New buildings can be designed for heat but with the oldest housing stock in Europe, the UK has a retrofit challenge ahead. Does the answer start with data or air conditioning, asks Sunil Pandita, chief division officer planning & design and digital twin business unit, Nemetschek Group
Another summer, another set of broken records. The UK was in its third heatwave before mid-July. June set a new national high of 37.7C, and the country has already logged more days above 34C than in any year since records began. Much of the debate that now follows will focus on how we design and build new buildings for a hotter climate. But to be honest, that is the easy bit. How we manage to cool older buildings sustainably is going to take a little more expertise.
The Climate Change Committee estimates that 92% of existing UK homes are at risk of overheating by mid-century, and the commercial and public estate is little better placed. The UK has the oldest housing stock in Europe. According to the Resolution Foundation, 38% of British homes were built before 1946, a higher share than any other European country and more than double the EU average. This is stock designed for a damp, mild climate that no longer exists, and no amount of clever new-build regulation will fix it.
The obvious answer is air conditioning. But is it the right answer?
Heritage buildings have a tendency to resist retrofit. Wet radiator heating systems make ducted cooling expensive to add. And every unit installed dumps its waste heat straight outside, pushing up temperatures on the street. It also adds demand to the grid. If everyone had air conditioning running throughout the summer, how would it cope?
Researchers at the University of Reading recently warned of a growing cooling divide and called for a national cooling strategy that puts refurbishment ahead of a rush to mechanical cooling. Around one million of England’s 25 million homes have air conditioning now, says the report with forecasts suggesting this could reach 18 million by 2050 as summers get hotter.
So, what is the alternative?
It’s increasingly accepted it’s about building knowledge, knowing everything there is to know because most older buildings are, in data terms, strangers to their own owners. Decades of undocumented modifications, drawings in filing cabinets, product information trapped in PDFs and maintenance histories scattered across systems. You cannot manage what you cannot see, and most building managers are running their assets half blind.
The technology to fix this has matured quickly. Laser scanning can capture an existing building as a point cloud and turn it into an accurate digital model in a fraction of the time it once took. Legacy drawings and documents can be digitised and linked to that model. Maintenance and asset records can be layered on top, mapping the gap between what was built and what is actually there today. Add live data from meters and sensors and the result is that you no longer have an analogue archive. It is a digital twin, a living picture of how the building really behaves.
In a heatwave, that picture can become crucial to the operation of a building. A digital twin fed with real-time data can show which zones overheat and when, and how heat changes through the building over the day. It can also show how HVAC is actually performing against its design intent. The digital twin can turn cooling from guesswork into scheduling, pre-cooling spaces overnight when electricity is cheaper and cleaner, managing occupancy and identifying any ageing, inefficient equipment.
It can also answer the question every facilities director eventually faces – ‘do we keep running this ageing plant, repair it, or replace it?’ Reaching a decision can be difficult and involve a number of factors based on experience but what if the data can actually give you a clearer indication? Instinct may suggest you sweat an asset but data can often say otherwise. Seen across a 30-to-50-year life, the capital cost of replacement is frequently the cheaper option, but only the numbers can prove it.
Does this work in practice? Barcelona suggests it does. The Hospital de la Santa Creu i Sant Pau occupies a UNESCO-listed Art Nouveau site, about as unforgiving an environment for retrofit as exists. Rather than rip anything out, the hospital deployed 140 smart meters and an energy management platform across the estate, giving its teams a real-time view of consumption for the first time.
The result was a 28% reduction in energy costs within six months, in a building where conventional refurbishment was never an option. If a century-old heritage hospital can do it, the average office block has no excuse.
Airports are heading the same way, using digital twins to combine operational, maintenance and environmental data across sprawling, energy-hungry estates, with Vienna Airport among them.
Of course, regulation will create pressure to change. France, for example, already obliges owners of existing commercial buildings to cut energy use against fixed deadlines. The trend across Europe now is for efficiency and carbon rules to also include the existing estate, not just new construction. Energy prices are doing the rest. Cooling an inefficient building through a six-week hot summer is going to be felt on the P&L.
None of this requires a building to be new, or even modern. It requires the building to be known, through real-time intelligence gathered via solutions like digital twins, BIM and, of course, AI. The comfort of occupants, the cost of running the asset and the carbon it emits are competing demands, and in older stock the only way to balance them is with accurate, current data about what the building is and how it performs. The smartest building in Britain this summer will not necessarily be the newest one. It will be the one that knows itself well enough to stay cool well into our warming future.