included positioning buildings so that solid walls on the East and West blocked the strongest sun while the longer North and South aspects were more open. The exhibition shows how they used techniques such as brise soleils or semi-permeable screens that can divert direct sunlight while allowing a cool breeze to enter. Using long overhanging edges known as wide eaves can keep sunlight off the windows while using adjustable slats can take account of the movement of the sun to keep the heat out.

While modernism took off in the UK with the Southbank Centre and the Barbicani in London and many council offices and car parks around regional cities, Fry and Drew’s climate-resilience ideas did not form part of general building styles. For example, modern office buildings feature huge arrays of glass (with some unfortunate consequences).

As we move further towards a climate emergency perhaps the architectural ideas and practices of Tropical Modernism — shorn of their colonial-era origins — can inform domestic and business construction in an era of hotter and wetter weather.

With heat increasingly becoming a threat, cities ignoring the issue could eventually face even higher costs to react to each deadly heatwave. Taking action now to climate-proof older housing and better design new buildings will be cheaper and smarter in the long run.