As anyone sweltering in the UK’s current heat wave can attest, the country’s housing stock is woefully under-heated.
Much of it is antiquated, dating back to when protection from cold and rain was the priority. Yet most new-build properties are also unprepared for what experts predict will be temperatures at the level of the summer 2018 peaks every other year by mid-century.
The Commission on Climate Change warned in a report last year that more than 570,000 residences had been built since 2016 that were not resistant to high temperatures – and neither were a further 1.5 million to be built in the next five years.
Government advisers accused ministers of failing to act to protect people from rising temperatures which “could even make many existing and new homes uninhabitable”.
The problem is deadly serious as vulnerable people struggle to stay cool in their own beds. The committee noted that the 2020 heatwave in England killed more than 2,500 people and warned that the number of heat-related deaths could triple by 2050.
Heat poses a threat not only to life, but also to the structural integrity of buildings, causing cracking of walls. In 2018 – the UK’s hottest summer overall on record along with 1976, 2003 and 2006 – there was a spike in subsidence as the soil beneath buildings dried and shrank, with more than 10,000 households subsequently making insurance claims on worth £64 million in just three months.
Critics blame homebuilders, developers and the government for being slow to react. “The housing industry is quite traditional and old-fashioned in adaptation and there are many challenges we need to address around zero carbon and future proofing,” says James Knight of design and engineering consultancy Arcadis.
So how can industry and government respond to the growing threat posed by high temperatures?
Refurbishment of old properties
The most obvious heat mitigation measure is air conditioning, but it is prohibitively expensive in terms of installation and running costs and works inefficiently in older, drafty homes. Energy-intensive systems also increase emissions—fueling global warming and worsening the overall problem.
Shuttering older homes – like this blue-painted house on Portobello Road, west London – is an effective way to keep out the sun. Photo: June Green/Alamy
Experts suggest the UK should learn from countries where extreme heat is more common, where homes have shutters or motorized blinds to keep out the sun and white surfaces to reflect the heat. Knight points out that around the Mediterranean, “people leave their homes closed all day, with the back windows open. How many of us leave the curtains closed on our south and west facing windows when we go to work on a sunny day?’
Similar “passive measures” requiring minimal energy and fuel use to cool homes include improving natural ventilation and increasing insulation, which has the dual benefit of reducing winter energy bills.
Heat design
There are even more effective measures that builders can introduce at the planning and construction stage: ensuring that the house and windows are oriented and positioned to limit exposure to direct sunlight; reduction of glazing; adding shade trees and plants; and installing an air source heat pump that can be used to both cool a home and heat it.
Other cooling features include wind catchers, roof-mounted devices inspired by Persian architecture that use the wind to bring fresh breezes into a room and expel stale air, and solar chimneys—tall, dark-surfaced structures designed to absorb sunlight radiation, creating a rising column of heated air, which in turn maintains the flow of the ventilation system.
The most advanced example of this principle is the “passive house,” an airtight, well-insulated building that relies almost entirely on passive measures such as sunlight, shading, and ventilation to maintain a constant temperature. They often have a ceiling ventilation unit with two air collectors: one for cool outdoor air and one for warm indoor air, which circulate around the home to maintain an even temperature.
“A passive house is the best solution when you have natural airflow through it,” says Bob Ward, vice-chairman of the London Climate Change Partnership. “This should become a guide on how to build for zero carbon emissions and zero overheating.”
Barratt’s Zed House, on the University of Salford campus, Manchester, is a pilot project testing technologies and features to achieve its zero carbon target by 2030. Photo: Barratt Developments
Meanwhile, Barratt, Britain’s biggest housebuilder, is trialling the Zed House, a zero-carbon concept home built in partnership with 40 industry partners and the University of Salford. It has an air source heat pump and 95 sensors to collect data in the home, including air quality. Barratt claims the pilot project is the first step towards delivering on the promise that all its new homes will be zero-carbon by 2030.
What about larger buildings?
Heat is not just a problem for domestic buildings – too many offices still rely on energy-intensive air conditioners and have large glass facades. “Huge glass buildings are just not a good idea – it’s a greenhouse,” says Ward. “You have to design the glass in a way that keeps the sun out.” Now there is a growing trend to install louvered windows in commercial buildings: parallel glass sliders in frames that can be opened or closed at an angle to improve ventilation.
Once again, countries in Europe are leading the way. The Edge, a modern office building built in Amsterdam for Deloitte in 2014, was cited as an example of how to reimagine workspaces. It features dynamic windows, automatic blinds, solar panels on the south side to keep out direct sunlight, underground heat storage pumps to pump hot or cold water into or out of the building and 28,000 sensors tracking movement, light levels , humidity and temperature.
What does the government do?
Until now, the UK’s focus on building efficiency has been on how to improve drafty homes, particularly in light of skyrocketing energy bills – but last year the government added an overheating section to building regulations for the first time, Part O, which came out went into effect last month. It urges builders to make reasonable arrangements to limit solar gains in summer and “provide adequate means of removing heat from the indoor environment”.
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However, the construction industry is not happy with the new rules, complaining that they could force already approved projects back to the drawing board. Stuart Baisley, executive chairman of the Federation of House Builders, wrote to the government in early June to complain that “the new regulations are fraught with impracticality and could require tens of thousands of homes with permission to go back through the planning process”. .
And what does Ward think of Part O? “It should help, although who knows how well it will be enforced,” he says.
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