Passive Daytime Radiative Cooling
Also known as: PDRC
PDRC combines high solar reflectivity with longwave thermal emission to limit heat gains and support heat loss. Some emission can reach space through relatively transparent atmospheric wavelengths. Below-air-temperature cooling is possible under suitable conditions, but depends on the material, weather and surrounding environment.
Scientific detail
PDRC limits absorbed shortwave sunlight while supporting longwave radiative heat loss, including within the approximately 8–13 μm atmospheric window. Atmospheric transmission and incoming longwave radiation vary with wavelength, humidity and clouds. Net cooling also depends on sensible heat exchange and conduction; emissivity is not the fraction of emitted energy escaping to space, and the effective radiative sky is not simply a 3 K sink.
Related terms
Radiative Cooling
Heat loss from any object by emitting thermal infrared radiation.
Atmospheric Window
A range of infrared wavelengths (roughly 8–13 μm) where the atmosphere absorbs relatively little of Earth's outgoing thermal radiation.
Solar Reflectance
The fraction of incoming solar energy a surface reflects across the sun's spectrum.
Thermal Emittance
How efficiently a surface releases heat as infrared radiation.
Albedo
The fraction of sunlight a surface reflects — 0 is black, 1 is a perfect mirror.
Reflective Cooling
Cooling by bouncing sunlight away from a surface before it can be absorbed as heat.
Where this concept shows up on MEER
Related projects
- Freetown, Sierra Leone
Reflective rooftops across informal settlements.
- California, USA
Rooftop mirror arrays measuring cooling potential.
- Pune, India
Rooftop reflective installations in dense urban housing.
Related publications
Related MEERTalks
- MEERTalks
Recorded conversations with scientists and partners.
Explore in topic hubs
Curated collections of MEER research, projects, publications and stories that feature this term.
Passive Cooling
Everything MEER publishes on passive cooling — reflective roofs, PDRC materials, canopies, reservoir systems, projects, publications and stories, gathered in one place.
Radiative Cooling & PDRC
PDRC materials, the atmospheric window, thermal emittance and the practical engineering of surfaces that radiate heat directly to deep space.