A roof coating film launched by adhesives and coatings specialist 3M at InnoTrans reflects more than 85% of incoming solar radiation and has cut vehicle interior temperatures by around 4.5°C in early trials, compared with painting roof panels white.

The 3M Cooling Film combines high solar reflectance with a thermal emittance of around 91%, which radiates absorbed heat away from the vehicle surface. According to 3M, the surface temperature of a plain white-painted panel runs around 5°C higher than a panel treated with the film.

Trials have taken place in South Korea, India, France and Spain. The measured 4.5°C reduction in interior temperature is a trial result; the associated cost saving — lower air-conditioning running costs — remains a projection, though 3M frames it as an increasingly significant factor for operators as average global temperatures rise. Air-conditioning load is a growing share of onboard energy consumption, and any reduction in heat ingress directly reduces the work the HVAC system must do.

The film has been developed to withstand harsh weather conditions, including heavy rain and dusty environments. Its easy-clean surface is intended to reduce maintenance costs over the application's life.

The company describes the product as 'conformable', meaning it wraps around roof-mounted equipment boxes rather than requiring an additional shielding panel. That removes a component, saves weight and eliminates a step from the installation process.

3M has also tested the film outside rail, equipping a large fleet of electric last-mile delivery vehicles in Arizona. These vehicles absorb heat while standing at each delivery point, and air-conditioning is less effective when the doors are open, making cab comfort a persistent problem for drivers.

'Horizontal applications are really tough', 3M's rail portfolio leader Rohit Ramdey told Railway Gazette International, adding that 'the harsher the environment, the better the film will work'.

3M is offering a five-year warranty for rail applications, but Ramdey puts the film's life expectancy at seven to eight years — a span that broadly matches the heavy overhaul interval for modern rolling stock. If that durability holds in service, operators could apply the film at one heavy overhaul and expect it to last through to the next, aligning the coating's lifecycle with established maintenance cycles rather than adding a new intermediate task.

The product enters a market where operators in hotter climates are already paying rising cooling costs, and the trial geography — from South Korean and Indian summers to Mediterranean conditions in France and Spain — suggests 3M is targeting exactly those networks where solar gain imposes the heaviest air-conditioning burden.