It is presently challenging to efficiently cool enclosed spaces such as stationary automobiles that trap heat via the greenhouse effect. In a new report in Science Advances, Se-Yeon Heo and a team of scientists in materials science, engineering and nanoarchitectonics in Japan and the Republic of Korea, presented a Janus emitter (JET) for surface cooling. They used a silver (Ag)-polydimethylsiloxane (PDMS) layer on a micropatterned quartz substrate and the material allowed them to cool the space even when the JET was attached within an enclosure. As a result, the JET (Janus emitter) could passively mitigate the greenhouse effect in enclosures and offer surface cooling performance comparable to conventional radiative coolers.