Super-insulating solid may soon help historical homes reach net-zero goals

Advances in the manufacturing process for aerogels, the lightest solids on Earth, could provide the most promising solution yet for one of the building industry’s biggest challenges. Aerogel-infused products – from coatings to stop heat gain from roofs to plasters to insulate the interiors of heritage buildings – would help hard-to-insulate homes get to net zero. These may soon be available, as start-ups in the UK and France move into commercial aerogel production. The UK has around 8 million homes with solid walls, the vast majority built before the 1920s. Insulating these homes is tricky; many face planning restrictions, which prevent them from adding external cladding, while internal cladding reduces floor space and can cause mould and damp issues. Lacking an obvious solution, most of these homes remain largely uninsulated and burn large quantities of gas for warmth during winter. Without retrofit work, it can be very expensive to install and run the zero-carbon heating solutions needed for the UK to achieve its net-zero target. Advertisement But aerogels are synthetic, ultra-lightweight materials that are exceptionally insulating, as well as being fire resistant – a major advantage over cladding – and breathable. “Aerogels are basically porous solids – they are solids with a lot of air inside,” says Wim Malfait at the Swiss Federal Laboratories for Materials Science and Technology (EMPA). Their unique structure means air molecules are effectively trapped between pores, dramatically slowing heat transfer, he says. On paper, that would make them the perfect material for building insulation. But aerogels have traditionally been expensive and polluting to manufacture, limiting their use largely to industrial plants, aviation and space technology. Now, start-ups in the UK and France claim they have developed new processes for manufacturing aerogels at lower cost and higher scale, which could unlock their wider use in building retrofit and construction. Aerogels are generally produced by first creating a nanoparticle gel – usually from silica – which then undergoes a carefully controlled drying process, known as supercritical drying, to preserve its pore structure. This stage is usually energy-intensive and can take days to complete. Thermulon, a UK start-up, says it has redesigned this production process to make use of cheaper materials, lower energy use and standardised equipment. “We developed a way to make aerogels using the cheapest materials and using equipment and methodology that allows you to go to big scale,” says Thermulon’s Sam Cryer. Thermulon has been working with UK plaster-maker Best of Lime to develop a specialist lime plaster containing aerogels, which could be used as an insulation material for historical solid-wall homes. Aerogel plaster could provide the most promising route to net zero for these homes, says Cryer. “This is a really exciting market for us,” he says. The company is also working on aerogels for insulation cladding, and EV battery packs, but Cryer says insulating plaster will probably be the first product to market. It’s finalising plans to start producing aerogels at commercial scale with a contract manufacturer in Northern Ireland next year, with the capability of producing 100 tonnes of aerogels per year in 2027. Meanwhile, French start-up Keey Aerogel has developed a way to make aerogels from silica waste from the construction industry, and using a continuously recycled solvent. The resulting product has a carbon footprint three times smaller than traditional aerogels, founder Francisco Ruiz says, while competing on cost. The firm is working with manufacturers of external renders to create an aerogel-infused mix to improve insulation performance and an aerogel-based “cool roof” coating. This would keep homes cooler in warmer months by reflecting sunlight and blocking heat entry. Keey is also working on an aerogel formula for wall cavity insulation, to be sold in the UK and Ireland. More effective cavity wall insulation will allow house builders to conform to tightening building standards without having to change the footprint of new homes or make rooms smaller, which would add cost and decrease their desirability, says Ruiz. The firm raised €18 million in venture capital – including backing from the French government – in 2025 to build its first commercial production plant. The plant, near Mulhouse in eastern France, will start production next year with the capability to produce 1000 to 2000 tonnes of aerogels per year. Aerogel insulation products for buildings will be expensive compared with traditional insulation options, even with advances to cut production costs. But for some buildings it may be the best option to enable low-carbon heating systems and shield against extreme weather. Malfait at EMPA says the technology is promising, but aerogel start-ups will need to focus on how to appeal to homeowners. “It may really be the best solution in many cases, but you have to get the customer over this initial price shock,” he says.