Britain is baking again. But before the country bolts a cooling box to every wall, the construction industry needs to ask if it’s got it right about building design, says Sunil Pandita, chief division officer Planning & Design and Digital Twin Business Unit, Nemetschek Group
Soaring temperatures and wildfires were typically problems other countries suffered. For years, we’ve watched the Mediterranean and US west coast struggle with excessive summer heat but when Californian and French winemakers start buying land in southern England, you know something is up.
Climate change or climate crisis, call it what you will, but there is an undeniable fact that average global temperatures are rising. We have all experienced it over the past few years. Weather is changing and, as a result, we have to learn to change with it.
This summer has made the point with brutal efficiency. The UK is now in its third heatwave before mid-July. June delivered a new national record of 37.7C, and by 9 July the country had clocked more days above 34C than in any year since records began.
Somewhere around the third sleepless tropical night, most of the country arrived at the same question. Does Britain finally need air conditioning?
A hot country with a cold country’s buildings
It is a fair question. Only 4.3% of homes in England use air conditioning, according to recent research from the Energy Demand Research Centre, which is around a million properties in total.
The same researchers forecast that could reach 18m by 2050, while the Climate Change Committee estimates that 92% of existing UK homes are at risk of overheating by mid-century. The UK is, on any honest reading, a hot country with a cold country’s building stock.
But before we declare air conditioning the answer, look across the Channel. In the same week Britain sweltered, EDF shut down three nuclear reactors, at Golfech, Bugey and Chooz, because the rivers that cool them were too warm, taking roughly 6% of France’s nuclear capacity offline at the precise moment cooling demand peaked. It was the second time this summer. The French government had to grant an emergency exemption just to keep one plant discharging warm water into the Rhone.
The lesson here is that the grid is least able to deliver power exactly when a hot country needs it most. A national cooling strategy built on air conditioning alone assumes an abundance of cheap, reliable, low-carbon electricity on the hottest days of the year. This summer has proved that assumption wrong.
Designing cooling into buildings
So, the question for the UK is how much cooling can we design into buildings before reaching for the aircon? Every building now has to balance three competing demands: the comfort of the people inside it, the cost of running it and the carbon it produces. Air conditioning solves the first and inflates the other two.
More units mean more electricity, more electricity means higher bills and a bigger carbon footprint, and regulators are increasingly counting that footprint. What was once simply the right thing to do has become the economically right thing to do as well.
The good news is that this balance can be struck, but only at the design stage. The type of glazing, the roof, the orientation, the number of floors, the materials. Each choice changes how much heat a building absorbs and how much energy it will demand for the next 30 to 50 years. Every kilowatt of cooling designed out of a building is a kilowatt the grid never has to find in a heatwave.
The catch is that these trade-offs can only be made well if the right information is available at the moment the decision is taken. If carbon and thermal performance data takes three weeks to assemble, the decision gets made without it.
Push and pull. Regulation, data and total cost of ownership
Regulation is heading in this direction whether the industry is ready or not. In England, Part O of the Building Regulations already requires new homes to prioritise passive cooling measures before mechanical ones, though it stops at residential.
France has gone further, embedding whole-life carbon into its RE2020 rules for new construction, with further requirements in the pipeline that would oblige building owners to produce lifecycle carbon assessments on demand.
Other countries are drafting their own versions, so owners and developers who wait for the law to arrive will find themselves scrambling. Those who start asking their architects for whole-life carbon and thermal performance calculations now, covering operation as well as construction, will be ahead of it.
And here is where the UK industry should be honest with itself, because the evidence suggests it is not ready. A new report from Barbour ABI and GS1 UK estimates the sector loses up to £3.8bn a year to fragmented and inconsistent product data. Nearly all professionals surveyed know about the Building Safety Act, yet only 21% say they are fully prepared for it. Most striking of all, 84% report products being substituted on site.
Every unrecorded substitution, a different glazing unit here, a cheaper insulation product there, pulls a building’s real-world thermal performance away from what was designed and modelled. An industry that struggles to say what is actually in its walls has no hope of producing a whole-life carbon assessment at the click of a button.
The fix is to treat data as infrastructure rather than a byproduct. When the information generated during design and construction flows into operation, through a digital twin of the finished building, owners can see how the asset actually performs in a heatwave, compare it against design intent and make informed calls, such as whether to keep running an ageing HVAC system or invest in replacing it. Total cost of ownership, not build cost, becomes the measure that counts most.
There is a longer game too. Advances in material science, from greener concrete to better glazing, smarter HVAC design and lower-impact refrigerants, promise buildings that simply generate and trap less heat in the first place. That work is already under way in research partnerships between industry and universities, including the work we are doing with institutions in the US and Singapore.
So, does the UK need air conditioning? Some, yes, and for vulnerable people in overheating homes it will save lives. But we have the technology and know-how to do better with less.
Britain has spent two decades regulating to keep heat in. It now needs to design, build and manage for keeping heat out, and that starts with knowing, in data rather than in hindsight, exactly what we are building. We have to accept the UK is an increasingly hot country now. It is time it started designing like one.
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