Summer afternoons can turn roofs, cars and other outdoor surfaces into heat traps that absorb and retain heat well after sunset. Even air conditioning, although effective, comes with added costs and extra strain on the electricity network. Researchers from the University of Cambridge and their collaborators set out to address that gap in a joint project. The solution, reported in the journal Advanced Science, came from a familiar material: cellulose acetate. This thin, porous film is made by chemically modifying wood pulp and is already used in products such as eyeglass frames and cigarette filters; it absorbed less than 5% of incoming sunlight.
That figure is important because limiting solar absorption helps reduce the amount of heat the material gains from sunlight. The researchers also tested the films outdoors, where surfaces coated with the material reached temperatures about 5°C below the surrounding air under suitable conditions.
